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1.  Kidney Function and Mortality in Octogenarians: Cardiovascular Health Study All Stars 
OBJECTIVES:
To examine the association between kidney function and all-cause mortality in octogenarians.
DESIGN:
Retrospective analysis of prospectively collected data.
SETTING:
Community.
PARTICIPANTS:
Serum creatinine and cystatin C were measured in 1,053 Cardiovascular Health Study (CHS) All Stars participants.
MEASUREMENTS:
Estimated glomerular filtration rate (eGFR) was determined using the Chronic Kidney Disease Epidemiology Collaboration creatinine (eGFRCR) and cystatin C one-variable (eGFRCYS) equations. The association between quintiles of kidney function and all-cause mortality was analyzed using unadjusted and adjusted Cox proportional hazards models.
RESULTS:
Mean age of the participants was 85, 64% were female, 66% had hypertension, 14% had diabetes mellitus, and 39% had prevalent cardiovascular disease. There were 154 deaths over a median follow-up of 2.6 years. The association between eGFRCR and all-cause mortality was U-shaped. In comparison with the reference quintile (64–75 mL/min per 1.73 m2), the highest (≥75 mL/min per 1.73 m2) and lowest (≤43 mL/min per 1.73 m2) quintiles of eGFRCR were independently associated with mortality (hazard ratio (HR) = 2.49, 95% confidence interval (CI) = 1.36–4.55; HR = 2.28, 95% CI = 1.26–4.10, respectively). The association between eGFRCYS and all-cause mortality was linear in those with eGFRCYS of less than 60 mL/min per 1.73 m2, and in the multivariate analyses, the lowest quintile of eGFRCYS (<52 mL/min per 1.73 m2) was significantly associated with mortality (HR = 2.04, 95% CI = 1.12–3.71) compared with the highest quintile (>0.88 mL/min per 1.73 m2).
CONCLUSION:
Moderate reduction in kidney function is a risk factor for all-cause mortality in octogenarians. The association between eGFRCR and all-cause mortality differed from that observed with eGFRCYS; the relationship was U-shaped for eGFRCR, whereas the risk was primarily present in the lowest quintile for eGFRCYS. J Am Geriatr Soc 2012.
doi:10.1111/j.1532-5415.2012.04046.x
PMCID: PMC3902776  PMID: 22724391
octogenarians; kidney function; mortality
2.  Modifiable Risk Factors for Pneumonia Requiring Hospitalization among Community-Dwelling Older Adults: The Health, Aging, and Body Composition Study 
Background
Pneumonia requiring hospitalization remains a major public health problem among community-dwelling older adults. Impaired oral hygiene is a modifiable risk factor for healthcare-associated pneumonia, but its role in community-acquired pneumonia is unclear.
Objectives
To identify novel modifiable risk factors, focusing on oral hygiene, for pneumonia requiring hospitalization among community-dwelling older adults.
Design
Prospective observational cohort study
Setting
Memphis, Tennessee and Pittsburgh, Pennsylvania
Participants
Of 3075 well-functioning community-dwelling adults aged 70–79 years enrolled in the Health, Aging, and Body Composition Study from 1997–1998, 1441 had complete data, dental exam within six months of baseline, and were eligible for this study.
Measurements
The primary outcome was pneumonia requiring hospitalization through 2008.
Results
Of 1441 participants, 193 were hospitalized for pneumonia. In a multivariable model, male gender (HR 2.07, 95%CI 1.51–2.83), white race (HR 1.44, 95%CI 1.03–2.01), history of pneumonia (HR 3.09, 95%CI 1.86–5.14), pack-years of smoking (HR 1.006, 95%CI 1.001–1.011), and percent predicted FEV1 (moderate vs. mild/normal lung function [HR 1.78, 95%CI 1.28–2.48], severe vs. mild/normal lung function [HR 2.90, 95%CI 1.51–5.57]) were non-modifiable risk factors for pneumonia. Incident mobility limitation (HR 1.77, 95%CI 1.32–2.38) and higher mean oral plaque score (HR 1.29, 95%CI 1.02–1.64) were modifiable risk factors for pneumonia. Average Attributable Fractions revealed that 11.5% of pneumonias were attributed to incident mobility limitation and 10.3% to mean oral plaque score ≥1.
Conclusion
Incident mobility limitation and higher mean oral plaque score were two modifiable risk factors attributable for 22% of pneumonias requiring hospitalization. These data suggest innovative opportunities for pneumonia prevention among community-dwelling older adults.
doi:10.1111/jgs.12325
PMCID: PMC3714374  PMID: 23772872
pneumonia; community-dwelling; risk factors
3.  Association of total and computed tomographic measures of regional adiposity with incident cancer risk: a prospective population-based study of older adults 
Obesity is associated with increased risk of many types of cancer. Less is known regarding associations between adipose depots and cancer risk. We aimed to explore relationships between adipose depots, risk of cancer and obesity-related cancer (per NCI definition) in participants initially aged 70–79 without prevalent cancer (1,179 men, 1,340 women), and followed for incident cancer for 13 years. Measures included body mass index (BMI), total adipose tissue from dual-energy X-ray absorptiometry and computed tomography measures: visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue (SAT), thigh intermuscular adipose tissue and thigh muscle attenuation (Hounsfield Unit, HU), low HU indicates fatty infiltration. Hazard ratios (HR) and 95% confidence intervals (CIs) were estimated by Cox proportional hazards regression adjusted for demographics, lifestyle variables and medical conditions. During follow-up 617 participants developed cancer of which 224 were obesity-related cancers. Total adipose tissue and VAT were positively associated with cancer risk among women (HR 1.14, 95% CI 1.01–1.30 per SD increase, HR 1.15, 95% CI 1.02–1.30 per SD increase). There were no associations with cancer risk among men. Total adipose tissue was positively associated with obesity-related cancer risk among women (HR 1.23, 95% CI 1.03–1.46 per SD increase). VAT was positively associated with obesity-related cancer risk among men (HR 1.30, 95% CI 1.06–1.60 per SD increase) and remained associated even with adjustment for BMI (HR 1.40, 95% CI 1.08–1.82 per SD increase). These findings provide insight into relationships between specific adipose depots and cancer risk and suggest differential relationships among men and women.
doi:10.1139/apnm-2013-0360
PMCID: PMC4071344  PMID: 24869972
Obesity; weight; adipose; body fat; cancer incidence; cancer risk; aging
5.  Genetic analysis of long-lived families reveals novel variants influencing high density-lipoprotein cholesterol 
Frontiers in Genetics  2014;5:159.
The plasma levels of high-density lipoprotein cholesterol (HDL) have an inverse relationship to the risks of atherosclerosis and cardiovascular disease (CVD), and have also been associated with longevity. We sought to identify novel loci for HDL that could potentially provide new insights into biological regulation of HDL metabolism in healthy-longevous subjects. We performed a genome-wide association (GWA) scan on HDL using a mixed model approach to account for family structure using kinship coefficients. A total of 4114 subjects of European descent (480 families) were genotyped at ~2.3 million SNPs and ~38 million SNPs were imputed using the 1000 Genome Cosmopolitan reference panel in MACH. We identified novel variants near-NLRP1 (17p13) associated with an increase of HDL levels at genome-wide significant level (p < 5.0E-08). Additionally, several CETP (16q21) and ZNF259-APOA5-A4-C3-A1 (11q23.3) variants associated with HDL were found, replicating those previously reported in the literature. A possible regulatory variant upstream of NLRP1 that is associated with HDL in these elderly Long Life Family Study (LLFS) subjects may also contribute to their longevity and health. Our NLRP1 intergenic SNPs show a potential regulatory function in Encyclopedia of DNA Elements (ENCODE); however, it is not clear whether they regulate NLRP1 or other more remote gene. NLRP1 plays an important role in the induction of apoptosis, and its inflammasome is critical for mediating innate immune responses. Nlrp1a (a mouse ortholog of human NLRP1) interacts with SREBP-1a (17p11) which has a fundamental role in lipid concentration and composition, and is involved in innate immune response in macrophages. The NLRP1 region is conserved in mammals, but also has evolved adaptively showing signals of positive selection in European populations that might confer an advantage. NLRP1 intergenic SNPs have also been associated with immunity/inflammasome disorders which highlights the biological importance of this chromosomal region.
doi:10.3389/fgene.2014.00159
PMCID: PMC4042684  PMID: 24917880
NALP1; lipids; genomewide association study; aging; familial longevity; family-based study
6.  Identification of heart rate–associated loci and their effects on cardiac conduction and rhythm disorders 
den Hoed, Marcel | Eijgelsheim, Mark | Esko, Tõnu | Brundel, Bianca J J M | Peal, David S | Evans, David M | Nolte, Ilja M | Segrè, Ayellet V | Holm, Hilma | Handsaker, Robert E | Westra, Harm-Jan | Johnson, Toby | Isaacs, Aaron | Yang, Jian | Lundby, Alicia | Zhao, Jing Hua | Kim, Young Jin | Go, Min Jin | Almgren, Peter | Bochud, Murielle | Boucher, Gabrielle | Cornelis, Marilyn C | Gudbjartsson, Daniel | Hadley, David | Van Der Harst, Pim | Hayward, Caroline | Heijer, Martin Den | Igl, Wilmar | Jackson, Anne U | Kutalik, Zoltán | Luan, Jian’an | Kemp, John P | Kristiansson, Kati | Ladenvall, Claes | Lorentzon, Mattias | Montasser, May E | Njajou, Omer T | O’Reilly, Paul F | Padmanabhan, Sandosh | Pourcain, Beate St. | Rankinen, Tuomo | Salo, Perttu | Tanaka, Toshiko | Timpson, Nicholas J | Vitart, Veronique | Waite, Lindsay | Wheeler, William | Zhang, Weihua | Draisma, Harmen H M | Feitosa, Mary F | Kerr, Kathleen F | Lind, Penelope A | Mihailov, Evelin | Onland-Moret, N Charlotte | Song, Ci | Weedon, Michael N | Xie, Weijia | Yengo, Loic | Absher, Devin | Albert, Christine M | Alonso, Alvaro | Arking, Dan E | de Bakker, Paul I W | Balkau, Beverley | Barlassina, Cristina | Benaglio, Paola | Bis, Joshua C | Bouatia-Naji, Nabila | Brage, Søren | Chanock, Stephen J | Chines, Peter S | Chung, Mina | Darbar, Dawood | Dina, Christian | Dörr, Marcus | Elliott, Paul | Felix, Stephan B | Fischer, Krista | Fuchsberger, Christian | de Geus, Eco J C | Goyette, Philippe | Gudnason, Vilmundur | Harris, Tamara B | Hartikainen, Anna-liisa | Havulinna, Aki S | Heckbert, Susan R | Hicks, Andrew A | Hofman, Albert | Holewijn, Suzanne | Hoogstra-Berends, Femke | Hottenga, Jouke-Jan | Jensen, Majken K | Johansson, Åsa | Junttila, Juhani | Kääb, Stefan | Kanon, Bart | Ketkar, Shamika | Khaw, Kay-Tee | Knowles, Joshua W | Kooner, Angrad S | Kors, Jan A | Kumari, Meena | Milani, Lili | Laiho, Päivi | Lakatta, Edward G | Langenberg, Claudia | Leusink, Maarten | Liu, Yongmei | Luben, Robert N | Lunetta, Kathryn L | Lynch, Stacey N | Markus, Marcello R P | Marques-Vidal, Pedro | Leach, Irene Mateo | McArdle, Wendy L | McCarroll, Steven A | Medland, Sarah E | Miller, Kathryn A | Montgomery, Grant W | Morrison, Alanna C | Müller-Nurasyid, Martina | Navarro, Pau | Nelis, Mari | O’Connell, Jeffrey R | O’Donnell, Christopher J | Ong, Ken K | Newman, Anne B | Peters, Annette | Polasek, Ozren | Pouta, Anneli | Pramstaller, Peter P | Psaty, Bruce M | Rao, Dabeeru C | Ring, Susan M | Rossin, Elizabeth J | Rudan, Diana | Sanna, Serena | Scott, Robert A | Sehmi, Jaban S | Sharp, Stephen | Shin, Jordan T | Singleton, Andrew B | Smith, Albert V | Soranzo, Nicole | Spector, Tim D | Stewart, Chip | Stringham, Heather M | Tarasov, Kirill V | Uitterlinden, André G | Vandenput, Liesbeth | Hwang, Shih-Jen | Whitfield, John B | Wijmenga, Cisca | Wild, Sarah H | Willemsen, Gonneke | Wilson, James F | Witteman, Jacqueline C M | Wong, Andrew | Wong, Quenna | Jamshidi, Yalda | Zitting, Paavo | Boer, Jolanda M A | Boomsma, Dorret I | Borecki, Ingrid B | Van Duijn, Cornelia M | Ekelund, Ulf | Forouhi, Nita G | Froguel, Philippe | Hingorani, Aroon | Ingelsson, Erik | Kivimaki, Mika | Kronmal, Richard A | Kuh, Diana | Lind, Lars | Martin, Nicholas G | Oostra, Ben A | Pedersen, Nancy L | Quertermous, Thomas | Rotter, Jerome I | van der Schouw, Yvonne T | Verschuren, W M Monique | Walker, Mark | Albanes, Demetrius | Arnar, David O | Assimes, Themistocles L | Bandinelli, Stefania | Boehnke, Michael | de Boer, Rudolf A | Bouchard, Claude | Caulfield, W L Mark | Chambers, John C | Curhan, Gary | Cusi, Daniele | Eriksson, Johan | Ferrucci, Luigi | van Gilst, Wiek H | Glorioso, Nicola | de Graaf, Jacqueline | Groop, Leif | Gyllensten, Ulf | Hsueh, Wen-Chi | Hu, Frank B | Huikuri, Heikki V | Hunter, David J | Iribarren, Carlos | Isomaa, Bo | Jarvelin, Marjo-Riitta | Jula, Antti | Kähönen, Mika | Kiemeney, Lambertus A | van der Klauw, Melanie M | Kooner, Jaspal S | Kraft, Peter | Iacoviello, Licia | Lehtimäki, Terho | Lokki, Marja-Liisa L | Mitchell, Braxton D | Navis, Gerjan | Nieminen, Markku S | Ohlsson, Claes | Poulter, Neil R | Qi, Lu | Raitakari, Olli T | Rimm, Eric B | Rioux, John D | Rizzi, Federica | Rudan, Igor | Salomaa, Veikko | Sever, Peter S | Shields, Denis C | Shuldiner, Alan R | Sinisalo, Juha | Stanton, Alice V | Stolk, Ronald P | Strachan, David P | Tardif, Jean-Claude | Thorsteinsdottir, Unnur | Tuomilehto, Jaako | van Veldhuisen, Dirk J | Virtamo, Jarmo | Viikari, Jorma | Vollenweider, Peter | Waeber, Gérard | Widen, Elisabeth | Cho, Yoon Shin | Olsen, Jesper V | Visscher, Peter M | Willer, Cristen | Franke, Lude | Erdmann, Jeanette | Thompson, John R | Pfeufer, Arne | Sotoodehnia, Nona | Newton-Cheh, Christopher | Ellinor, Patrick T | Stricker, Bruno H Ch | Metspalu, Andres | Perola, Markus | Beckmann, Jacques S | Smith, George Davey | Stefansson, Kari | Wareham, Nicholas J | Munroe, Patricia B | Sibon, Ody C M | Milan, David J | Snieder, Harold | Samani, Nilesh J | Loos, Ruth J F
Nature genetics  2013;45(6):621-631.
Elevated resting heart rate is associated with greater risk of cardiovascular disease and mortality. In a 2-stage meta-analysis of genome-wide association studies in up to 181,171 individuals, we identified 14 new loci associated with heart rate and confirmed associations with all 7 previously established loci. Experimental downregulation of gene expression in Drosophila melanogaster and Danio rerio identified 20 genes at 11 loci that are relevant for heart rate regulation and highlight a role for genes involved in signal transmission, embryonic cardiac development and the pathophysiology of dilated cardiomyopathy, congenital heart failure and/or sudden cardiac death. In addition, genetic susceptibility to increased heart rate is associated with altered cardiac conduction and reduced risk of sick sinus syndrome, and both heart rate–increasing and heart rate–decreasing variants associate with risk of atrial fibrillation. Our findings provide fresh insights into the mechanisms regulating heart rate and identify new therapeutic targets.
doi:10.1038/ng.2610
PMCID: PMC3696959  PMID: 23583979
7.  Candidate Gene Association Study of BMI-Related Loci, Weight, and Adiposity in Old Age 
Most genome-wide association studies are confined to middle-aged populations. It is unclear whether associations between single nucleotide polymorphisms (SNPs) and obesity persist in old age. We aimed to relate 10 body mass index (BMI)–associated SNPs to weight, BMI, % fat, visceral and subcutaneous adipose tissue in Health ABC and AGES-Reykjavik comprising 4,846 individuals of European Ancestry, and 1,139 African Americans over age 65. SNPs were scaled using effect estimates from candidate SNPs. In Health ABC, a SNP near GNPDA2 was modestly associated with weight and SAT area (p = .008, p = .001). Risk score (sum of scaled SNPs) was associated with weight, BMI, and SAT area (p < .0001 for all), but neither GNPDA2 nor risk score was associated with weight, BMI, visceral adippose tissue, subcutaneous adipose tissue, or % fat in AGES-Reykjavik. In African Americans, a SNP near SEC16B was weakly associated with weight (p = .04). In this sample of older adults, no BMI-associated SNPs were associated with weight or adiposity.
doi:10.1093/gerona/gls227
PMCID: PMC3660116  PMID: 23160366
Obesity; Aging; Genetics; SNPs.
8.  Mitochondrial DNA sequence associations with dementia and amyloid-β in elderly African Americans 
Neurobiology of aging  2013;35(2):442.e1-442.e8.
Mitochondrial dysfunction occurs early in the course of several neurodegenerative diseases, and is potentially related to increased oxidative damage and amyloid-β (Aβ) formation in Alzheimer’s disease. The goals of this study were to assess mtDNA sequence associations with dementia risk, 10-year cognitive change, and markers of oxidative stress and Aβ among 1089 African-Americans in the population-based Health, Aging, and Body Composition Study. Participants were free of dementia at baseline, and incidence was determined in 187 (18%) cases over 10 to 12 follow-up years. Haplogroup L1 participants were at increased risk for developing dementia (odds ratio = 1.88, 95% confidence interval = 1.23–2.88, p = 0.004), lower plasma Aβ42 levels (p = 0.03), and greater 10-year decline on the Digit Symbol Substitution Test (p = 0.04) when compared with common haplogroup L3. The p.V193I, ND2 substitution was associated with significantly higher Aβ42 levels (p = 0.0012), and this association was present in haplogroup L3 (p = 0.018) but not L1 (p = 0.90) participants. All associations were independent of potential confounders, including APOEε4 status and nuclear genetic ancestry. Identification of mtDNA sequence variation associated with dementia risk and cognitive decline may contribute to the development of new treatment targets and diagnostic tests that identify responders to interventions targeting mitochondria.
doi:10.1016/j.neurobiolaging.2013.05.023
PMCID: PMC4019378  PMID: 24140124
Dementia; Mitochondria; mtDNA; Amyloid-β; Oxidative stress
9.  Association of Major and Minor ECG Abnormalities With Coronary Heart Disease Events 
Context
In populations of older adults, prediction of coronary heart disease (CHD) events through traditional risk factors is less accurate than in middle-aged adults. Electrocardiographic (ECG) abnormalities are common in older adults and might be of value for CHD prediction.
Objective
To determine whether baseline ECG abnormalities or development of new and persistent ECG abnormalities are associated with increased CHD events.
Design, Setting, and Participants
A population-based study of 2192 white and black older adults aged 70 to 79 years from the Health, Aging, and Body Composition Study (Health ABC Study) without known cardiovascular disease. Adjudicated CHD events were collected over 8 years between 1997–1998 and 2006–2007. Baseline and 4-year ECG abnormalities were classified according to the Minnesota Code as major and minor. Using Cox proportional hazards regression models, the addition of ECG abnormalities to traditional risk factors were examined to predict CHD events.
Main Outcome Measure
Adjudicated CHD events (acute myocardial infarction [MI], CHD death, and hospitalization for angina or coronary revascularization).
Results
At baseline, 276 participants (13%) had minor and 506 (23%) had major ECG abnormalities. During follow-up, 351 participants had CHD events (96 CHD deaths, 101 acute MIs, and 154 hospitalizations for angina or coronary revascularizations). Both baseline minor and major ECG abnormalities were associated with an increased risk of CHD after adjustment for traditional risk factors (17.2 per 1000 person-years among those with no abnormalities; 29.3 per 1000 person-years; hazard ratio [HR], 1.35; 95% CI, 1.02–1.81; for minor abnormalities; and 31.6 per 1000 person-years; HR, 1.51; 95% CI, 1.20–1.90; for major abnormalities). When ECG abnormalities were added to a model containing traditional risk factors alone, 13.6% of intermediate-risk participants with both major and minor ECG abnormalities were correctly reclassified (overall net reclassification improvement [NRI], 7.4%; 95% CI, 3.1%–19.0%; integrated discrimination improvement, 0.99%; 95% CI, 0.32%–2.15%). After 4 years, 208 participants had new and 416 had persistent abnormalities. Both new and persistent ECG abnormalities were associated with an increased risk of subsequent CHD events (HR, 2.01; 95% CI, 1.33–3.02; and HR, 1.66; 95% CI, 1.18–2.34; respectively). When added to the Framingham Risk Score, the NRI was not significant (5.7%; 95% CI, −0.4% to 11.8%).
Conclusions
Major and minor ECG abnormalities among older adults were associated with an increased risk of CHD events. Depending on the model, adding ECG abnormalities was associated with improved risk prediction beyond traditional risk factors.
doi:10.1001/jama.2012.434
PMCID: PMC4006989  PMID: 22496264
10.  Mitochondrial DNA variation in human metabolic rate and energy expenditure 
Mitochondrion  2011;11(6):855-861.
The role of climate in driving selection of mtDNA as Homo sapiens migrated out of Africa into Eurasia remains controversial. We evaluated the role of mtDNA variation in resting metabolic rate (RMR) and total energy expenditure (TEE) among 294 older, community-dwelling African and European American adults from the Health, Aging and Body Composition Study. Common African haplogroups L0, L2 and L3 had significantly lower RMRs than European haplogroups H, JT and UK with haplogroup L1 RMR being intermediate to these groups. This study links mitochondrial haplogroups with ancestry-associated differences in metabolic rate and energy expenditure.
doi:10.1016/j.mito.2011.04.005
PMCID: PMC3998521  PMID: 21586348
Metabolic rate; Energetics; Mitochondria; Mitochondrial haplogroups; mtDNA; Oxidative phosphorylation
11.  Physical Activity and Years of Healthy Life in Older Adults: Results From the Cardiovascular Health Study 
Little is known about how many years of life and disability-free years seniors can gain through exercise. Using data from the Cardiovascular Health Study, the authors estimated the extra years of life and self-reported healthy life (over 11 years) and years without impairment in activities of daily living (over 6 years) associated with quintiles of physical activity (PA) in older adults from different age groups. They estimated PA from the Minnesota Leisure Time Activities Questionnaire. Multivariable linear regression adjusted for health-related covariates. The relative gains in survival and years of healthy life (YHL) generally were proportionate to the amount of PA, greater among those 75+, and higher in men. Compared with being sedentary, the most active men 75+ had 1.49 more YHL (95% CI: 0.79, 2.19), and the most active women 75+ had 1.06 more YHL (95% CI: 0.44, 1.68). Seniors over age 74 experience the largest relative gains in survival and healthy life from physical activity.
PMCID: PMC3978479  PMID: 20651417
aging; exercise; mortality; health status; activities of daily living
12.  Skeletal Muscle Mitochondrial Energetics Are Associated With Maximal Aerobic Capacity and Walking Speed in Older Adults 
Background.
Lower ambulatory performance with aging may be related to a reduced oxidative capacity within skeletal muscle. This study examined the associations between skeletal muscle mitochondrial capacity and efficiency with walking performance in a group of older adults.
Methods.
Thirty-seven older adults (mean age 78 years; 21 men and 16 women) completed an aerobic capacity (VO2 peak) test and measurement of preferred walking speed over 400 m. Maximal coupled (State 3; St3) mitochondrial respiration was determined by high-resolution respirometry in saponin-permeabilized myofibers obtained from percutanous biopsies of vastus lateralis (n = 22). Maximal phosphorylation capacity (ATPmax) of vastus lateralis was determined in vivo by 31P magnetic resonance spectroscopy (n = 30). Quadriceps contractile volume was determined by magnetic resonance imaging. Mitochondrial efficiency (max ATP production/max O2 consumption) was characterized using ATPmax per St3 respiration (ATPmax/St3).
Results.
In vitro St3 respiration was significantly correlated with in vivo ATPmax (r 2 = .47, p = .004). Total oxidative capacity of the quadriceps (St3*quadriceps contractile volume) was a determinant of VO2 peak (r 2 = .33, p = .006). ATPmax (r 2 = .158, p = .03) and VO2 peak (r 2 = .475, p < .0001) were correlated with preferred walking speed. Inclusion of both ATPmax/St3 and VO2 peak in a multiple linear regression model improved the prediction of preferred walking speed (r 2 = .647, p < .0001), suggesting that mitochondrial efficiency is an important determinant for preferred walking speed.
Conclusions.
Lower mitochondrial capacity and efficiency were both associated with slower walking speed within a group of older participants with a wide range of function. In addition to aerobic capacity, lower mitochondrial capacity and efficiency likely play roles in slowing gait speed with age.
doi:10.1093/gerona/gls196
PMCID: PMC3593613  PMID: 23051977
Muscle; Mitochondria; Aging; Walking speed.
13.  A Genome-Wide Association Study of Depressive Symptoms 
Hek, Karin | Demirkan, Ayse | Lahti, Jari | Terracciano, Antonio | Teumer, Alexander | Cornelis, Marilyn C. | Amin, Najaf | Bakshis, Erin | Baumert, Jens | Ding, Jingzhong | Liu, Yongmei | Marciante, Kristin | Meirelles, Osorio | Nalls, Michael A. | Sun, Yan V. | Vogelzangs, Nicole | Yu, Lei | Bandinelli, Stefania | Benjamin, Emelia J. | Bennett, David A. | Boomsma, Dorret | Cannas, Alessandra | Coker, Laura H. | de Geus, Eco | De Jager, Philip L. | Diez-Roux, Ana V. | Purcell, Shaun | Hu, Frank B. | Rimma, Eric B. | Hunter, David J. | Jensen, Majken K. | Curhan, Gary | Rice, Kenneth | Penman, Alan D. | Rotter, Jerome I. | Sotoodehnia, Nona | Emeny, Rebecca | Eriksson, Johan G. | Evans, Denis A. | Ferrucci, Luigi | Fornage, Myriam | Gudnason, Vilmundur | Hofman, Albert | Illig, Thomas | Kardia, Sharon | Kelly-Hayes, Margaret | Koenen, Karestan | Kraft, Peter | Kuningas, Maris | Massaro, Joseph M. | Melzer, David | Mulas, Antonella | Mulder, Cornelis L. | Murray, Anna | Oostra, Ben A. | Palotie, Aarno | Penninx, Brenda | Petersmann, Astrid | Pilling, Luke C. | Psaty, Bruce | Rawal, Rajesh | Reiman, Eric M. | Schulz, Andrea | Shulman, Joshua M. | Singleton, Andrew B. | Smith, Albert V. | Sutin, Angelina R. | Uitterlinden, André G. | Völzke, Henry | Widen, Elisabeth | Yaffe, Kristine | Zonderman, Alan B. | Cucca, Francesco | Harris, Tamara | Ladwig, Karl-Heinz | Llewellyn, David J. | Räikkönen, Katri | Tanaka, Toshiko | van Duijn, Cornelia M. | Grabe, Hans J. | Launer, Lenore J. | Lunetta, Kathryn L. | Mosley, Thomas H. | Newman, Anne B. | Tiemeier, Henning | Murabito, Joanne
Biological psychiatry  2013;73(7):10.1016/j.biopsych.2012.09.033.
Background
Depression is a heritable trait that exists on a continuum of varying severity and duration. Yet, the search for genetic variants associated with depression has had few successes. We exploit the entire continuum of depression to find common variants for depressive symptoms.
Methods
In this genome-wide association study, we combined the results of 17 population-based studies assessing depressive symptoms with the Center for Epidemiological Studies Depression Scale. Replication of the independent top hits (p < 1 × 10−5) was performed in five studies assessing depressive symptoms with other instruments. In addition, we performed a combined meta-analysis of all 22 discovery and replication studies.
Results
The discovery sample comprised 34,549 individuals (mean age of 66.5) and no loci reached genome-wide significance (lowest p = 1.05 × 10−7). Seven independent single nucleotide polymorphisms were considered for replication. In the replication set (n = 16,709), we found suggestive association of one single nucleotide polymorphism with depressive symptoms (rs161645, 5q21, p = 9.19 × 10−3). This 5q21 region reached genome-wide significance (p = 4.78 × 10−8) in the overall meta-analysis combining discovery and replication studies (n = 51,258).
Conclusions
The results suggest that only a large sample comprising more than 50,000 subjects may be sufficiently powered to detect genes for depressive symptoms.
doi:10.1016/j.biopsych.2012.09.033
PMCID: PMC3845085  PMID: 23290196
Center for Epidemiologic Studies Depression Scale; CHARGE consortium; depression; depressive symptoms; genetics; genome-wide association study; meta-analysis
14.  Associations of Total and High-Molecular-Weight Adiponectin with All-Cause and Cardiovascular Mortality in Older Persons: The Cardiovascular Health Study 
Circulation  2012;126(25):2951-2961.
Background
Adiponectin shows opposite associations with adverse outcomes in healthy middle-aged populations (lower risk), and cohorts with prevalent cardiovascular disease (CVD), heart failure (HF) or advanced age (higher risk).
Methods and Results
In a population-based study of older adults, we examined the relationships of total and high-molecular-weight (HMW) adiponectin with mortality among subgroups defined by baseline cardiovascular status: no CVD, HF or atrial fibrillation (AF) (Group 1); CVD but no HF/AF (Group 2); and HF/AF (Group 3). We found significant differences in the associations with all-cause mortality across the groups. The association in Group 1 was U-shaped; increasing levels of total adiponectin up to 12.4 mg/L were associated with lower mortality after adjustment for confounders (HR=0.81 per 1-SD [0.65–0.95]), but above this cutpoint, higher levels conferred greater risk (HR=1.19 [1.12–1.27]). Further adjustment for diabetes or insulin resistance, protection against which has been proposed to mediate adiponectin’s beneficial relationships with outcome, attenuated the association in the lower range. There was no significant association in Group 2, but in Group 3, total adiponectin showed a direct adjusted association. Additional adjustment for putative metabolic/inflammatory intermediates suggested a direct association for Group 2, and magnified the one for Group 3 (HR=1.31 [1.15–1.50]). Results were similar for HMW adiponectin, and for cardiovascular mortality.
Conclusions
Adiponectin exhibits distinct associations with mortality in elders, which shift from U-shaped to flat to direct with greater baseline cardiovascular dysfunction, but become more consistently adverse after accounting for metabolic/inflammatory factors presumed to be favorably regulated by the adipokine. These findings advance understanding of the adiponectin paradox as relates to older adults.
doi:10.1161/CIRCULATIONAHA.112.135202
PMCID: PMC3968250  PMID: 23159554
Adiponectin; Aging; Mortality
15.  Reproducibility of peroneal motor nerve conduction measurement in older adults 
Objective
While neuropathy is common in the elderly, nerve conduction (NC) reproducibility in older adults is not well-established. We sought to evaluate intraobserver reproducibility of peroneal motor NC measures in a diverse sample of older adults.
Methods
We measured peroneal motor NC amplitude and velocity in a subset of participants (mean age=82.9 ± 2.7, n=62, 50% female, 51.6% black, 35.5% DM) in the Health, Aging, and Body Composition Study. Using coefficients of variation (CVs), intraclass correlation coefficients (ICCs), and Bland Altman Plots, we compared two sets of measurements taken by the same examiner hours apart on the same day.
Results
Low CVs (2.15–4.24%) and moderate to high ICCs (0.75–0.99) were observed. No systematic variation was found across measures. Despite small numbers in some subgroups, we found no differences in reproducibility by diabetes, race, or study site.
Conclusion
NC measures have moderate to high intraobsever reproducibility in older adults and are not affected by diabetes, race, or gender.
Significance
These data provide evidence to support use of these measures in aging research.
doi:10.1016/j.clinph.2012.07.027
PMCID: PMC3562564  PMID: 23022036
Motor nerve conduction; aging; peripheral nerve function; reproducibility; diabetes
16.  Hypertension and Low HDL-Cholesterol were Associated with Reduced Kidney Function Across the Age Spectrum: A Collaborative Study 
Annals of epidemiology  2013;23(3):106-111.
Purpose
To determine if the associations among established risk factors and reduced kidney function vary by age.
Methods
We pooled cross-sectional data from 14,788 non-diabetics aged 40–100 years in 4 studies: Cardiovascular Health Study, Health, Aging, and Body Composition Study, Multi-Ethnic Study of Atherosclerosis, and Prevention of Renal and Vascular End-Stage Disease cohort.
Results
Hypertension and low HDL-cholesterol were associated with reduced cystatin C-based estimated glomerular filtration rate (eGFR) across the age spectrum. In adjusted analyses, hypertension was associated with a 2.3 (95% CI 0.1, 4.4), 5.1 (4.1, 6.1), and 6.9 (3.0, 10.4) mL/min/1.73 m2 lower eGFR in participants 40–59, 60–79, and 80+ years, respectively (p-value for interaction <0.001). The association of low HDL-cholesterol with reduced kidney function was also greater in the older age groups: 4.9 (3.5, 6.3), 7.1 (CI 6.0, 8.3), 8.9 (CI 5.4, 11.9) mL/min/1.73 m2 (p-value for interaction <0.001). Smoking and obesity were associated with reduced kidney function in participants under 80 years. All estimates of the potential population impact of the risk factors were modest.
Conclusions
Hypertension, obesity, smoking, and low HDL-cholesterol are modestly associated with reduced kidney function in non-diabetics. The associations of hypertension and HDL-cholesterol with reduced kidney function appear stronger in older adults.
doi:10.1016/j.annepidem.2012.12.004
PMCID: PMC3570601  PMID: 23313266
Chronic kidney insufficiency; aged; hypertension; cholesterol; obesity; smoking
17.  Subclinical Hypothyroidism and the Risk of Coronary Heart Disease and Mortality 
Context
Data regarding the association between subclinical hypothyroidism and cardiovascular disease outcomes are conflicting among large prospective cohort studies. This might reflect differences in participants’ age, sex, thyroid-stimulating hormone (TSH) levels, or preexisting cardiovascular disease.
Objective
To assess the risks of coronary heart disease (CHD) and total mortality for adults with subclinical hypothyroidism.
Data Sources and Study Selection
The databases of MEDLINE and EMBASE (1950 to May 31, 2010) were searched without language restrictions for prospective cohort studies with baseline thyroid function and subsequent CHD events, CHD mortality, and total mortality. The reference lists of retrieved articles also were searched.
Data Extraction
Individual data on 55 287 participants with 542 494 person-years of follow-up between 1972 and 2007 were supplied from 11 prospective cohorts in the United States, Europe, Australia, Brazil, and Japan. The risk of CHD events was examined in 25 977 participants from 7 cohorts with available data. Euthyroidism was defined as a TSH level of 0.50 to 4.49 mIU/L. Subclinical hypothyroidism was defined as a TSH level of 4.5 to 19.9 mIU/L with normal thyroxine concentrations.
Results
Among 55 287 adults, 3450 had subclinical hypothyroidism (6.2%) and 51 837 had euthyroidism. During follow-up, 9664 participants died (2168 of CHD), and 4470 participants had CHD events (among 7 studies). The risk of CHD events and CHD mortality increased with higher TSH concentrations. In age- and sex-adjusted analyses, the hazard ratio (HR) for CHD events was 1.00 (95% confidence interval [CI], 0.86–1.18) for a TSH level of 4.5 to 6.9 mIU/L (20.3 vs 20.3/1000 person-years for participants with euthyroidism), 1.17 (95% CI, 0.96–1.43) for a TSH level of 7.0 to 9.9 mIU/L (23.8/1000 person-years), and 1.89 (95% CI, 1.28–2.80) for a TSH level of 10 to 19.9 mIU/L (n=70 events/235; 38.4/1000 person-years; P<.001 for trend). The corresponding HRs for CHD mortality were 1.09 (95% CI, 0.91–1.30; 5.3 vs 4.9/1000 person-years for participants with euthyroidism), 1.42 (95% CI, 1.03–1.95; 6.9/1000 person-years), and 1.58 (95% CI, 1.10–2.27, n=28 deaths/333; 7.7/1000 person-years; P=.005 for trend). Total mortality was not increased among participants with subclinical hypothyroidism. Results were similar after further adjustment for traditional cardiovascular risk factors. Risks did not significantly differ by age, sex, or preexisting cardiovascular disease.
Conclusions
Subclinical hypothyroidism is associated with an increased risk of CHD events and CHD mortality in those with higher TSH levels, particularly in those with a TSH concentration of 10 mIU/L or greater.
doi:10.1001/jama.2010.1361
PMCID: PMC3923470  PMID: 20858880
18.  Risk Factors for Hospitalization Among Older Persons Newly Diagnosed with Heart Failure: The Cardiovascular Health Study 
Objective
To identify risk factors for the occurrence of all-cause hospitalizations among older persons following heart failure diagnosis, and to determine whether geriatric conditions would emerge as independent risk factors when evaluated in the context of other relevant clinical data.
Background
Efforts to reduce costs in heart failure have focused on hospital utilization, yet few studies have examined how geriatric conditions affect the long-term risk of hospitalization following heart failure diagnosis. With the aging of the heart failure population, geriatric conditions such as slow gait and muscle weakness are becoming increasingly common.
Methods
The study population included participants with incident heart failure from the Cardiovascular Health Study, a longitudinal study of community-living, older persons. Data were collected through annual examinations and medical record review. Anderson-Gill regression modeling was used to determine predictors of hospitalization after heart failure diagnosis.
Results
Of the 758 participants newly diagnosed with heart failure, the mean rate of hospitalization was 7.9 per 10 person-years (95% CI 7.4–8.4). Independent risk factors for occurrence of hospitalizations included depressed ejection fraction (HR 1.25, 95% CI 1.04–1.51), NYHA classes 3 or 4 (HR 1.32, 95% CI 1.11–1.57), diabetes mellitus (HR 1.36, 95% CI 1.13–1.64), chronic kidney disease (HR 1.32 95% CI 1.14–1.53), weak grip strength (HR 1.19, 95% CI 1.00–1.42), slow gait speed (HR 1.28 95% CI 1.06–1.55), and depression (HR 1.23, 95% CI 1.05–1.45).
Conclusions
Geriatric conditions are important, and potentially modifiable, risk factors for hospitalization in heart failure that should be routinely assessed at the time of heart failure diagnosis.
doi:10.1016/j.jacc.2012.11.027
PMCID: PMC3576871  PMID: 23391194
Heart Failure; Hospitalizations; Geriatric conditions
19.  European ancestry and resting metabolic rate in older African Americans 
Background/Objectives
Resting metabolic rate (RMR) contributes 60–80% of total energy expenditure and is consistently lower in populations of African descent compared with populations of European populations. Determination of European ancestry (EA) through SNP analysis would provide an initial step for identifying genetic associations that contribute to low RMR. We sought to evaluate the association between RMR and EA in African Americans.
Subjects/Methods
RMR was measured by indirect calorimetry in 141 African American men and women (aged 74.7 ± 3.0 years) enrolled in a substudy of the Health, Aging and Body Composition Study. Ancestry informative markers were used to estimate individual percent EA. Multivariate regression was used to assess the association between RMR and EA after adjustments for soft tissue fat-free mass (STFFM), fat mass, age, study site, physical activity level and sex.
Results
Mean EA was 23.8 ± 16% (range: 0.1% to 70.7%) and there were no differences by sex. Following adjustments, each percent EA was associated with a 1.6 kcal/day (95% Confidence interval: 0.42, 2.7 kcal/day) higher RMR (p = 0.008). This equates to a 160 kcal/day lower RMR in a population of completely African ancestry with one of completely European ancestry. Additional adjustment for trunk STFFM that partially accounts for high-metabolic rate organs did not affect this association.
Conclusions
European ancestry in African Americans is strongly associated with higher RMR. The data suggest that population differences in RMR may be due to genetic variants.
doi:10.1038/ejcn.2011.22
PMCID: PMC3915864  PMID: 21468093
Admixture; energy metabolism; body composition; genetic mapping
20.  Pulse wave velocity and cognitive decline in elders: The Health, Aging and Body Composition study 
Background and Purpose
Arterial stiffness is a measure of subclinical cardiovascular disease (CVD) and increases with age. This study examines the association between arterial stiffness and cognitive decline in a cohort of older adults.
Methods
2,488 subjects with baseline measure of arterial stiffness (mean age, 74.2 years; 52.3% women) were prospectively followed over 9 years in the Health, Aging and Body Composition study. Arterial stiffness was measured as pulse wave velocity (PWV) and analyzed in tertiles. Cognitive function was assessed using the Modified Mini-Mental State Exam (3MS) at baseline and repeated at years 3, 5, 8 and 10. Lower 3MS scores indicate worse function. We fit linear mixed models to examine longitudinal changes in cognitive function over the 9 years of follow-up and logistic regression models, restricted to 1,331 participants, to examine cognitive impairment defined as a decrease of ≥5 points after 9 years. We adjusted for socio-demographics, Apoe4 and CVD risk factors.
Results
The annual decrease in 3MS scores was 0.30 points at low PWV (95%CI=−0.37;-0.22), 0.46 points at middle PWV (95%CI=−0.54;-0.39) and 0.45 points at high PWV (95%CI=−0.53;-0.38), from fully-adjusted linear mixed models. In fully-adjusted models, the odds of cognitive impairment after 9 years of follow-up was 40% greater for subjects with middle PWV (OR=1.40; 95% CI=1.03; 1.92) and 59% greater for subjects with high PWV (OR=1.59; 95% CI=1.16; 2.18), compared to low PWV.
Conclusions
High arterial stiffness was modestly associated with cognitive decline and impairment. Interventions to prevent arterial stiffness may be effective in delaying cognitive decline.
doi:10.1161/STROKEAHA.112.673533
PMCID: PMC3572783  PMID: 23321445
21.  Adverse Oral Health and Cognitive Decline: The Health, Aging and Body Composition Study 
Background/Objectives
Periodontal disease has been associated with poorer cross-sectional cognitive function and is correlated with adverse vascular outcomes, but has received little prospective investigation in relation to cognitive decline.
Design
Analysis of a prospective cohort study.
Setting
The Health, Aging and Body Composition (Health ABC) Study
Participants and measurements
We examined the prospective association between a range of oral health parameters and cognitive function using data on 1053 participants who were administered the Modified Mini-Mental State Examination (3MS) at year 1 (baseline) and year 3, and had participated in a comprehensive periodontal examination at year 2. We investigated 3MS decline from year 3 to 5 in 947 (89.9%) participants. Covariates included age, sex, education, race, cardiovascular disease/risk and depressive symptoms.
Results
Most indicators of adverse oral health at year 2 were associated with cognitive impairment based on averaged 3MS scores <80 for years 1 and 3, but these associations were substantially confounded by education and race. Higher gingival index, a measure of gingival inflammation, at year 2 remained independently associated with this definition of cognitive impairment and, in fully adjusted analyses, was also an independent predictor of a 5+ point cognitive decline from years 3 to 5.
Conclusion
Periodontitis may be a risk factor for cognitive decline. Gingivitis is reversible and periodontitis to some degree is preventable and controllable when manifest. Therefore, further research is needed to clarify potential underlying mechanisms and oral health interventions that potentially might ameliorate cognitive decline.
doi:10.1111/jgs.12094
PMCID: PMC3578234  PMID: 23405916
cognitive decline; cognitive impairment; periodontitis; periodontal diseases; gingivitis
22.  Subclinical Thyroid Dysfunction and the Risk of Heart Failure Events: An Individual Participant Data Analysis from Six Prospective Cohorts 
Circulation  2012;126(9):10.1161/CIRCULATIONAHA.112.096024.
Background
ACC/AHA Guidelines for the Diagnosis and Management of Heart Failure (HF) recommend investigating exacerbating conditions, such as thyroid dysfunction, but without specifying impact of different TSH levels. Limited prospective data exist regarding the association between subclinical thyroid dysfunction and HF events.
Methods and Results
We performed a pooled analysis of individual participant data using all available prospective cohorts with thyroid function tests and subsequent follow-up of HF events. Individual data on 25,390 participants with 216,248 person-years of follow-up were supplied from 6 prospective cohorts in the United States and Europe. Euthyroidism was defined as TSH 0.45–4.49 mIU/L, subclinical hypothyroidism as TSH 4.5–19.9 mIU/L and subclinical hyperthyroidism as TSH <0.45 mIU/L, both with normal free thyroxine levels. Among 25,390 participants, 2068 had subclinical hypothyroidism (8.1%) and 648 subclinical hyperthyroidism (2.6%). In age- and gender-adjusted analyses, risks of HF events were increased with both higher and lower TSH levels (P for quadratic pattern <0.01): hazard ratio (HR) was 1.01 (95% confidence interval [CI] 0.81–1.26) for TSH 4.5–6.9 mIU/L, 1.65 (CI 0.84–3.23) for TSH 7.0–9.9 mIU/L, 1.86 (CI 1.27–2.72) for TSH 10.0–19.9 mIUL/L (P for trend <0.01), and was 1.31 (CI 0.88–1.95) for TSH 0.10–0.44 mIU/L and 1.94 (CI 1.01–3.72) for TSH <0.10 mIU/L (P for trend = 0.047). Risks remained similar after adjustment for cardiovascular risk factors.
Conclusions
Risks of HF events were increased with both higher and lower TSH levels, particularly for TSH ≥10 mIU/L and for TSH <0.10 mIU/L.
doi:10.1161/CIRCULATIONAHA.112.096024
PMCID: PMC3884576  PMID: 22821943
cohort study; epidemiology; heart failure; meta-analysis; thyroid
23.  AORTIC PULSE WAVE VELOCITY PREDICTS FOCAL WHITE MATTER HYPERINTENSITIES IN A BIRACIAL COHORT OF OLDER ADULTS 
Hypertension  2012;61(1):160-165.
While the cross-sectional relationship of arterial stiffness with cerebral small vessel disease is consistently shown in middle-aged and young-old adults, its less clear if these associations remain significant over time in very old adults. We hypothesize that arterial stiffness is longitudinally associated with white matter characteristics and associations are stronger within watershed areas.
Neuroimaging was obtained in 2006–08 from 303 elderly (mean age 82.9 years, 59% women, 41% black) with pulse wave velocity measures in 1997–98. Multivariable regression models estimated the coefficients for pulse wave velocity (cm/sec) in relationship to presence, severity and spatial distribution of white matter hyperintensities, gray matter volume and fractional anisotropy from diffusion tensor, adjusting for demographic, cardiovascular risk factors and diseases from 1997–98 to 2006–08.
Higher pulse wave velocity in 1997–98 was associated with greater white matter hyperintensities volume in 2006–08 within the left superior longitudinal fasciculus (age and total brain white matter hyperintensities-adjusted p=0.023), but not with white matter hyperintensities in other tracts, or with fractional anisotropy or gray matter volume from total brain (p>0.2). Associations were stronger in blacks than in whites remaining significant in fully adjusted models.
Elderly with white matter hyperintensities in tracts related to processing speed and memory are more likely to have had higher pulse wave velocity values ten years prior, before neuroimaging data being available. Future studies should address whether arterial stiffness can serve as an early biomarker of covert brain structural abnormalities and whether early arterial stiffness control can promote successful brain aging, especially in black elderly.
doi:10.1161/HYPERTENSIONAHA.112.198069
PMCID: PMC3521843  PMID: 23172923
pulse wave velocity; small vessel disease; longitudinal; fractional anisotropy; community-dwelling elderly
24.  Plasma Beta Amyloid Level and Depression in Older Adults 
Background.
Older adults with depression have an increased risk of developing dementia. Low plasma beta-amyloid 42 (Aβ42) and Aβ42/Aβ40 have emerged as promising biomarkers of dementia. The association between depression and plasma Aβ is unclear.
Methods.
In this longitudinal study of 988 community-dwelling elders from the Health Aging and Body Composition study, depression was assessed with the Center for Epidemiologic Studies-Depression Scale 10-item version. We determined the association between Aβ42 and Aβ42/Aβ40 tertile and depression at baseline and over 9 years. We also stratified the models to determine if apolipoprotein E e4 allele status modified the associations.
Results.
Mean baseline age was 74.0 ± 3.0 years, 51 (5.2%) participants had depression, 545 (55.2%) were women, 531 (53.7%) were black, and 286 (30.7%) had one or more apolipoprotein E e4 allele. At baseline, there was no association between Aβ42/Aβ40 or Aβ42 and depression. Over 9 years, 220 (23.5%) participants developed depression. In adjusted Cox proportional hazards models, among those with one or more e4 allele, low Aβ42/Aβ40 was associated with an increased risk of developing depression over time (low 10.8% vs high 3.2%, hazard ratio = 2.38, 95% confidence interval: 1.15–4.92). Among those with no e4 allele, there was no association between Aβ42/Aβ40 and risk of depression over time (13.3% vs 17.5%, hazard ratio = 0.80, 95% confidence interval: 0.52–1.23; p value for interaction = .003).
Conclusions.
The association between low plasma Aβ42/Aβ40 and increased risk of incident depression among those with one or more apolipoprotein E e4 allele implies a synergistic relationship similar to that found with dementia. Future work should investigate the interrelationships among plasma Aβ42/Aβ40, depression, and dementia.
doi:10.1093/gerona/gls093
PMCID: PMC3598362  PMID: 22499763
Depression; Epidemiology; Plasma beta amyloid
25.  A variant of sparse partial least squares for variable selection and data exploration 
When data are sparse and/or predictors multicollinear, current implementation of sparse partial least squares (SPLS) does not give estimates for non-selected predictors nor provide a measure of inference. In response, an approach termed “all-possible” SPLS is proposed, which fits a SPLS model for all tuning parameter values across a set grid. Noted is the percentage of time a given predictor is chosen, as well as the average non-zero parameter estimate. Using a “large” number of multicollinear predictors, simulation confirmed variables not associated with the outcome were least likely to be chosen as sparsity increased across the grid of tuning parameters, while the opposite was true for those strongly associated. Lastly, variables with a weak association were chosen more often than those with no association, but less often than those with a strong relationship to the outcome. Similarly, predictors most strongly related to the outcome had the largest average parameter estimate magnitude, followed by those with a weak relationship, followed by those with no relationship. Across two independent studies regarding the relationship between volumetric MRI measures and a cognitive test score, this method confirmed a priori hypotheses about which brain regions would be selected most often and have the largest average parameter estimates. In conclusion, the percentage of time a predictor is chosen is a useful measure for ordering the strength of the relationship between the independent and dependent variables, serving as a form of inference. The average parameter estimates give further insight regarding the direction and strength of association. As a result, all-possible SPLS gives more information than the dichotomous output of traditional SPLS, making it useful when undertaking data exploration and hypothesis generation for a large number of potential predictors.
doi:10.3389/fninf.2014.00018
PMCID: PMC3939647  PMID: 24624079
high-dimensional; multicollinearity; over-fitting; SPLS; inference; tuning parameters; network; MRI

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