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1.  Modeling Bivariate Longitudinal Hormone Profiles by Hierarchical State Space Models 
The hypothalamic-pituitary-adrenal (HPA) axis is crucial in coping with stress and maintaining homeostasis. Hormones produced by the HPA axis exhibit both complex univariate longitudinal profiles and complex relationships among different hormones. Consequently, modeling these multivariate longitudinal hormone profiles is a challenging task. In this paper, we propose a bivariate hierarchical state space model, in which each hormone profile is modeled by a hierarchical state space model, with both population-average and subject-specific components. The bivariate model is constructed by concatenating the univariate models based on the hypothesized relationship. Because of the flexible framework of state space form, the resultant models not only can handle complex individual profiles, but also can incorporate complex relationships between two hormones, including both concurrent and feedback relationship. Estimation and inference are based on marginal likelihood and posterior means and variances. Computationally efficient Kalman filtering and smoothing algorithms are used for implementation. Application of the proposed method to a study of chronic fatigue syndrome and fibromyalgia reveals that the relationships between adrenocorticotropic hormone and cortisol in the patient group are weaker than in healthy controls.
doi:10.1080/01621459.2013.830071
PMCID: PMC3979568  PMID: 24729646
Circadian rhythm; Feedback Relationship; HPA axis; Kalman filter; Periodic splines
2.  Physical Performance and Frailty in Chronic Kidney Disease 
American journal of nephrology  2013;38(4):307-315.
Background
Poor physical performance and frailty are associated with elevated risks of death and disability. Chronic kidney disease (CKD) is also strongly associated with these outcomes. The risks of poor physical performance and frailty among CKD patients, however, are not well established.
Methods
We measured the Short Physical Performance Battery (SPPB, a summary test of gait speed, chair-raises and balance; range 0–12) and the five elements of frailty among 1111 Chronic Renal Insufficiency Cohort participants. Adjusting for demographics and multiple comorbidities, we fit a linear regression model for the outcome of SPPB score and an ordinal logistic regression model for frailty status.
Results
Median (interquartile range [IQR]) age was 65 (57–71) years, median estimated glomerular filtration rate (eGFR) for non-dialysis patients was 49 (36–62) ml/min/1.73m2, and median SPPB score was 9 (7–10). Seven percent of participants were frail and 43% were pre-frail. Compared with the SPPB score for eGFR >60 ml/min/1.73m2, the SPPB was 0.51 points lower for eGFR 30 – 59; 0.61 points lower for eGFR 15 – 29; and 1.75 points lower for eGFR <15; (p<0.01 for all comparisons). eGFR 30 – 59 (OR 1.45; p=0.024), eGFR 15 – 29 (OR 2.02; p=0.002) and eGFR <15 (OR 4.83, p<0.001) were associated with worse frailty status compared with eGFR >60 ml/min/1.73m2.
Conclusions
CKD severity was associated with poor physical performance and frailty in a graded fashion. Future trials should determine if outcomes for CKD patients with frailty and poor physical performance are improved by targeted interventions.
doi:10.1159/000355568
PMCID: PMC4019506  PMID: 24107579
Physical performance; frailty; chronic kidney disease
3.  Hyperglycemia is Associated with the Incidence of Frailty and Lower Extremity Mobility Limitations in Older Women 
Objectives
To determine the degree to which hyperglycemia predicts the development of frailty and/or lower extremity mobility limitations.
Design
Secondary data analysis of longitudinal data collected in a prospective cohort study.
Setting
Baltimore, Maryland
Participants
We examined 329 women from the Women’s Health and Aging Studies II aged 70–79 years at baseline who had all variables needed for analysis.
Methods
Hemoglobin A1c [HbA1c] at baseline was the independent variable and categorized as: <5.5%, 5.5 to 5.9%, 6.0–6.4%, 6.5–7.9%, ≥8%. The incidence of frailty and lower extremity mobility limitations (based on self-reported walking difficulty, walking speed, and short performance physical battery [SPPB] score) was determined (follow-up≈9 years). Frailty was assessed using the Cardiovascular Health Study criteria. Covariates included demographics, body mass index, interleukin-6, and clinical history of comorbidities. Statistical analyses included Kaplan-Meier survival curves and Cox regression models adjusting for key covariates.
Results
In time-to-event analyses, HbA1c category was associated with incidence of walking difficulty (p=0.049) and low physical performance (p=0.001); association with incidence of frailty and low walking speed had a trend towards significance (both p=0.10). In demographics-adjusted regression models, HbA1c≥8% (versus<5.5%) was associated with an approximately three-times increased risk of incident frailty and three-to-five times increased risk of lower extremity mobility limitations (all p<0.05). In fully adjusted models, HbA1c≥8% (versus<5.5%) was associated with incident frailty (hazard ratio[HR]=3.33, 95% confidence interval=1.24–8.93), walking difficulty (HR=3.47,1.26–9.55), low walking speed (HR=2.82,1.19–6.71), and low physical performance (HR=3.60,1.52–8.53).
Conclusions
Hyperglycemia is associated with the development of frailty and lower extremity mobility limitations in older women; future studies should identify mediators of these relationships.
doi:10.1111/j.1532-5415.2012.04099.x
PMCID: PMC4144067  PMID: 22882211
Hyperglycemia; Elderly; Frailty; Mobility; Disability
4.  Genome-wide association study of age at menarche in African-American women 
Human Molecular Genetics  2013;22(16):3329-3346.
African-American (AA) women have earlier menarche on average than women of European ancestry (EA), and earlier menarche is a risk factor for obesity and type 2 diabetes among other chronic diseases. Identification of common genetic variants associated with age at menarche has a potential value in pointing to the genetic pathways underlying chronic disease risk, yet comprehensive genome-wide studies of age at menarche are lacking for AA women. In this study, we tested the genome-wide association of self-reported age at menarche with common single-nucleotide polymorphisms (SNPs) in a total of 18 089 AA women in 15 studies using an additive genetic linear regression model, adjusting for year of birth and population stratification, followed by inverse-variance weighted meta-analysis (Stage 1). Top meta-analysis results were then tested in an independent sample of 2850 women (Stage 2). First, while no SNP passed the pre-specified P < 5 × 10−8 threshold for significance in Stage 1, suggestive associations were found for variants near FLRT2 and PIK3R1, and conditional analysis identified two independent SNPs (rs339978 and rs980000) in or near RORA, strengthening the support for this suggestive locus identified in EA women. Secondly, an investigation of SNPs in 42 previously identified menarche loci in EA women demonstrated that 25 (60%) of them contained variants significantly associated with menarche in AA women. The findings provide the first evidence of cross-ethnic generalization of menarche loci identified to date, and suggest a number of novel biological links to menarche timing in AA women.
doi:10.1093/hmg/ddt181
PMCID: PMC3723312  PMID: 23599027
5.  Subclinical Thyroid Dysfunction and Incident Hip Fracture in Older Adults 
Archives of internal medicine  2010;170(21):1876-1883.
Background
Subclinical thyroid dysfunction is common in older adults and affects bone metabolism, but its effects on fracture risk have not been reported. We sought to determine prospectively whether older men and women with subclinical hyperthyroidism or hypothyroidism have an increased risk of hip fracture.
Methods
Prospective cohort of 3567 US community-dwelling adults, 65 years or older, with biochemically defined subclinical thyroid dysfunction or euthyroidism was enrolled from June 10, 1989, through May 30, 1990, and followed up through 2004. Main outcome measures included incidence and hazard ratios (HRs), with 95% confidence intervals (CIs), of confirmed incident hip fractures for groups with subclinical hypothyroidism, subclinical hyperthyroidism, and euthyroidism as defined at baseline.
Results
During 39 952 person-years (median follow-up, 13 years), hip fracture incidence (per 1000 men-years) was 13.65 in men with subclinical hyperthyroidism (n = 29) and 10.27 in men with subclinical hypothyroidism (n = 184), both greater than 5.0 in men with euthyroidism (n = 1159). Men with subclinical hypothyroidism had a multivariable-adjusted HR of 2.31 (95% CI, 1.25–4.27); those with subclinical hyperthyroidism, 3.27 (0.99–11.30). After excluding those with baseline use of thyroid-altering medications, men with endogenous subclinical hyperthyroidism had a higher HR of 4.91 (95% CI, 1.13–21.27), as did men with endogenous subclinical hypothyroidism (2.45, 1.27–4.73). Hip fracture incidence (per 1000 women-years) was 8.93 in women with subclinical hypothyroidism (n = 359) and 10.90 in women with subclinical hyperthyroidism (n = 142) compared with 10.18 in women with euthyroidism (n = 1694). No clear association between subclinical dysfunction and fracture was observed in women.
Conclusions
Older men with subclinical hyperthyroidism or hypothyroidism are at increased risk for hip fracture. Whether treatment of the subclinical syndrome reduces this risk is unknown.
doi:10.1001/archinternmed.2010.424
PMCID: PMC4122328  PMID: 21098345
6.  Resting Metabolic Rate Among Old-Old Women With and Without Frailty: Variability and Estimation of Energy Requirements 
Objectives
Resting metabolic rate (RMR) is the largest component of total energy expenditure. It has not been studied in old-old adults living in the community, though abnormalities in RMR may play a critical role in the development of the clinical syndrome of frailty. The objective was to measure RMR and examine the association of measured RMR with frailty status and compare it to expected RMR generated by a predictive equation.
Design
Physiologic sub-study conducted as a home visit within an observational cohort study.
Setting
Baltimore City and County, Maryland.
Participants
77 women age 83–93 years enrolled in the Women’s Health and Aging Study II.
Measurements
RMR with indirect calorimetry; frailty status; fat-free mass; ambient and body temperature; expected RMR via the Mifflin-St. Jeor equation.
Results
Average RMR was 1119 kcal/d (s.d.± 205; range 595–1560). Agreement between observed and expected RMR was biased and very poor (between-subject coefficient of variation 38.0%, 95%CI: 35.1–40.8). Variability of RMR was increased in frail subjects (heteroscedasticity F test P value=0.02). Both low and high RMR were associated with being frail (Odds Ratio 5.4, P value=0.04) and slower self-selected walking speed (P value<0.001) after adjustment for covariates.
Conclusion
Equations to predict RMR that are not validated in old-old adults appear to correlate poorly with measured RMR. RMR values are highly variable among old-old women, with deviations from the mean predicting clinical frailty. These exploratory findings suggest a pathway to clinical frailty through either high or low RMR.
doi:10.1111/j.1532-5415.2012.04101.x
PMCID: PMC3458581  PMID: 22985142
resting metabolic rate; frailty; older adults
7.  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
8.  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
9.  Subclinical Hyperthyroidism and the Risk of Coronary Heart Disease and Mortality 
Archives of internal medicine  2012;172(10):10.1001/archinternmed.2012.402.
Background
Data from prospective cohort studies regarding the association between subclinical hyperthyroidism and cardiovascular outcomes are conflicting. We aimed to assess the risks of total and coronary heart disease (CHD) mortality, CHD events, and atrial fibrillation (AF) associated with endogenous subclinical hyperthyroidism among all available large prospective cohorts.
Methods
Individual data on 52 674 participants were pooled from 10 cohorts. Coronary heart disease events were analyzed in 22 437 participants from 6 cohorts with available data, and incident AF was analyzed in 8711 participants from 5 cohorts. Euthyroidism was defined as thyrotropin level between 0.45 and 4.49 mIU/L and endogenous subclinical hyperthyroidism as thyrotropin level lower than 0.45 mIU/L with normal free thyroxine levels, after excluding those receiving thyroid-altering medications.
Results
Of 52 674 participants, 2188 (4.2%) had subclinical hyperthyroidism. During follow-up, 8527 participants died (including 1896 from CHD), 3653 of 22 437 had CHD events, and 785 of 8711 developed AF. In age-and sex-adjusted analyses, subclinical hyperthyroidism was associated with increased total mortality (hazard ratio [HR], 1.24, 95% CI, 1.06–1.46), CHD mortality (HR, 1.29; 95% CI, 1.02–1.62), CHD events (HR, 1.21; 95% CI, 0.99–1.46), and AF (HR, 1.68; 95% CI, 1.16–2.43). Risks did not differ significantly by age, sex, or preexisting cardiovascular disease and were similar after further adjustment for cardiovascular risk factors, with attributable risk of 14.5% for total mortality to 41.5% for AF in those with subclinical hyperthyroidism. Risks for CHD mortality and AF (but not other outcomes) were higher for thyrotropin level lower than 0.10 mIU/L compared with thyrotropin level between 0.10 and 0.44 mIU/L (for both, P value for trend, ≤.03).
Conclusion
Endogenous subclinical hyperthyroidism is associated with increased risks of total, CHD mortality, and incident AF, with highest risks of CHD mortality and AF when thyrotropin level is lower than 0.10 mIU/L.
doi:10.1001/archinternmed.2012.402
PMCID: PMC3872478  PMID: 22529182
10.  Predictors of Thyroid Hormone Initiation in Older Adults: Results From the Cardiovascular Health Study 
Background.
Despite widespread use, there are no data on initiation of thyroid hormone use in older people. We report the prevalence of thyroid hormone use and predictors of thyroid hormone initiation in a population of older men and women.
Methods.
Thyroid hormone medication data were collected annually from 1989 to 2006 in community-dwelling individuals aged 65 years and older enrolled in the Cardiovascular Health Study (N = 5,888). Associations of age, sex, race, body mass index, education, and coronary heart disease with initiation were evaluated using discrete-time survival analysis.
Results.
In 1989–1990, 8.9% (95% confidence interval 8.1%–9.7%) of participants were taking a thyroid hormone preparation, increasing to 20.0% (95% confidence interval 8.2%–21.8%) over 16 years. The average initiation rate was 1% per year. The initiation rate was nonlinear with age, and those aged 85 years and older initiated thyroid hormone more than twice as frequently as those aged 65–69 years (hazard ratio = 2.34; 95% confidence interval 1.43–3.85). White women were more likely to initiate thyroid hormone than any other race and sex group. Higher body mass index was independently associated with higher risk for initiation (p = .002) as was greater education (p = .02) and prevalent coronary heart disease (p = .03).
Conclusions.
Thyroid hormone use is common in older people. The indications and benefits of thyroid hormone use in older individuals with the highest rate of thyroid hormone initiation—the oldest old, overweight and obese individuals, and those with coronary heart disease—should be investigated.
doi:10.1093/gerona/glr063
PMCID: PMC3143350  PMID: 21628677
Thyroid hormone; Levothyroxine; Elderly population
11.  Frailty Status and Altered Glucose-Insulin Dynamics 
Background.
We examined women in their 80s and 90s and evaluated the hypothesis that abnormalities in the dynamic response of glucose and insulin to a glucose load are associated with frailty status.
Methods.
We performed a 75 g oral glucose tolerance test in 73 community-dwelling women aged 84–95 years without known diabetes enrolled in the Women’s Health and Aging Study II. We examined the association of frailty status (nonfrail, prefrail, or frail) with oral glucose tolerance test glucose and insulin levels at 0, 30, 60, 120, and 180 minutes using multiple linear regression models.
Results.
Using American Diabetes Association criteria, only 27% of older women had normal glucose status, 48% had prediabetes, and 25% had undiagnosed diabetes. Fasting glucose, fasting insulin, homeostasis model of assessment-insulin resistance, and Matsuda index were similar by frailty status, adjusting for age and body mass index. Conversely, mean oral glucose tolerance test glucose levels were higher at 60 minutes (44.6 ± 18.1 mg/dL higher) and 120 minutes (67.1 ± 23.5 mg/dL higher) and to a lesser extent at 180 minutes (44.3 ± 22.5 mg/dL higher) in frail versus nonfrail women as was integrated glucose area after adjustment. Mean 120-minute insulin level was also higher in frail versus nonfrail women (45.7 ± 22.4 μU/mL higher). Overall, glucose and insulin responses were more exaggerated and prolonged in frail versus nonfrail or prefrail women.
Conclusions.
Our data demonstrate dysregulation in response to glucose challenge as a component of physiologic vulnerability associated with frailty in old–old women. Future studies should examine the timing of abnormal glucose–insulin dynamics with respect to the pathogenesis of frailty.
doi:10.1093/gerona/glr141
PMCID: PMC3670159  PMID: 21873592
Glucose; Insulin; Dynamics; Elderly; Frailty
12.  The Effects of Metformin and Leuprolide Acetate on Insulin Resistance and Testosterone Levels in Non-Diabetic Postmenopausal Women: A Randomized, Placebo-Controlled Trial 
Fertility and sterility  2010;94(6):2161-2166.
Objective
To determine whether insulin sensitizers lower androgen levels and whether androgen suppression improves insulin resistance in non-diabetic postmenopausal women.
Design
Randomized, double-blind, placebo-controlled study
Setting
Clinical and Translational Research Center of a university hospital
Patients
Thirty-five postmenopausal women aged 50-79 yr with insulin resistance and higher testosterone levels
Interventions
Subjects were randomized to metformin plus leuprolide placebo (LP), leuprolide plus metformin placebo (MP), or LP plus MP in a 1:1:1 fashion over a 12 week period.
Main Outcome Measures
Insulin sensitivity (M) assessed by euglycemic-hyperinsulinemic clamp and free testosterone by equilibrium dialysis.
Results
In those randomized to metformin, free testosterone decreased by 19% (p=0.02) compared to placebo, along with an expected improvement in M. Total testosterone also decreased significantly (p=0.001) whereas sex hormone binding globulin (SHBG) did not change. In those randomized to leuprolide, the percent change in M was not different from placebo (p=0.56), despite a 48% relative decrease in free testosterone levels (p<0.001).
Conclusions
These data are the first to establish a causal link between insulin resistance and testosterone in postmenopausal women. They confirm that treatment of insulin resistance decreases testosterone production in this population and demonstrate that pharmacologic lowering of testosterone does not affect insulin resistance.
doi:10.1016/j.fertnstert.2010.01.064
PMCID: PMC2891358  PMID: 20226444
Testosterone; insulin resistance; polycystic ovary syndrome; metabolic syndrome; aging; elderly; women
13.  Relationship of Low-Circulating “Anti-Aging” Klotho Hormone with Disability in Activities of Daily Living among Older Community-Dwelling Adults 
Rejuvenation Research  2012;15(3):295-301.
Abstract
The aging suppressor gene klotho encodes a single-pass transmembrane protein klotho that in mice is known to extend life span when overexpressed and to resemble accelerated aging, with skeletal muscle atrophy and decreased bone mineral density, when expression is disrupted. We sought to examine the relationship between plasma klotho and disability in activities of daily living (ADL) in older community-dwelling adults. In a cross-sectional study, plasma klotho was measured in a population-based sample of 802 adults, ≥65 years, who participated in the “Invecchiare in Chianti” (Aging in the Chianti Area) (InCHIANTI) study in Tuscany, Italy. The overall proportion of adults with ADL disability was 11.9%. Mean (standard deviation) klotho concentrations were 689 (238) pg/mL. From the lowest to the highest tertile of plasma klotho, 16.1%, 9.7%, and 5.6% of participants, respectively, had ADL disability (p=0.0004). Plasma klotho, per 1 standard deviation increase, was associated with ADL disability (odds ratio=0.57, 95% confidence interval 0.35–0.93, p=0.02) in a multivariate logistic regression model adjusting for age, education, cognition, physical activity, physical performance, total cholesterol, alcohol and tobacco use, and chronic diseases. Low plasma klotho concentrations were independently associated with ADL disability among older community-dwelling men and women.
doi:10.1089/rej.2011.1268
PMCID: PMC3388499  PMID: 22530731
14.  Serum 25-Hydroxyvitamin D and Pulmonary Function in Older Disabled Community-Dwelling Women 
Background.
Recent studies have expanded the functions of vitamin D to a possible role in pulmonary function. Our objective was to examine the relationship between serum 25-hydroxyvitamin D (25[OH]D), serum parathyroid hormone, and pulmonary function in older women.
Methods.
We examined the relationship of serum 25(OH)D and parathyroid hormone with pulmonary function (forced expiratory volume in one second [FEV1], forced vital capacity [FVC], and FEV1/FVC ratio) in a cross-sectional study of 646 moderately to severely disabled women, 65 years or more, living in the community in Baltimore, Maryland, who participated in the Women’s Health and Aging Study I.
Results.
Overall, median (25th, 75th percentile) serum 25-hydroxyvitamin D concentrations were 19.9 (14.7, 26.7) ng/mL. Serum 25(OH)D was positively associated with FEV1 (p = .03), FVC (p = .18), and FEV1/FVC (p = .04) in multivariable linear regression models adjusting for age, race, education, smoking, height, physical activity, cognition, interleukin-6, chronic diseases, and other potential confounders. In the same models, serum parathyroid hormone was not significantly associated with FEV1, FVC, or FEV1/FVC.
Conclusions.
These findings support the idea that vitamin D deficiency is independently associated with poor pulmonary function in older disabled women.
doi:10.1093/gerona/glr213
PMCID: PMC3732158  PMID: 22156439
Aging; Lung function; Parathyroid hormone; Vitamin D; Women
15.  Trajectories of Dehydroepiandrosterone Sulfate Predict Mortality in Older Adults: The Cardiovascular Health Study 
Background
Dehydroepiandrosterone sulfate (DHEAS) has been proposed as an antiaging hormone, but its importance is unclear. Assessment of an individual’s ability to maintain a DHEAS set point, through examination of multiple DHEAS levels over time, may provide insight into biologic aging.
Methods
Using Cox proportional hazard models, we examined the relationship between DHEAS trajectory patterns and all-cause death in 950 individuals aged ≥65 years who were enrolled in the Cardiovascular Health Study and had DHEAS levels measured at three to six time points.
Results
Overall, there was a slight decline in DHEAS levels over time (−0.013 μg/mL/y). Three trajectory components were examined: slope, variability, and baseline DHEAS. When examined individually, a steep decline or extreme variability in DHEAS levels was associated with higher mortality (p < .001 for each), whereas baseline DHEAS level was not. In adjusted models including all three components, steep decline (hazard ratio [HR] 1.75, confidence interval [CI] 1.32–2.33) and extreme variability (HR 1.89, CI 1.47–2.43) remained significant predictors of mortality, whereas baseline DHEAS level remained unpredictive of mortality (HR 0.97 per standard deviation, CI 0.88–1.07). The effect of trajectory pattern was more pronounced in men than in women. Individuals with both a steep decline and extreme variability in DHEAS levels had a significantly higher death rate than those with neither pattern (141 vs 48 deaths per 1,000 person-years, p < .001).
Conclusions
Our data show significant heterogeneity in the individual trajectories of DHEAS levels and suggest that these trajectories provide important biologic information about the rate of aging, whereas the DHEAS level itself does not.
doi:10.1093/gerona/glp129
PMCID: PMC2773814  PMID: 19713299
DHEA; DHEAS; Mortality; Aging; Elderly
16.  A Meta-Analysis of Thyroid-Related Traits Reveals Novel Loci and Gender-Specific Differences in the Regulation of Thyroid Function 
Porcu, Eleonora | Medici, Marco | Pistis, Giorgio | Volpato, Claudia B. | Wilson, Scott G. | Cappola, Anne R. | Bos, Steffan D. | Deelen, Joris | den Heijer, Martin | Freathy, Rachel M. | Lahti, Jari | Liu, Chunyu | Lopez, Lorna M. | Nolte, Ilja M. | O'Connell, Jeffrey R. | Tanaka, Toshiko | Trompet, Stella | Arnold, Alice | Bandinelli, Stefania | Beekman, Marian | Böhringer, Stefan | Brown, Suzanne J. | Buckley, Brendan M. | Camaschella, Clara | de Craen, Anton J. M. | Davies, Gail | de Visser, Marieke C. H. | Ford, Ian | Forsen, Tom | Frayling, Timothy M. | Fugazzola, Laura | Gögele, Martin | Hattersley, Andrew T. | Hermus, Ad R. | Hofman, Albert | Houwing-Duistermaat, Jeanine J. | Jensen, Richard A. | Kajantie, Eero | Kloppenburg, Margreet | Lim, Ee M. | Masciullo, Corrado | Mariotti, Stefano | Minelli, Cosetta | Mitchell, Braxton D. | Nagaraja, Ramaiah | Netea-Maier, Romana T. | Palotie, Aarno | Persani, Luca | Piras, Maria G. | Psaty, Bruce M. | Räikkönen, Katri | Richards, J. Brent | Rivadeneira, Fernando | Sala, Cinzia | Sabra, Mona M. | Sattar, Naveed | Shields, Beverley M. | Soranzo, Nicole | Starr, John M. | Stott, David J. | Sweep, Fred C. G. J. | Usala, Gianluca | van der Klauw, Melanie M. | van Heemst, Diana | van Mullem, Alies | H.Vermeulen, Sita | Visser, W. Edward | Walsh, John P. | Westendorp, Rudi G. J. | Widen, Elisabeth | Zhai, Guangju | Cucca, Francesco | Deary, Ian J. | Eriksson, Johan G. | Ferrucci, Luigi | Fox, Caroline S. | Jukema, J. Wouter | Kiemeney, Lambertus A. | Pramstaller, Peter P. | Schlessinger, David | Shuldiner, Alan R. | Slagboom, Eline P. | Uitterlinden, André G. | Vaidya, Bijay | Visser, Theo J. | Wolffenbuttel, Bruce H. R. | Meulenbelt, Ingrid | Rotter, Jerome I. | Spector, Tim D. | Hicks, Andrew A. | Toniolo, Daniela | Sanna, Serena | Peeters, Robin P. | Naitza, Silvia
PLoS Genetics  2013;9(2):e1003266.
Thyroid hormone is essential for normal metabolism and development, and overt abnormalities in thyroid function lead to common endocrine disorders affecting approximately 10% of individuals over their life span. In addition, even mild alterations in thyroid function are associated with weight changes, atrial fibrillation, osteoporosis, and psychiatric disorders. To identify novel variants underlying thyroid function, we performed a large meta-analysis of genome-wide association studies for serum levels of the highly heritable thyroid function markers TSH and FT4, in up to 26,420 and 17,520 euthyroid subjects, respectively. Here we report 26 independent associations, including several novel loci for TSH (PDE10A, VEGFA, IGFBP5, NFIA, SOX9, PRDM11, FGF7, INSR, ABO, MIR1179, NRG1, MBIP, ITPK1, SASH1, GLIS3) and FT4 (LHX3, FOXE1, AADAT, NETO1/FBXO15, LPCAT2/CAPNS2). Notably, only limited overlap was detected between TSH and FT4 associated signals, in spite of the feedback regulation of their circulating levels by the hypothalamic-pituitary-thyroid axis. Five of the reported loci (PDE8B, PDE10A, MAF/LOC440389, NETO1/FBXO15, and LPCAT2/CAPNS2) show strong gender-specific differences, which offer clues for the known sexual dimorphism in thyroid function and related pathologies. Importantly, the TSH-associated loci contribute not only to variation within the normal range, but also to TSH values outside the reference range, suggesting that they may be involved in thyroid dysfunction. Overall, our findings explain, respectively, 5.64% and 2.30% of total TSH and FT4 trait variance, and they improve the current knowledge of the regulation of hypothalamic-pituitary-thyroid axis function and the consequences of genetic variation for hypo- or hyperthyroidism.
Author Summary
Levels of thyroid hormones are tightly regulated by TSH produced in the pituitary, and even mild alterations in their concentrations are strong indicators of thyroid pathologies, which are very common worldwide. To identify common genetic variants associated with the highly heritable markers of thyroid function, TSH and FT4, we conducted a meta-analysis of genome-wide association studies in 26,420 and 17,520 individuals, respectively, of European ancestry with normal thyroid function. Our analysis identified 26 independent genetic variants regulating these traits, several of which are new, and confirmed previously detected polymorphisms affecting TSH (within the PDE8B gene and near CAPZB, MAF/LOC440389, and NR3C2) and FT4 (within DIO1) levels. Gender-specific differences in the genetic effects of several variants for TSH and FT4 levels were identified at several loci, which offer clues to understand the known sexual dimorphism in thyroid function and pathology. Of particular clinical interest, we show that TSH-associated loci contribute not only to normal variation, but also to TSH values outside reference range, suggesting that they may be involved in thyroid dysfunction. Overall, our findings add to the developing landscape of the regulation of thyroid homeostasis and the consequences of genetic variation for thyroid related diseases.
doi:10.1371/journal.pgen.1003266
PMCID: PMC3567175  PMID: 23408906
17.  Multiple Hormonal Deficiencies in Anabolic Hormones Are Found in Frail Older Women: The Women's Health and Aging Studies 
Background
Alterations in anabolic hormones are theorized to contribute to aging and frailty, with most studies focusing on the relationship between individual hormones and specific age-associated diseases. We hypothesized that associations with frailty would most likely manifest in the presence of deficits in multiple anabolic hormones.
Methods
The relationships of serum levels of total IGF-1, DHEAS, and free testosterone (T) with frailty status (nonfrail, prefrail, or frail) were analyzed in 494 women aged 70–79 years enrolled in the Women's Health and Aging Studies I or II. Using multivariate polytomous regression, we calculated the odds of frailty for deficiency in each hormone (defined as the bottom quartile of the hormone) individually, as well as for a count of the hormones.
Results
For each hormone, in adjusted analyses, those with the deficiency were more likely to be frail than those without the deficiency, although this did not achieve statistical significance (IGF-1: odds ratio [OR] 1.82, confidence interval [CI] 0.81–4.08; DHEAS: OR 1.68, CI 0.77–3.69; free T: OR 2.03, CI 0.89–4.64). Compared with those with no hormonal deficiencies, those with one deficiency were not more likely to be frail (OR 1.15, CI 0.49–2.68), whereas those with two or three deficiencies had a very high likelihood of being frail (OR 2.79, CI 1.06–7.32), in adjusted models.
Conclusions
The absolute burden of anabolic hormonal deficiencies is a stronger predictor of frailty status than the type of hormonal deficiency, and the relationship is nonlinear. These analyses suggest generalized endocrine dysfunction in the frailty syndrome.
doi:10.1093/gerona/gln026
PMCID: PMC2655016  PMID: 19182229
Hormones; Aging; Elderly; Women; Frailty; IGF-1; DHEAS; Testosterone
18.  Relationship of serum fibroblast growth factor 23 with cardiovascular disease in older community-dwelling women 
Objective
Although fibroblast growth factor 23 (FGF23) has been implicated in the pathogenesis of cardiovascular disease, the relationship between FGF23 and cardiovascular disease has not been well characterized in the general population. The aim of the study was to determine whether serum FGF23 is independently associated with cardiovascular disease in older community-dwelling women.
Design and methods
A cross-sectional design was used to examine the relationship between serum FGF23 and cardiovascular disease. The subjects consisted of a population-based sample of 659 women, aged 70–79 years, who participated in the Women’s Health and Aging Studies in Baltimore, Maryland. Prevalent cardiovascular disease (coronary heart disease, stroke, congestive heart failure, peripheral artery disease) was assessed through diagnostic algorithms and physician adjudication.
Results
Of the 659 women, 185 (28.1%) had cardiovascular disease. Median (25th, 75th percentile) intact serum FGF23 was 34.6 (25.2, 46.2) pg/mL. The prevalence of cardiovascular disease in the lowest, middle, and highest tertile of serum FGF23 was 22.6%, 24.9%, and 36.7%, respectively (P = 0.002). Serum log FGF23 was associated with cardiovascular disease (Odds Ratio per 1 SD increase = 1.23, 95% Confidence Interval 1.17, 1.30; P <0.0001) in a multivariable logistic regression model, adjusting for age, race, smoking, education, body mass index, cognition, diabetes, hypertension, physical activity, total cholesterol, HDL cholesterol, and renal function.
Conclusion
Elevated serum FGF23 concentrations are independently associated with prevalent cardiovascular disease in older community-dwelling women. Further studies are needed to elucidate the potential biological mechanisms by which FGF23 may be involved in the pathogenesis of cardiovascular disease.
doi:10.1530/EJE-11-0577
PMCID: PMC3486640  PMID: 21873490
aging; cardiovascular disease; fibroblast growth factor 23; women
19.  Plasma klotho and cardiovascular disease in adults 
OBJECTIVES
To determine whether plasma klotho, a recently discovered hormone that has been implicated in atherosclerosis, is related to prevalent cardiovascular disease in adults.
DESIGN
Cross-sectional.
SETTING
Population-based sample of adults residing in Tuscany, Italy.
PARTICIPANTS
One thousand and twenty-three men and women, aged 24–102, participating in the Invecchiare in Chianti (InCHIANTI) study.
MEASUREMENTS
Anthropometric measures, plasma klotho, fasting plasma total, high-density lipoprotein (HDL) cholesterol, triglycerides, glucose, creatinine, C-reactive protein. Clinical measures: medical assessment, diabetes mellitus, hypertension, coronary heart disease, heart failure, stroke, peripheral artery disease, cancer, chronic kidney disease. Logistic regression models were used to examine the relationship between plasma klotho and prevalent cardiovascular disease.
RESULTS
Of 1023 participants, 259 (25.3%) had cardiovascular disease. Median (25th, 75th percentile) plasma klotho concentrations were 676 (530, 819) pg/mL. Plasma klotho was correlated with age (r = −0.14, P <0.0001), HDL cholesterol (r = 0.11, P = 0.0004), C-reactive protein (r = −0.10, P = 0.0008), but not systolic blood pressure, fasting plasma glucose, or renal function. Plasma klotho age-adjusted geometric means (95% Confidence Interval [C.I.]) were 626 (601, 658) in participants with cardiovascular disease and 671 (652, 692) pg/mL in those without cardiovascular disease (P = 0.0001). Adjusting for traditional cardiovascular risk factors (age, sex, smoking, total cholesterol, HDL cholesterol, systolic blood pressure, and diabetes), log plasma klotho was associated with prevalent cardiovascular disease (Odds Ratio per 1 standard deviation increase = 0.85, 95% C.I. 0.72, 0.99).
CONCLUSION
In community-dwelling adults, higher plasma klotho concentrations are independently associated with a lower likelihood of having cardiovascular disease.
doi:10.1111/j.1532-5415.2011.03558.x
PMCID: PMC3486641  PMID: 21883107
aging; atherosclerosis; cardiovascular disease; C-reactive protein; klotho
20.  DHEAS Levels and Mortality in Disabled Older Women: The Women’s Health and Aging Study I 
Background
Dehydroepiandrosterone sulfate (DHEAS) is an endogenously produced sex steroid that has been hypothesized to have anti-aging effects. Low DHEAS levels are associated with mortality in older men, but the relationship between DHEAS levels and mortality in women is not clearly defined.
Methods
The relationship between serum DHEAS level and 5-year mortality was analyzed in a cohort of 539 disabled women aged 65–100 years enrolled in the Women’s Health and Aging Study I (WHAS I). Using Cox proportional hazard models, we calculated multivariate-adjusted mortality risks by DHEAS quartiles and by DHEAS continuously, allowing for a nonlinear relationship. We also examined cause-specific mortality.
Results
We found a U-shaped relationship between DHEAS level and mortality. After adjusting for multiple covariates, women in the top and bottom DHEAS quartiles had a more than 2-fold higher 5-year mortality than did those in the middle quartiles (hazard ratio, 2.15; 95% confidence interval [CI], 1.17–3.98 for the top quartile and 2.05; 95% CI, 1.27–3.32 for the bottom quartile, each compared to the third quartile). Women with higher DHEAS levels tended to have greater cancer mortality, whereas those with lower DHEAS tended to have greater cardiovascular mortality.
Conclusion
Disabled older women with either low or high levels of DHEAS are at greater risk for death than are those with intermediate levels. More research is needed to determine if targeted dehydroepiandrosterone supplementation would provide clinical benefit to disabled older women.
PMCID: PMC2645634  PMID: 16960027
21.  Relationship of low plasma klotho with poor grip strength in older community-dwelling adults: the InCHIANTI study 
European journal of applied physiology  2011;112(4):1215-1220.
Handgrip strength is a strong indicator of total body muscle strength and is a predictor of poor outcomes in older adults. The aging suppressor gene klotho encodes a single-pass transmembrane protein that is secreted as a circulating hormone. In mice, disruption of klotho expression results in a syndrome that includes sarcopenia, atherosclerosis, osteoporosis, and shortened lifespan, and conversely, overexpression of klotho leads to a greater longevity. The objective was to determine whether plasma klotho levels are related to skeletal muscle strength in humans. We measured plasma klotho in 804 adults, ≥65 years, in the InCHIANTI study, a longitudinal population-based study of aging in Tuscany, Italy. Grip strength was positively correlated with plasma klotho at threshold <681 pg/mL. After adjusting for age, sex, education, smoking, physical activity, cognition, and chronic diseases, plasma klotho (per 1 standard deviation increase) was associated with grip strength (beta = 1.20, standard error = 0.35, P = 0.0009) in adults with plasma klotho <681 pg/mL. These results suggest that older adults with lower plasma klotho have poor skeletal muscle strength.
doi:10.1007/s00421-011-2072-3
PMCID: PMC3435096  PMID: 21769735
aging; klotho; muscle strength; sarcopenia
22.  Thyroid Status, Cardiovascular Risk, and Mortality in Older Adults: The Cardiovascular Health Study 
Context
Previous studies have suggested that subclinical abnormalities in TSH levels are associated with detrimental effects on the cardiovascular system.
Objective
To determine the relationship between baseline thyroid status and incident atrial fibrillation, incident cardiovascular disease, and mortality in older men and women not taking thyroid medication.
Design, Setting, and Patients
Participants were 3,233 US community-dwelling individuals aged 65 or over with baseline serum TSH levels who were enrolled in 1989–1990 in the Cardiovascular Health Study (CHS), a large, prospective cohort study.
Main Outcome Measures
Incident atrial fibrillation, coronary heart disease, cerebrovascular disease, cardiovascular death, and all-cause death assessed through June, 2002.
Results
Analyses are reported for four groups defined according to thyroid function test results: subclinical hyperthyroidism, euthyroidism, subclinical hypothyroidism, and overt hypothyroidism. Individuals with overt thyrotoxicosis were excluded due to small numbers. Eighty-two percent of participants were euthyroid, 15% had subclinical hypothyroidism, 1.6% were overtly hypothyroid, and 1.5% had subclinical hyperthyroidism. After exclusion of those with prevalent atrial fibrillation, individuals with subclinical hyperthyroidism had a greater incidence of atrial fibrillation compared to the euthyroid group (67 events vs. 31 events per 1,000 person-years; p<.001, and an adjusted hazard ratio [AHR] of 1.98; 95% confidence interval [CI] 1.29–3.03). No differences were seen between the subclinical hyperthyroidism group and euthyroid group for incident coronary heart disease, cerebrovascular disease, cardiovascular death, or all-cause death. Likewise, there were no differences between the subclinical hypothyroidism or overt hypothyroidism groups and the euthyroid group for cardiovascular outcomes or mortality. Specifically, individuals with subclinical hypothyroidism had an AHR of 1.07 (95% CI, 0.90–1.28) for incident coronary heart disease.
Conclusions
Our data show an association between subclinical hyperthyroidism and the development of atrial fibrillation, but do not support the hypothesis that unrecognized subclinical hyperthyroidism or subclinical hypothyroidism is associated with other cardiovascular disorders or mortality.
doi:10.1001/jama.295.9.1033
PMCID: PMC1387822  PMID: 16507804
Thyroid disease; cardiovascular disease; subclinical hyperthyroidism; subclinical hypothyroidism; cholesterol; atrial fibrillation; myocardial infarction; mortality; elderly; Cardiovascular Health Study
23.  Plasma Klotho and Mortality Risk in Older Community-Dwelling Adults 
Background.
The aging-suppressor gene klotho encodes a single-pass transmembrane protein that in mice is known to extend life span when overexpressed and resemble accelerated aging when expression is disrupted. It is not known whether there is a relationship between plasma levels of secreted klotho protein and longevity in humans.
Methods.
We measured plasma klotho in 804 adults, greater than or equal to 65 years, in the InCHIANTI study, a longitudinal population-based study of aging in Tuscany, Italy.
Results.
During 6 years of follow-up, 194 (24.1%) of the participants died. In a multivariate Cox proportional hazards model, adjusting for age, sex, education, body mass index, physical activity, total cholesterol, high-density lipoprotein cholesterol, cognition, 25-hydroxyvitamin D, parathyroid hormone, serum calcium, mean arterial pressure, and chronic diseases, participants in the lowest tertile of plasma klotho (<575 pg/mL) had an increased risk of death compared with participants in the highest tertile of plasma klotho (>763 pg/mL; hazards ratio 1.78, 95% confidence interval 1.20–2.63).
Conclusions.
In older community-dwelling adults, plasma klotho is an independent predictor of all-cause mortality. Further studies are needed to elucidate the potential biological mechanisms by which circulating klotho could affect longevity in humans.
doi:10.1093/gerona/glr058
PMCID: PMC3143348  PMID: 21474560
Aging; Klotho; Longevity; Mortality
24.  Sex Hormones Are Associated with Right Ventricular Structure and Function 
Rationale: Sex hormones have effects on the left ventricle, but hormonal influences on the right ventricle (RV) are unknown.
Objectives: We hypothesized that sex hormones would be associated with RV morphology in a large cohort free of cardiovascular disease.
Methods: Sex hormones were measured by immunoassay and RV ejection fraction (RVEF), stroke volume (RVSV), mass, end-diastolic volume, and end-systolic volume (RVESV) were measured by cardiac magnetic resonance imaging in 1,957 men and 1,738 postmenopausal women. The relationship between each hormone and RV parameter was assessed by multivariate linear regression.
Measurements and Main Results: Higher estradiol levels were associated with higher RVEF (β per 1 ln[nmol/L], 0.88; 95% confidence interval [CI], 0.32 to 1.43; P = 0.002) and lower RVESV (β per 1 ln[nmol/L], −0.87; 95% CI, −1.67 to −0.08; P = 0.03) in women using hormone therapy. In men, higher bioavailable testosterone levels were associated with higher RVSV (β per 1 ln[nmol/L], 1.97; 95% CI, 0.20 to 3.73; P = 0.03) and greater RV mass and volumes (P ≤ 0.01). Higher dehydroepiandrosterone levels were associated with higher RVSV (β per 1 ln[nmol/L], 1.37; 95% CI, 0.15 to 2.59; P = 0.03) and greater RV mass (β per 1 ln[nmol/L], 0.25; 95% CI, 0.00 to 0.49; P = 0.05) and volumes (P ≤ 0.001) in women.
Conclusions: Higher estradiol levels were associated with better RV systolic function in women using hormone therapy. Higher levels of androgens were associated with greater RV mass and volumes in both sexes.
doi:10.1164/rccm.201007-1027OC
PMCID: PMC3081282  PMID: 20889903
sex; sex hormones; right ventricle
25.  High insulin-like growth factor binding protein-1 (IGFBP-1) level predicts incident congestive heart failure in the elderly 
American Heart Journal  2008;155(6):1006-1012.
Background
Low insulin-like growth factor–1 (IGF-I) may influence the development of age-related cardiovascular diseases including congestive heart failure (CHF). Insulin-like growth factor binding protein-1 (IGFBP-1), which increases during catabolic states and inhibits anabolic IGF-I effects, is increased in CHF patients and has been associated prospectively with increased mortality among older adults and myocardial infarction survivors. We investigated the association between fasting plasma levels of IGF-I, IGFBP-1, IGFBP-3, and insulin and risk of incident CHF in the prospective Cardiovascular Health Study (CHS).
Methods
From among 5,888 65+ year-old adults in the Cardiovascular Health Study (CHS), we studied 566 incident CHF cases and 1,072 comparison subjects, after exclusion of underweight individuals (BMI < 18.5 kg/m2) and insulin users. Hazard ratios (HR) with 95% confidence intervals (CIs) for CHF were estimated after adjustment for age, race, gender, hypertension, systolic blood pressure, lipid levels, left ventricular hypertrophy, coronary disease, C-reactive protein, health status, diabetes, and BMI.
Results
High baseline IGFBP-1 level was a significant predictor of CHF, independent of established CHF risk factors and inflammation markers. The HR per SD of IGFBP-1 was 1.22 (95% CI=1.07–1.39, p < 0.01). Relative to the lowest IGFBP-1 tertile, the HR was 1.29 (95% CI=0.96–1.74, p=0.09) for the second IGFBP-1 tertile and 1.47 (95% CI=1.06–2.04; p=0.02) for the highest IGFBP-1 tertile (tertile cutpoints 19.5 and 35.8 ng/ml). Total IGF-I, IGFBP-3, or insulin levels had no association with CHF after adjustment for CHF risk factors.
Conclusions
High circulating IGFBP-1 may be a CHF risk factor among older adults.
doi:10.1016/j.ahj.2007.12.031
PMCID: PMC3286655  PMID: 18513511

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