PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-25 (35)
 

Clipboard (0)
None

Select a Filter Below

Journals
more »
Year of Publication
Document Types
1.  Temporal summation of pain as a prospective predictor of clinical pain severity in adults aged 45 years and above with knee osteoarthritis: ethnic differences 
Psychosomatic medicine  2014;76(4):302-310.
Objective
Enhanced pain facilitation is reportedly an important contributor to the clinical pain experiences of individuals with knee osteoarthritis (OA). Ethnic differences in the prevalence and severity of knee OA in addition to associated pain are also well documented. Temporal summation (TS) of pain is a widely applicable quantitative sensory testing method that invokes neural mechanisms related to pain facilitatory processes. This study tested whether TS of pain, an index of pain facilitation, differentially predicts the clinical pain experiences of African Americans and non-Hispanic Whites with symptomatic knee OA.
Methods
A total of 225 study participants underwent assessment of TS of mechanical and heat pain stimuli applied to their most symptomatic knee and their ipsilateral hand (mechanical) or forearm (heat). Using telephone-based surveys, participants subsequently reported their average and worst clinical pain severity across four consecutive weeks following assessment of TS.
Results
In predicting future clinical pain, ethnicity interacted with TS of mechanical pain (but not heat pain), such that TS of mechanical pain at the knee significantly predicted greater clinical ratings of average (b = .02, p = .016) and worst (b = .02, p = .044) clinical pain for non-Hispanic Whites but not African Americans (p’s > .30).
Conclusions
These results reveal the importance of considering ethnicity when examining pain facilitation and the clinical pain of individuals with symptomatic knee OA. The results of this study are discussed in terms of ethnic differences in the predictors of clinical pain experiences among African Americans and non-Hispanic Whites with knee OA.
doi:10.1097/PSY.0000000000000058
PMCID: PMC4066647  PMID: 24804882
Pain; Knee Osteoarthritis (OA); Ethnicity; Pain Facilitation; Temporal Summation (TS)
2.  Allelic Dependent Expression of an Activating Fc receptor on B cells Enhances Humoral Immune Responses 
Science translational medicine  2013;5(216):216ra175.
B cells are pivotal regulators of acquired immune responses and recent work in both experimental murine models and humans has demonstrated that subtle changes in the regulation of B cell function can significantly alter immunological responses. The balance of negative and positive signals in maintaining an appropriate B cell activation threshold is critical in B lymphocyte immune tolerance and autoreactivity. FcγRIIb (CD32B), the only recognized Fcγ receptor on B cells, provides IgG-mediated negative modulation through a tyrosine-based inhibition motif which down-regulates B cell receptor initiated signaling. These properties make FcγRIIb a promising target for antibody-based therapy. Here we report the discovery of allele-dependent expression of the activating FcγRIIc on B cells. Identical to FcγRIIb in the extracellular domain, FcγRIIc has a tyrosine-based activation motif in its cytoplasmic domain. In both human B cells and in B cells from mice transgenic for human FcγRIIc, FcγRIIc expression counterbalances the negative feedback of FcγRIIb and enhances humoral responses to immunization in mice and to BioThrax® vaccination in a human Anthrax vaccine trial. Moreover, the FCGR2C-ORF allele is associated with the risk of development of autoimmunity in humans. FcγRIIc expression on B cells challenges the prevailing paradigm of uni-directional negative feedback by IgG immune complexes via the inhibitory FcγRIIb, is a previously unrecognized determinant in human antibody/autoantibody responses, and opens the opportunity for more precise personalized use of B cell targeted antibody-based therapy.
doi:10.1126/scitranslmed.3007097
PMCID: PMC3982386  PMID: 24353158
3.  Resource Utilization Associated with Procurement of Transplantable Organs from Donors that do not meet OPTN Eligible Death Criteria 
Transplantation  2014;97(10):1043-1048.
Background
The strategy of evaluating every donation opportunity warrants an investigation into the financial feasibility of this practice. The purpose of this investigation is to measure resource utilization required for procurement of transplantable organs in an organ procurement organization (OPO).
Methods
Donors were stratified into those that met OPTN-defined eligible death criteria (ED Donors, n=589) and those that did not (NED Donors, n=703). Variable direct costs and time utilization by OPO staff for organ procurement were measured and amortized per organ transplanted using permutation methods and statistical bootstrapping/resampling approaches.
Results
More organs per donor were procured (3.66 ± 1.2 vs. 2.34 ± 0.8, p<0.0001) and transplanted (3.51 ± 1.2 vs. 2.08 ± 0.8, p<0.0001) in ED donors compared to NED donors. The variable direct costs were significantly lower in NED donors ($29,879.4 ± 11590.1 vs. $19,019.6 ± 7599.60, p<0.0001). In contrast, the amortized variable direct costs per organ transplanted were significantly higher in the NED donors ($8,414.5 ± 138.29 vs. $9,272.04 ± 344.56, p<0.0001). ED donors where thoracic organ procurement occurred were 67% more expensive than in abdominal-only organ procurement. The total time allocated per donor was significantly shorter in NED donors (91.2 ± 44.9 hours vs. 86.8 ± 78.6, p=0.01). In contrast, the amortized time per organ transplanted was significantly longer in the NED donors (23.1 ± 0.8 hours vs. 36.9 ± 3.2, p<0.001).
Discussion
The variable direct costs and time allocated per organ transplanted is significantly higher in donors that do not meet the eligible death criteria.
doi:10.1097/01.TP.0000441093.32217.cb
PMCID: PMC4024080  PMID: 24503760
Eligible Death Donor; Non-Eligible Death Donor; Organ Procurement; Deceased Donor Organs; Variable Direct Cost; Resource Allocation
4.  Comparison of the Disease Activity Score using Erythrocyte Sedimentation Rate and C-reactive Protein in African-Americans with Rheumatoid Arthritis 
The Journal of rheumatology  2013;40(11):1812-1822.
INTRODUCTION
The Disease Activity Score based on 28 joints (DAS28) has been increasingly used in clinical practice and research studies of rheumatoid arthritis (RA). Studies have reported discordance between DAS28 based on erythrocyte sedimentation rate (ESR) versus C-reactive protein (CRP) in RA patients. However such comparison is lacking in African-Americans with RA.
METHODS
This analysis included participants from the Consortium for the Longitudinal Evaluation of African Americans with Early Rheumatoid Arthritis (CLEAR) Registry which enrolls self-declared African-Americans with RA. Using tender and swollen joint counts separate ESR-based and CRP-based DAS28 scores (DAS28-ESR3 and DAS28-CRP3) were calculated, as were DAS28-ESR4 and DAS28-CRP4, which included the patient’s assessment of disease activity. The scores were compared using paired t-test, simple agreement and kappa, correlation coefficient and Bland-Altman plots.
RESULTS
Of the 233 included participants, 85% were women, mean age at enrollment was 52.6 years, and median disease duration at enrollment was 21 months. Mean DAS28-ESR3 was significantly higher than DAS28-CRP3 (4.8 vs. 3.9; p<0.001). Similarly, mean DAS28-ESR4 was significantly higher than DAS28-CRP4 (4.7 vs. 3.9; p<0.001). ESR-based DAS28 remained higher than CRP-based DAS28 even when stratified by age, sex, and disease duration. Overall agreement was not high between DAS28-ESR3 and DAS28-CRP3 (50%) or between DAS28-ESR4 and DAS28-CRP4 (59%). DAS28-CRP3 underestimated disease activity in 47% of the participants relative to DAS28-ESR3 and DAS28-CRP4 in 40% of the participants relative to DAS28-ESR4.
CONCLUSION
There was significant discordance between the ESR-based and CRP-based DAS28 which could impact clinical treatment decisions in African-Americans with RA.
doi:10.3899/jrheum.121225
PMCID: PMC3987124  PMID: 23950187
DAS28; Rheumatoid Arthritis; African-Americans
5.  Complementary and Alternative Medicine Use in African Americans With Rheumatoid Arthritis 
Arthritis care & research  2014;66(2):180-189.
Objective.
Racial/ethnic differences with regard to complementary and alternative medicine (CAM) use have been reported in the US. However, specific details of CAM use by African Americans with rheumatoid arthritis (RA) are lacking.
Methods.
Data were collected from African Americans with RA enrolled in a multicenter registry regarding the use of CAM, including food supplements, topical applications, activities, and alternative care providers. Factors associated with CAM use by sex and disease duration were assessed using t-test, Wilcoxon’s rank sum test, chi-square test, and logistic regression analyses.
Results.
Of the 855 participants, 85% were women and mean age at enrollment was 54 years. Overall, ever using any of the CAM treatments, activities, and providers was 95%, 98%, and 51%, respectively (median of 3 for number of treatments, median of 5 for activities, and median of 1 for providers). Those with longer disease duration (>2 years) were significantly more likely (odds ratio >2.0, P < 0.05) to use raisins soaked in vodka/gin, to take fish oils, or to drink alcoholic beverages for RA treatment than those with early disease. As compared to men, women were significantly (P < 0.05) more likely to pray/attend church, write in a journal, and use biofeedback, but were less likely to smoke tobacco or topically apply household oils for treatment of RA.
Conclusion.
CAM use was highly prevalent in this cohort, even in individuals with early disease. Health care providers need to be aware of CAM use as some treatments may potentially have interactions with conventional medicines. This could be important within this cohort of African Americans, where racial disparities are known to affect access to conventional care.
doi:10.1002/acr.22148
PMCID: PMC3977347  PMID: 23983105
6.  Gene-body mass index interactions are associated with methotrexate toxicity in rheumatoid arthritis 
Annals of the rheumatic diseases  2013;73(4):785-786.
doi:10.1136/annrheumdis-2013-204263
PMCID: PMC3970399  PMID: 24291656
Gene polymorphism; methotrexate; rheumatoid arthritis
7.  Perceived racial discrimination, but not mistrust of medical researchers, predicts the heat pain tolerance of African Americans with symptomatic knee osteoarthritis 
Objective
Studies have shown that perceived racial discrimination is a significant predictor of clinical pain severity among African Americans. It remains unknown whether perceived racial discrimination also alters the nociceptive processing of painful stimuli, which, in turn, could influence clinical pain severity. This study examined associations between perceived racial discrimination and responses to noxious thermal stimuli among African Americans and non-Hispanic whites. Mistrust of medical researchers was also assessed given its potential to affect responses to the noxious stimuli.
Method
One hundred and thirty (52% African American, 48% non-Hispanic white) community-dwelling older adults with symptomatic knee osteoarthritis completed two study sessions. In session one, individuals provided demographic, socioeconomic, physical and mental health information. They completed questionnaires related to perceived lifetime frequency of racial discrimination and mistrust of medical researchers. In session two, individuals underwent a series of controlled thermal stimulation procedures to assess heat pain sensitivity, particularly heat pain tolerance.
Results
African Americans were more sensitive to heat pain and reported greater perceived racial discrimination as well as greater mistrust of medical researchers compared to non-Hispanic whites. Greater perceived racial discrimination significantly predicted lower heat pain tolerance for African Americans but not non-Hispanic whites. Mistrust of medical researchers did not significantly predict heat pain tolerance for either racial group
Conclusion
These results lend support to the idea that perceived racial discrimination may influence the clinical pain severity of African Americans via the nociceptive processing of painful stimuli.
doi:10.1037/a0031592
PMCID: PMC3943939  PMID: 24219416
8.  Do Trained Specialists Solicit Familial Authorization at Equal Frequency, Regardless of Deceased Donor Characteristics? 
Context
The Organ Donor Breakthrough collaborative recommended high-leverage changes including “Master Effective Requesting”.
Objective
The purpose of this investigation is to measure who approaches decedent families to request organ donation. Our hypothesis is that trained specialists will solicit authorization at equal frequency regardless of donor characteristics.
Methods
A retrospective analysis of an organ center donor database was performed for the years 2006 to 2009. Decedents were stratified into those that met OPTN eligible death criteria (ED donors) and those that did not (not eligible death--NED donors).
Results
Of decedents whose families were approached for authorization, 46% were ED donors and 54% were NED donors. Trained specialists solicited authorization from 76% of the total population, but were more likely to solicit authorization from ED donors than NED donors (86% vs. 68%, p<0.0001). Trained specialists were more likely to solicit authorization from donors whose cause of death were over-represented in ED donors, and donors under the age of 50. Trained specialists were more likely to obtain authorization in both ED and NED donors. Multivariable modeling demonstrated that having a trained specialist approach the decedent’s family was associated with the highest odds of obtaining authorization.
Discussion
Trained specialists approached the majority of families of decedents for authorization, but disproportionately approached fewer families of NED donors. Having a trained specialist approach the decedent family has the strongest impact on obtaining donor authorization. These data suggest that fewer resources are allocated to NED donors, which may adversely impact deceased donor organ supply.
doi:10.7182/pit2013406
PMCID: PMC3915045  PMID: 23996950
Donor Authorization; Eligible Death Donor; Race; Cause of Death; Deceased Donor Organs
9.  The association of greater dispositional optimism with less endogenous pain facilitation is indirectly transmitted through lower levels of pain catastrophizing 
Dispositional optimism has been shown to beneficially influence various experimental and clinical pain experiences. One possibility that may account for decreased pain sensitivity among individuals who report greater dispositional optimism is less use of maladaptive coping strategies like pain catastrophizing, a negative cognitive/affective response to pain. An association between dispositional optimism and conditioned pain modulation (CPM), a measure of endogenous pain inhibition, has previously been reported. However, it remains to be determined whether dispositional optimism is also associated with temporal summation (TS), a measure of endogenous pain facilitation. The current study examined whether pain catastrophizing mediated the association between dispositional optimism and TS among 140 older, community-dwelling adults with symptomatic knee osteoarthritis. Individuals completed measures of dispositional optimism and pain catastrophizing. TS was then assessed using a tailored heat pain stimulus on the forearm. Greater dispositional optimism was significantly related to lower levels of pain catastrophizing and TS. Bootstrapped confidence intervals revealed that less pain catastrophizing was a significant mediator of the relation between greater dispositional optimism and diminished TS. These findings support the primary role of personality characteristics such as dispositional optimism in the modulation of pain outcomes by abatement of endogenous pain facilitation and less use of catastrophizing.
doi:10.1016/j.jpain.2012.10.007
PMCID: PMC3592576  PMID: 23218934
Optimism; Catastrophizing; Pain Facilitation; Temporal Summation; Osteoarthritis
10.  Gene expression patterns in peripheral blood cells associated with radiographic severity in African Americans with early rheumatoid arthritis 
Rheumatology international  2012;33(1):129-137.
Gene expression profiling may be used to stratify patients by disease severity to test the hypothesis that variable disease outcome has a genetic component. In order to define unique expression signatures in African American rheumatoid arthritis (RA) patients with severe erosive disease, we undertook a gene expression study using samples of RNA from peripheral blood mononuclear cells (PBMCs). RNA from baseline PBMC samples of 96 African American RA patients with early RA (<2 years disease duration) was hybridized to cDNA probes of the Illumina Human HT-V3 expression array. Expression analyses were performed using the ca. 25,000 cDNA probes, and then expression levels were compared to the total number of erosions in radiographs of the hands and feet at baseline and 36 months. Using a false discovery rate cutoff of Q = 0.30, 1,138 genes at baseline and 680 genes at 36 months significantly correlated with total erosions. No evidence of a signal differentiating disease progression, or change in erosion scores between baseline and 36 months, was found. Further analyses demonstrated that the differential gene expression signature was localized to the patients with the most erosive disease (>10 erosions). Ingenuity Pathway Analysis demonstrated that genes with fold change greater than 1.5 implicated immune pathways such as CTLA signaling in cytotoxic T lymphocytes. These results demonstrate that CLEAR patients with early RA having the most severe erosive disease, as compared to more mild cases (<10 erosions), may be characterized by a set of differentially expressed genes that represent biological pathways with relevance to autoimmune disease.
doi:10.1007/s00296-011-2355-3
PMCID: PMC3769702  PMID: 22238028
Genome-wide gene expression; Sharp/van der Heijde; Pathway analysis; CLEAR; ABCoN
11.  Is Decedent Race an Independent Predictor of Organ Donor Consent, or Merely a Surrogate Marker of Socioeconomic Status? 
Transplantation  2012;94(8):873-878.
Background
Studies have demonstrated that African American race is a strong predictor of non-donation. However, it is often and correctly argued that African American race is a crude explanatory variable that is a surrogate marker of socioeconomic status (SES), education and access to health care. We hypothesized that when controlling for these factors, African American race would cease to be a predictor of organ donation.
Methods
A retrospective review was performed of 1292 Alabama decedents approached for organ donation between 2006 and 2009. Multivariable logistic regression models were constructed to identify the most parsimonious model that could explain the variation in the log-odds of obtaining consent.
Results
Consent for donation was obtained from 49% of the decedent's families. Household income was a predictor of organ donor consent only in Caucasians. Surprisingly, household income was not statistically different between consented and non-consented African American decedents ($25,147 vs. $26,137; p=0.90). On multivariable analysis, education, urban residence and shorter distance between the decedent residence and donor hospital were significantly associated with obtaining consent for organ donation. On univariate analysis, the odds of donor consent in Caucasians compared to African Americans was 2.76 (95% CI 2.17 – 3.57). When controlling for SES and access to healthcare variables, the odds of donor consent increased to 4.36 (95% CI 2.88 – 6.61).
Conclusions
We interpret this result to indicate that there remains unknown but important factor(s) associated with both race and obtaining organ donor consent. Further studies are required to isolate and determine whether this factor(s) is modifiable.
doi:10.1097/TP.0b013e31826604d5
PMCID: PMC3566527  PMID: 23018878
Socioeconomic Status; Organ Donation; Education; Marital Status
12.  Dietary Glycemic Load, Glycemic Index, and Carbohydrate and Risk of Breast Cancer in the Women’s Health Initiative 
Nutrition and cancer  2011;63(6):899-907.
Dietary glycemic load (GL), glycemic index (GI), and carbohydrate could be associated with breast cancer risk by influencing long-term blood glucose and insulin concentrations. We examined associations between GL, GI, and carbohydrate and incident breast cancer in 148,767 Women’s Heath Initiative (WHI) participants. Dietary variables were estimated from food frequency questionnaires administered at baseline. Self-reported breast cancers during follow-up were confirmed by medical records review. Cox proportional hazards regression modeled time to breast cancer within quintiles of GL, GI, and carbohydrate. There were 6,115 total breast cancers after a median follow-up of 8.0 yr. We observed no associations between GL, GI, or carbohydrate and total incident breast cancer, with hazard ratios and 95% confidence intervals for the highest vs. lowest quintiles of 1.08, 0.92–1.29 (P for trend = 0.27); 1.01, 0.91–1.12 (P = 0.74); and 0.95, 0.80–1.14 (P = 0.98), respectively. There was a trend toward significance for the positive association between GL and in situ cancers (1.40, 0.94–2.13; P = 0.07). Although there was no evidence of associations between GL, GI, or carbohydrate and total breast cancer risk in WHI participants, the suggestion of an association between GL and risk of in situ cancers requires further investigation.
doi:10.1080/01635581.2011.587227
PMCID: PMC3791879  PMID: 21714685
13.  How to estimate the measurement error variance associated with ancestry proportion estimates 
Statistics and its interface  2011;4(3):327-337.
To show how the variance of the measurement error (ME) associated with individual ancestry proportion estimates can be estimated, especially when the number of ancestral populations (k) is greater than 2.
We extend existing internal consistency measures to estimate the ME variance, and we compare these estimates with the ME variance estimated by use of the repeated measurement (RM) approach. Both approaches work by dividing the genotyped markers into subsets. We examine the effect of the number of subsets and of the allocation of markers to each subset on the performance of each approach. We used simulated data for all comparisons.
Independently of the value of k, the measures of internal reliability provided less biased and more precise estimates of the ME variance than did those obtained with the RM approach. Both methods tend to perform better when a large number of subsets of markers with similar sizes are considered.
Our results will facilitate the use of ME correction methods to address the ME problem in individual ancestry proportion estimates. Our method will improve the ability to control for type I error inflation and loss of power in association tests and other genomic research involving ancestry estimates.
doi:10.4310/SII.2011.v4.n3.a7
PMCID: PMC3786624  PMID: 24089627
Population stratification; admixture; type I error inflation; reliability; Cronbach’s alpha; measurement errors; measurement error variance
14.  Correlation and Clinical Utility of pp65 Antigenemia and Quantitative Polymerase Chain Reaction Assays for Detection of Cytomegalovirus in Pediatric Renal Transplant Patients 
Pediatric transplantation  2012;16(6):627-637.
Quantitative polymerase chain reaction (qPCR) and pp65 antigenemia assays are used to monitor cytomegalovirus (CMV) infection in renal transplant recipients, but correlation of assays in a pediatric population has not been evaluated. Paired CMV real-time qPCR and pp65 antigenemia tests from 882 blood samples collected from 115 pediatric renal transplant recipients were analyzed in this retrospective cohort study for strength of association and clinical correlates.
The assays correlated well in detecting infection (κ = 0.61). Higher qPCR values were demonstrated with increasing levels of antigenemia (p < 0.01). Discordant test results were associated with antiviral treatment (OR 4.33, p < 0.01) and low-level viremia, with odds of concordance increasing at higher qPCR values (OR 3.67, p < 0.01), and no discordance occurring above 8500 genomic equivalents/mL. Among discordant samples, neither test preceded the other in detecting initial infection or in returning to negative while on treatment. Only 2 cases of disease occurred during the 2-year study period.
With strong agreement in the detection of CMV infection, either qPCR or pp65 antigenemia assays can be used effectively for monitoring pediatric renal transplant patients for both detection and resolution of infection.
doi:10.1111/j.1399-3046.2012.01741.x
PMCID: PMC3461327  PMID: 22694244
Pediatrics; Kidney Transplantation; Cytomegalovirus Infections; Polymerase Chain Reaction; CMV pp65 Antigen
15.  CAFFEINE AND URINARY INCONTINENCE IN US WOMEN 
Introduction and Hypothesis
The goal of this study was to characterize associations between caffeine consumption and severity of urinary incontinence (UI) in US women. We hypothesized that moderate and high caffeine intake would be associated with UI in US women when controlling for other factors associated with UI.
Methods
US women participated in the 2005–2006 and 2007–2008 National Health and Nutrition Examination Survey (NHANES), a cross-sectional, nationally representative survey. Using the Incontinence Severity Index, UI was categorized as “any” and “moderate/severe”. Types of UI included stress, urge, mixed, and other. Food diaries were completed and average water (gm/day), total dietary moisture (gm/day), and caffeine (mg/day) intake were calculated into quartiles. Step-wise logistic regression models were constructed adjusting for: sociodemographics, chronic diseases, body mass index, self-rated health, depression, alcohol use, dietary water and moisture in take, and reproductive factors.
Results
From the 4309 non-pregnant women (aged ≥20 years) who had complete UI and dietary data, UI prevalence for any UI was 41.0% and 16.5% for moderate/severe UI, with stress UI the most common UI type (36.6%). Women consumed a mean caffeine intake of 126.7 mg/day. After adjusting for multiple factors, caffeine in take in the highest quartile (≥204 mg/day) was associated with any UI (prevalence odds ratio (POR)1.47, 95% CI 1.07, 2.01), but not moderate/severe UI (POR 1.42, 95% CI 0.98, 2.07). Type of UI (stress, urgency, mixed) was not associated with caffeine intake.
Conclusions
Caffeine intake ≥204 mg/day was associated with any UI, but not moderate/severe UI, in US women.
doi:10.1007/s00192-012-1829-5
PMCID: PMC3505252  PMID: 22699886
urinary; incontinence; caffeine; intake; women
16.  One Year Outcomes of Tension-Free Vaginal Tape (TVT) Mid-Urethral Slings in Overweight and Obese Women 
Introduction
The purpose of this study was to assess the impact of body mass index (BMI) on tension-free vaginal tape (TVT) success rates, patient satisfaction, and complications one year following surgery.
Methods
Baseline and one-year post-surgery outcomes were abstracted, including Urogenital Distress Inventory (UDI-6) scores, Incontinence Impact Questionnaire (IIQ-7) scores, and patient satisfaction ratings. Multivariable logistic and linear regression analyses were performed to examine relationships between outcomes and BMI.
Results
195 subjects with a mean age of 59.3 ±12.6 were included. There was significant improvement within each group (all p-values <0.01) in total UDI-6 and IIQ-7 scores from baseline to one year post-surgery; all groups had high patient satisfaction. No differences in improvement or complications rates were observed among the BMI cohorts (all p-values >0.05)
Conclusion
Differential counseling of overweight or obese women regarding outcomes of the TVT procedure is not supported by these results; longer follow-up is warranted.
doi:10.1007/s00192-009-0909-7
PMCID: PMC3261075  PMID: 19448965
obesity; outcomes; TVT sling; urinary incontinence
17.  A Simple Distribution-Free Algorithm for Generating Simulated High-Dimensional Correlated Data with an Autoregressive Structure 
A distribution-free method to generate high-dimensional sequences of dependent variables with an autoregressive structure is presented. The quantile or fractile correlation (i.e., the moment correlation of the quantiles) is used as measure of dependence among a set of contiguous variables. The proposed algorithm breaks the sequence in small parts and avoids having to define one large correlation matrix for the entire high-dimensional sequence of variables. Simulations based on proteomics data are presented. Results suggest that negligible or no loss of fractile correlation occurs by splitting the generation of a sequence into small parts.
doi:10.1080/03610918.2011.579368
PMCID: PMC3217303  PMID: 22102768
Distribution-free methods; Fractile correlations; High-dimensional data; Simulation
18.  Incidence and Risk Factors for Fecal Incontinence in Black and White Older Adults: A Population-Based Study 
OBJECTIVES
To determine the incidence of fecal incontinence (FI) in community-dwelling older adults and identify risk factors associated with incident FI.
DESIGN
Planned secondary analysis of a longitudinal, population-based cohort study.
SETTING
Three rural and two urban Alabama counties (in-home assessments 2000–2005).
PARTICIPANTS
Stratified random sample of 1,000 Medicare beneficiaries: 25% African-American men, 25% white men, 25% African-American women, 25% white women, aged 65 and older. Eligible participants for this analysis were continent at baseline and community-dwelling 4 years later (n =557).
MEASUREMENTS
FI was defined as any loss of control of bowels occurring during the previous year. Independent variables were sociodemographics, Charlson comorbidity counts, self-reported bowel symptoms (chronic diarrhea and constipation), depression, and body mass index (BMI). Multivariable logistic regression models were constructed using incident FI as the dependent variable.
RESULTS
The incidence rate of FI at 4 years was 17% (95% confidence interval (CI) =13.7–20.1), with 6% developing FI at least monthly (95% CI =4.0–8.3). White women were more likely to have incident FI (22%) than African-American women (13%, P =.04); no racial differences were observed in men. Controlling for age, comorbidity count, and BMI, significant independent risk factors for incident FI in women were white race, depression, chronic diarrhea, and urinary incontinence (UI). UI was the only significant risk factor for incident FI in men.
CONCLUSION
The occurrence of new FI is common in men and women aged 65 and older, with a 17% incidence rate over 4 years. FI and UI may share common pathophysiologic mechanisms and need regular assessment in older adults.
doi:10.1111/j.1532-5415.2010.02908.x
PMCID: PMC3205963  PMID: 20533967
fecal incontinence; incidence; urinary incontinence; African Americans; gender; functional bowel disorders; epidemiology
19.  Factors Impacting quality of life in Women with fecal incontinence 
Diseases of the colon and rectum  2010;53(8):1148-1154.
Objective
To characterize differences in health-related quality of life among women presenting for treatment of fecal incontinence.
Methods
Among 155 women presenting for treatment of fecal incontinence in a specialty clinic, validated questionnaires measured impact on quality of life (Modified Manchester Health Questionnaire) and severity (the Fecal Incontinence Severity Index). Bowel symptoms, including frequency, urgency, and stool consistency, were ascertained. Co-morbid diseases were self-reported. Linear regression models were constructed from significant univariate variables to examine differences seen in quality of life scores.
Results
Average age was 58.7 ± 11.5 with no differences found in quality of life scores according to race, body mass index, or number of vaginal deliveries (p > 0.05). Younger age, increased urinary incontinence symptoms, prior cholecystectomy, prior hysterectomy, and severity of bowel symptoms correlated with a negative impact on quality of life in univariate analysis (p <0.05). Average severity scores were 30.5 ± 13.7 with moderate correlation seen with increasing severity and quality of life scores (R2= 0.60). After controlling for severity, women had increased quality of life scores with more bowel urgency (15 points, 95% CI 8.1, 21.2), harder stool consistency (10 points, 95% CI 3.8, 16.3), and prior hysterectomy (9 points, 95% CI 2.7, 15.4).
Conclusion
Bowel symptoms and having a prior hysterectomy had the greatest negative impact on quality of life in women seeking treatment for fecal incontinence. Targeting individualized treatments to improve bowel symptoms may improve quality of life for women with fecal incontinence.
doi:10.1007/DCR.0b013e3181d5da6c
PMCID: PMC2906823  PMID: 20628278
fecal incontinence; women; quality of life; urinary incontinence; bowel symptoms
20.  Generalized Bone Loss as a Predictor of 3-Year Radiographic Damage in African American Patients with Recent-Onset Rheumatoid Arthritis 
Arthritis and rheumatism  2010;62(8):2219-2226.
Objective
To examine the association between baseline bone mineral density (BMD) and radiographic damage at 3-year disease duration in a longitudinal cohort of African Americans (AAs) with recent-onset RA.
Methods
Participants (n=141) included AAs with < 2 years of disease duration. All patients underwent baseline BMD measurement (femoral neck and/or lumbar spine) using DXA. T-scores were calculated using AAs normative data. Patients were categorized as having osteopenia/osteoporosis (T score ≤ −1) or healthy. Hand/wrist radiographs, obtained at baseline and at 3-year disease duration, were scored using modified Sharp/van der Heijde method. The association between baseline BMD and total radiographic score at 3-year disease duration was examined using multivariable negative binomial regression.
Results
At baseline, the mean age and disease duration were 52.4 years and 14.8 months respectively (85.1% women). Average total radiographic scores at baseline and 3-year disease duration were 2.4 and 5.7. In the final reduced multivariable model adjusting for age, gender, anti-cyclic citrullinated peptide antibody positivity, and the presence of radiographic damage at baseline, the total radiographic score at 3-years of disease duration in patients with osteopenia/osteoporosis at the femoral neck was twice that in patients with healthy bone density and the difference was statistically significant (p=0.0084). No association between lumbar spine osteopenia/osteoporosis and radiographic score was found.
Conclusion
These findings suggest that reduced generalized BMD may be a predictor of future radiographic damage and support the hypothesis that radiographic damage and reduced generalized BMD in RA patients may share a common pathogenic mechanism.
doi:10.1002/art.27510
PMCID: PMC2922001  PMID: 20506234
21.  Capitalizing on admixture in genome-wide association studies: a two-stage testing procedure and application to height in African-Americans 
Frontiers in genetics  2011;2:00011.
As genome-wide association studies expand beyond populations of European ancestry, the role of admixture will become increasingly important in the continued discovery and fine-mapping of variation influencing complex traits. Although admixture is commonly viewed as a confounding influence in association studies, approaches such as admixture mapping have demonstrated its ability to highlight disease susceptibility regions of the genome. In this study, we illustrate a powerful two-stage testing strategy designed to uncover trait-associated single nucleotide polymorphisms in the presence of ancestral allele frequency differentiation. In the first stage, we conduct an association scan by using predicted genotypic values based on regional admixture estimates. We then select a subset of promising markers for inclusion in a second-stage analysis, where association is tested between the observed genotype and the phenotype conditional on the predicted genotype. We prove that, under the null hypothesis, the test statistics used in each stage are orthogonal and asymptotically independent. Using simulated data designed to mimic African-American populations in the case of a quantitative trait, we show that our two-stage procedure maintains appropriate control of the family wise error rate and has higher power under realistic effect sizes than the one-stage testing procedure in which all markers are tested for association simultaneously with control of admixture. We apply the proposed procedure to a study of height in 201 African-Americans genotyped at 108 ancestry informative markers. The two-stage procedure identified two statistically significant markers rs1985080 (PTHB1/BBS9) and rs952718 (ABCA12). PTHB1/BBS9 is downregulated by parathyroid hormone in osteoblastic cells and is thought to be involved in parathyroid hormone action in bones and may play a role in height. ABCA12 is a member of the superfamily of ATP-binding cassette transporters and its potential involvement in height is unclear.
doi:10.3389/fgene.2011.00011
PMCID: PMC3132882  PMID: 21754915
two-stage; structured association testing; admixture mapping; regional admixture estimate; genome-wide association studies
22.  Association of glycemic load with cardiovascular disease risk factors: the Women's Health Initiative Observational Study 
Objective
Associations between dietary glycemic load (GL) and cardiovascular disease (CVD) risk factors, including plasma lipoprotein/lipid levels, blood pressure (BP), and glucose metabolism factors, in the Women's Health Initiative Observational Study were examined.
Methods
A random sample of 878 Observational Study participants (postmenopausal women age 50 to 79 years) with baseline blood measures (647 White, 104 Black, 127 Hispanic) was included. Dietary GL was estimated from baseline food frequency questionnaires, which assessed dietary intake over the previous three months. At the baseline visit, participants completed demographic and health habit questionnaires, fasting blood samples were collected, anthropometric measurements were completed, and BP was assessed.
Results
In all participants combined, GL was inversely associated with high-density lipoprotein (HDL) cholesterol (P for trend = 0.004) and positively associated with log10-transformed triglycerides (P = 0.008). While there were no statistically significant interactions of race/ethnicity with associations between GL and CVD risk factors, stratified results were suggestive, showing that GL was positively associated with total cholesterol (P = 0.018) and low-density lipoprotein (LDL) cholesterol (P = 0.038) in Hispanics. In Whites, there was a trend of reduced HDL cholesterol with higher GL (P = 0.003), while GL was positively associated with log10-transformed triglycerides (P = 0.015). Associations between GL and HDL cholesterol and GL and triglycerides also varied by BMI, although the interactions were not statistically significant.
Conclusions
Among these generally healthy postmenopausal women, GL was associated with HDL cholesterol and triglycerides. Suggestive effects of race/ethnicity and BMI on these associations need to be confirmed in larger studies.
doi:10.1016/j.nut.2009.08.014
PMCID: PMC2866821  PMID: 20053533
Glycemic load; Glycemic index; Carbohydrate; Cardiovascular disease; Women's Health Initiative
23.  Capitalizing on Admixture in Genome-Wide Association Studies: A Two-Stage Testing Procedure and Application to Height in African-Americans 
As genome-wide association studies expand beyond populations of European ancestry, the role of admixture will become increasingly important in the continued discovery and fine-mapping of variation influencing complex traits. Although admixture is commonly viewed as a confounding influence in association studies, approaches such as admixture mapping have demonstrated its ability to highlight disease susceptibility regions of the genome. In this study, we illustrate a powerful two-stage testing strategy designed to uncover trait-associated single nucleotide polymorphisms in the presence of ancestral allele frequency differentiation. In the first stage, we conduct an association scan by using predicted genotypic values based on regional admixture estimates. We then select a subset of promising markers for inclusion in a second-stage analysis, where association is tested between the observed genotype and the phenotype conditional on the predicted genotype. We prove that, under the null hypothesis, the test statistics used in each stage are orthogonal and asymptotically independent. Using simulated data designed to mimic African-American populations in the case of a quantitative trait, we show that our two-stage procedure maintains appropriate control of the family wise error rate and has higher power under realistic effect sizes than the one-stage testing procedure in which all markers are tested for association simultaneously with control of admixture. We apply the proposed procedure to a study of height in 201 African-Americans genotyped at 108 ancestry informative markers. The two-stage procedure identified two statistically significant markers rs1985080 (PTHB1/BBS9) and rs952718 (ABCA12). PTHB1/BBS9 is downregulated by parathyroid hormone in osteoblastic cells and is thought to be involved in parathyroid hormone action in bones and may play a role in height. ABCA12 is a member of the superfamily of ATP binding cassette transporters and its potential involvement in height is unclear.
doi:10.3389/fgene.2011.00011
PMCID: PMC3132882  PMID: 21754915
two-stage; structured association testing; admixture mapping; regional admixture estimate; genome-wide association studies
24.  Comparing self-reported ethnicity to genetic background measures in the context of the Multi-Ethnic Study of Atherosclerosis (MESA) 
BMC Genetics  2011;12:28.
Background
Questions remain regarding the utility of self-reported ethnicity (SRE) in genetic and epidemiologic research. It is not clear whether conditioning on SRE provides adequate protection from inflated type I error rates due to population stratification and admixture. We address this question using data obtained from the Multi-Ethnic Study of Atherosclerosis (MESA), which enrolled individuals from 4 self-reported ethnic groups. We compare the agreement between SRE and genetic based measures of ancestry (GBMA), and conduct simulation studies based on observed MESA data to evaluate the performance of each measure under various conditions.
Results
Four clusters are identified using 96 ancestry informative markers. Three of these clusters are well delineated, but 30% of the self-reported Hispanic-Americans are misclassified. We also found that MESA SRE provides type I error rates that are consistent with the nominal levels. More extensive simulations revealed that this finding is likely due to the multi-ethnic nature of the MESA. Finally, we describe situations where SRE may perform as well as a GBMA in controlling the effect of population stratification and admixture in association tests.
Conclusions
The performance of SRE as a control variable in genetic association tests is more nuanced than previously thought, and may have more value than it is currently credited with, especially when smaller replication studies are being considered in multi-ethnic samples.
doi:10.1186/1471-2156-12-28
PMCID: PMC3068121  PMID: 21375750
25.  POPULATION-BASED STUDY OF INCIDENCE AND PREDICTORS OF URINARY INCONTINENCE IN AFRICAN AMERICAN AND WHITE OLDER ADULTS 
The Journal of urology  2008;179(4):1449-1454.
PURPOSE
To determine incidence and predictors of incident urinary incontinence over 3 years in community-dwelling older adults.
MATERIALS & METHODS
A population-based, prospective cohort study was conducted with a random sample of Medicare beneficiaries, stratified to be 50% African American, 50% men, and 50% rural. In-home baseline assessment included standardized questionnaires and short physical performance battery. Three annual follow-up interviews were conducted by telephone. Incontinence was defined as any degree of incontinence occurring at least once a month in the past 6 months.
RESULTS
Participants were 490 women and 496 men, age 65 to 106 years (mean=75 years). Prevalence of incontinence at baseline was 41% in women and 27% in men. Three-year incidence of incontinence was 29% (84/290) in women and 24% (86/363) in men. There were no differences by race in prevalent or incident incontinence. In multivariable logistic regression models for women, significant independent baseline predictors of new incontinence included: stroke (OR 3.4, p=.011), incontinence < monthly (OR 3.3, p=.001), past or current post-menopausal estrogen (OR 2.3, p<.006), slower time to stand from a chair 5 times (OR 1.3, p<.045), and higher Geriatric Depression Scale Score (OR 1.2, p=.016). For men, significant independent baseline predictors of new incontinence included: incontinence < monthly (OR 4.2, p<.001) and lower score on the composite Physical Performance Score (OR 1.2, p<.001).
CONCLUSIONS
Prevalence of incontinence among community-dwelling older adults was high with an additional 29% of women and 24% of men reporting incident incontinence over 3 years of follow-up. Infrequent incontinence is a strong risk factor for developing at least monthly incontinence in both men and women.
doi:10.1016/j.juro.2007.11.069
PMCID: PMC2999469  PMID: 18295279
Urinary Incontinence; Epidemiology; Incidence; African Americans

Results 1-25 (35)