Bing Director of the Program in Human Biology, Stanford University (2019 - Present)
Director, Stanford Military Data Repository, Stanford University School of Medicine (2015 - Present)
Honors & Awards
Distinguished Faculty Award Winner: Distinguished Educator/Mentor, University of Chicago Biological Sciences Division (2013)
BSc, Princeton University, Biology (1992)
PhD, Stanford University, Biology (1998)
Current Research and Scholarly Interests
Our research program is focused on the physical and mental health of active-duty U.S. Army soldiers. We have developed the Stanford Military Data Repository (SMDR) in collaboration with colleagues at the Army's Office of the Surgeon General to enable large-scale cohort studies addressing disability, heat injury, musculoskeletal injuries, pregnancy outcomes, and behavioral health outcomes among soldiers.
- Introduction to Statistics for the Health Sciences
HUMBIO 88 (Win)
- Principles of Epidemiology
HUMBIO 154B (Aut)
Independent Studies (8)
- Directed Reading in Health Research and Policy
HRP 299 (Aut, Win, Spr, Sum)
- Directed Reading/Special Projects
HUMBIO 199 (Aut, Win, Spr)
- Graduate Research
HRP 399 (Aut, Spr, Sum)
HUMBIO 194 (Aut, Win)
- Human Biology Internship
HUMBIO 197 (Aut, Win)
- Human Biology Practicum
HUMBIO 191 (Aut, Win, Spr)
- Research in Human Biology
HUMBIO 193 (Aut, Win)
- Teaching of Human Biology
HUMBIO 200 (Aut)
- Directed Reading in Health Research and Policy
Prior Year Courses
- Introduction to Statistics for the Health Sciences
HUMBIO 88 (Win)
- Principles of Epidemiology
HUMBIO 154B (Aut)
- Introduction to Statistics for the Health Sciences
HUMBIO 88 (Win)
- Principles of Epidemiology
HUMBIO 154B (Aut)
- Introduction to Statistics for the Health Sciences
HUMBIO 88 (Win)
- Principles of Epidemiology, with an emphasis on women's health
HUMBIO 154B (Aut)
- Introduction to Statistics for the Health Sciences
Graduate and Fellowship Programs
Biomedical Informatics (Phd Program)
Health seeking behavior after the 2013-16 Ebola epidemic: Lassa fever as a metric of persistent changes in Kenema District, Sierra Leone.
PLoS neglected tropical diseases
2021; 15 (7): e0009576
BACKGROUND: The West African Ebola epidemic of 2013-2016 killed nearly 4,000 Sierra Leoneans and devastated health infrastructure across West Africa. Changes in health seeking behavior (HSB) during the outbreak resulted in dramatic underreporting and substantial declines in hospital presentations to public health facilities, resulting in an estimated tens of thousands of additional maternal, infant, and adult deaths per year. Sierra Leone's Kenema District, a major Ebola hotspot, is also endemic for Lassa fever (LF), another often-fatal hemorrhagic disease. Here we assess the impact of the West African Ebola epidemic on health seeking behaviors with respect to presentations to the Kenema Government Hospital (KGH) Lassa Ward, which serves as the primary health care referral center for suspected Lassa fever cases in the Eastern Province of Sierra Leone.METHODOLOGY/PRINCIPAL FINDINGS: Presentation frequencies for suspected Lassa fever presenting to KGH or one of its referral centers from 2011-2019 were analyzed to consider the potential impact of the West African Ebola epidemic on presentation patterns. There was a significant decline in suspected LF cases presenting to KGH following the epidemic, and a lower percentage of subjects were admitted to the KGH Lassa Ward following the epidemic. To assess general HSB, a questionnaire was developed and administered to 200 residents from 8 villages in Kenema District. Among 194 completed interviews, 151 (78%) of respondents stated they felt hospitals were safer post-epidemic with no significant differences noted among subjects according to religious background, age, gender, or education. However, 37 (19%) subjects reported decreased attendance at hospitals since the epidemic, which suggests that trust in the healthcare system has not fully rebounded. Cost was identified as a major deterrent to seeking healthcare.CONCLUSIONS/SIGNIFICANCE: Analysis of patient demographic data suggests that fewer individuals sought care for Lassa fever and other febrile illnesses in Kenema District after the West African Ebola epidemic. Re-establishing trust in health care services will require efforts beyond rebuilding infrastructure and require concerted efforts to rebuild the trust of local residents who may be wary of seeking healthcare post epidemic.
View details for DOI 10.1371/journal.pntd.0009576
View details for PubMedID 34260615
An investigation of sickle cell trait, body mass index, and fitness in relation to venous thromboembolism among African American adults.
Journal of thrombosis and haemostasis : JTH
BACKGROUND: The relationships of sickle cell trait (SCT), body mass index, and physical fitness to venous thromboembolism (VTE) in young adults have received little attention.OBJECTIVES: To test for associations between SCT, BMI, fitness and VTE.PATIENTS/METHODS: We conducted a retrospective cohort study of 48,316 SCT-tested, African American individuals in the US Army during 2011-14. We used Cox proportional hazards models to compute adjusted hazards of deep vein thrombosis (DVT) and pulmonary embolism (PE) associated with selected factors.RESULTS: Incidence rates of DVT and PE were 1.09 and 0.91 cases per 1000 person-years, respectively. Adjusted hazard ratios (aHRs) for DVT for men and women with SCT were 0.9 (95% confidence interval [CI]: 0.4 - 2.0; P = 0.711) and 1.51 (CI: 0.7 - 3.2; P = 0.274), respectively. aHRs for PE for SCT+ men and women were 1.1 (CI: 0.5 - 2.4; P = 0.773) and 1.2 (CI: 0.5 - 3.1; P = 0.650), respectively. Low physical fitness was associated with DVT and PE in women (DVT aHR = 3.1; CI: 1.4 - 6.5; P = 0.004; PE aHR = 4.6; CI: 2.1 - 9.9; P < 0.001) and DVT in men (aHR = 2.2; CI: 1.0 - 4.6; P = 0.048). A one BMI point increase was associated with DVT in men (aHR = 1.8; CI: 1.1 - 2.8; P = 0.017).CONCLUSIONS: We found no evidence of increased VTE risk associated with SCT in this population. However, lower fitness levels and BMI increases were so associated.
View details for DOI 10.1111/jth.15422
View details for PubMedID 34105875
Military Occupational Disability Risk Surveillance: A Retrospective Cohort Study of Modifiable Risk Factors.
INTRODUCTION: Occupational disability among military service members is an important target for preventive screening. The specific aim of this study was to quantify disability risk levels among soldiers with selected risk factors (body mass index extremes, poor or absent physical fitness scores, and tobacco and opioid use) and combinations thereof, suggesting priorities for preventive actions.MATERIALS AND METHODS: This was a retrospective cohort study of 607,006 active-duty soldiers who served in the U.S. Army during 2011-2014. Official medical and administrative data were combined to produce a person-month-based panel dataset with identifiers removed. The subjects were observed longitudinally for incident disability (termed medical nonreadiness) during 1,305,618 person-years at risk. We employed Weibull parametric survival regression models to determine the adjusted medical nonreadiness hazard for selected variables. We then computed individual adjusted risk scores and the population proportions affected by risk factors and combinations thereof in postregression analyses. The project was approved by the Stanford University's Institutional Review Board and underwent secondary review by the Human Research Protections Office of the Defense Health Agency.RESULTS: During the observed time, 81,571 (13.4%) of subjects were found medically not ready. High or low body mass index, low or missing physical fitness test scores, tobacco use, and the highest levels of opioid use were each associated with increased adjusted hazards of medical nonreadiness. The hazards increased substantially when multiple risk factors were present, albeit while affecting reduced population proportions.CONCLUSIONS: We identified marked disability hazard increases, especially in association with opioid use and high body mass index. These factors, in addition to tobacco use and low physical fitness, are potential early prevention targets for clinicians who screen military service members.
View details for DOI 10.1093/milmed/usaa175
View details for PubMedID 32779704
Stressful Life Changes and Their Relationship to Nutrition-Related Health Outcomes Among US Army Soldiers.
The journal of primary prevention
Stressful life changes may tax people's adaptive capacity. We sought to determine if and when experiences of stressful life changes were associated with increased odds of adverse nutrition-related health outcomes among US Army soldiers relative to those who did not experience the same stressful life change. An additional aim was to determine which stressful life changes had the greatest association with these outcomes and if there were gender differences in the magnitude of the associations. Stressful life changes studied included: changes in marital status, combat deployment or return from deployment, relocation, adding a child, change in rank, change in occupation, and development of a physical limitation to duty. Using longitudinal data from the Stanford Military Data Repository, which represents all active-duty soldiers aged 17-62 between 2011 and 2014 (n=827,126), we employed an event history analysis to examine associations between stressful life changes and a subsequent diagnosis of hyperlipidemia, substantial weight gain, and weight-related separation from the Army. Marriage was associated with an increase in the odds of substantial weight gain 3months later for both men and women. Developing a physical duty limitation was associated with an increase in the odds of a hyperlipidemia diagnosis 2months later for both men and women, as was substantial weight gain 2months later. Stressful life changes were also associated with increased odds of nutrition-related health outcomes, although we found gender differences in the magnitude of the associations. Findings could be used to mitigate the effects of stress on health by health professionals.
View details for DOI 10.1007/s10935-020-00583-3
View details for PubMedID 32124157
INCIDENCE OF PELVIC FLOOR DISORDERS IN US ARMY FEMALE SOLDIERS.
To determine the incidence of pelvic floor disorders (PFD) among active-duty US Army female soldiers.We studied 102,015 women for incident PFD using the Stanford Military Data Repository, which comprises medical, demographic and service-related information on all soldiers on active duty in the US Army during 2011-14. Cox proportional hazards estimated adjusted associations with PFD diagnoses. In the adjusted models, military-specific characteristics and fitness were evaluated alongside known PFD predictors.Among 102,015 subjects at risk there was a cumulative incidence of 6.4% over a mean of 27 months (median 29, range 1-42). In adjusted models, obese soldiers were more likely to have a PFD compared to those of normal weight (HR 1.23, CI 1.14-1.34, p<0.001) and those with recent weight gain were more likely to have a PFD compared to those without (HR 1.32, CI 1.24-1.40, p<0.05). Women with the lowest physical fitness scores were more likely to have a PFD (HR 1.14, CI 1.04-1.25) compared to those with the highest scores.Over a median follow-up time of 29 months, 1 in 15 women in this active-duty cohort was diagnosed with a PFD. Optimizing risk factors including BMI and physical fitness may benefit the pelvic health of female soldiers, independent of age, children, and years of service.
View details for DOI 10.1016/j.urology.2020.05.085
View details for PubMedID 32650018
- Gender differences in the associations of body mass index, physical fitness and tobacco use with lower extremity musculoskeletal injuries among new US Army soldiers INJURY PREVENTION 2019; 25 (4): 295–300
Association of Nonsteroidal Anti-inflammatory Drug Prescriptions With Kidney Disease Among Active Young and Middle-aged Adults.
JAMA network open
2019; 2 (2): e187896
Importance: Concern about the renal effects of nonsteroidand al anti-inflammatory drugs (NSAIDs) among young, healthy adults has been limited, but more attention may be warranted given the prevalent use of these agents.Objective: To test for associations between dispensed NSAIDs and incident acute kidney injury and chronic kidney disease while controlling for other risk factors.Design, Setting, and Participants: This retrospective, longitudinal cohort study used deidentified medical and administrative data on 764 228 active-duty US Army soldiers serving between January 1, 2011, and December 31, 2014. Analysis was conducted from August 1 to November 30, 2018. All individuals new to Army service were included in the analysis. Persons already serving in January 2011 were required to have at least 7 months of observable time to eliminate those with kidney disease histories.Exposures: Mean total defined daily doses of prescribed NSAIDs dispensed per month in the prior 6 months.Main Outcomes and Measures: Incident outcomes were defined by diagnoses documented in health records and a military-specific digital system.Results: Among the 764 228 participants (655 392 [85.8%] men; mean [SD] age, 28.6 [7.9] years; median age, 27.0 years [interquartile range, 22.0-33.0 years]), 502 527 (65.8%) were not dispensed prescription NSAIDs in the prior 6 months, 137 108 (17.9%) were dispensed 1 to 7 mean total defined daily doses per month, and 124 594 (16.3%) received more than 7 defined daily doses per month. There were 2356 acute kidney injury outcomes (0.3% of participants) and 1634 chronic kidney disease outcomes (0.2%) observed. Compared with participants who received no medication, the highest exposure level was associated with significantly higher adjusted hazard ratios (aHRs) for acute kidney injury (aHR, 1.2; 95% CI, 1.1-1.4) and chronic kidney disease (aHR, 1.2; 95% CI, 1.0-1.3), with annual outcome excesses per 100 000 exposed individuals totaling 17.6 cases for acute kidney injury and 30.0 cases for chronic kidney disease.Conclusions and Relevance: Modest but statistically significant associations were noted between the highest observed doses of NSAID exposure and incident kidney problems among active young and middle-aged adults.
View details for PubMedID 30768191
Trajectories of body mass index among active-duty U.S. Army soldiers, 2011-2014.
Preventive medicine reports
2019; 14: 100818
Establishing the shape and determinants of trajectories of body mass index (BMI) among Soldiers is critical given the importance of weight management to military service requirements. To establish the shape and determinants of BMI trajectories among Soldiers, we aimed to (1) model the overall BMI trajectory of Soldiers, (2) find the most common trajectory groups among Soldiers, (3) investigate the relationship between BMI trajectories and sociodemographic and military-specific characteristics, and (4) determine if there were Soldiers with large fluctuations in BMI. The study population included all US Army Soldiers on active-duty between 2011 and 2014 who were age 17-62 (n = 827,126). With longitudinal data from the Stanford Military Data Repository, we used group-based trajectory modeling to identify the BMI trajectories of Soldiers and multinomial logistic regression to estimate associations between Soldier characteristics and trajectory membership. Four distinct BMI trajectory groups were found: increasing, decreasing, constant, and inconstant. The constant, increasing, and decreasing trajectories were similar in shape and percentage between men and women. The constant trajectory had the fewest Soldiers who exceeded weight standards or had duty limitations. The increasing trajectory was associated with marriage and fewer service years. The decreasing trajectory was associated with more service years and higher educational attainment. The inconstant trajectory differed in shape between men and women. Over 6% of men and 12% of women had fluctuations in BMI indicative of weight cycling. Understanding the characteristics associated with BMI trends may assist the Army in targeting resources aimed to improve Soldier health and combat readiness.
View details for PubMedID 30805278
View details for PubMedCentralID PMC6374524
Timing and Predictors of Mild and Severe Heat Illness among New Military Enlistees.
Medicine and science in sports and exercise
PURPOSE: Heat illnesses are important and potentially fatal conditions among physically active individuals. We determined predictors of heat illness among enlistees in a large military population experiencing common physical activity patterns.METHODS: We estimated the adjusted odds of mild and severe heat illness associated with demographic, health-related, and geographic factors among active-duty, United States Army soldiers enlisting between January 2011 - December 2014 (N=238,168) using discrete-time multivariable logistic regression analyses.RESULTS: We observed 2,612 incident cases of mild heat illness (MHI) and 732 incident cases of severe heat illness (SHI) during 427,922 person-years of follow-up, with a mean and median of 21.6 and 21 months per subject. During the first six duty months, 71.3% of the MHIs and 60.2% of the SHIs occurred, peaking at month two. The odds of MHI quadrupled among those with prior SHI (OR=4.02, 95% confidence interval [CI]: 2.67 - 6.03). Body mass index (BMI) extremes increased risk substantially (ORs at BMI ≥30: for MHI, 1.41, CI 1.19 - 1.67; for SHI, 1.94, CI 1.47 - 2.56; ORs at BMI <18.5: for MHI, 1.50, CI 1.01 - 2.21; for SHI, 2.26, CI 1.16 - 4.39). Tobacco use was associated with a 55% increase (CI: 1.37 - 1.77) in MHI odds. The odds of MHI increased if taking NSAIDs, opioids or methylphenidate stimulants. Lower age and lower entry aptitude scores were associated with progressively increased MHI odds.CONCLUSION: The majority of heat illnesses occurred at the outset of service, indicating the need for focused prevention methods at the initiation of military duty. Prior heat illness, BMI extremes, medications and tobacco use represent potentially actionable risk factors to address by education, policy, and/or clinician intervention.
View details for PubMedID 29613996
Sickle Cell Trait and Heat Injury Among US Army Soldiers
AMERICAN JOURNAL OF EPIDEMIOLOGY
2018; 187 (3): 523–28
There is concern that sickle cell trait (SCT) increases risk of exertional collapse, a primary cause of which is heat injury. However, to our knowledge, no population-based studies among active individuals have addressed this, representing a critical evidence gap. We conducted a retrospective cohort study of SCT-tested African-American soldiers who were on active duty in the US Army anytime between January 2011 and December 2014. Using Cox proportional hazards models and adjusting for demographic and medical factors, we observed no significant associations between SCT and either mild heat injury (hazard ratio (HR) = 1.15, 95% confidence interval (CI): 0.84, 1.56; n = 45,999) or heat stroke (HR = 1.11, 95% CI: 0.44, 2.79; n = 46,183). Risk of mild heat injury was substantially higher among soldiers with recent prescriptions for antipsychotic agents (HR = 3.25, 95% CI: 1.33, 7.90). Risk of heat stroke was elevated among those with a prior mild heat injury (HR = 17.7, 95% CI: 8.50, 36.7) and among overweight and obese individuals (HR = 2.91 (95% CI: 1.38, 6.17) and HR = 4.04 (95% CI: 1.72, 9.45), respectively). In a setting where universal precautions are utilized to mitigate risk of exertion-related illnesses, SCT is not associated with either mild heat injury or heat stroke.
View details for PubMedID 29020197
THE PREVALENCE OF PELVIC FLOOR DISORDERS IN ACTIVE DUTY FEMALE SOLDIERS: DATA FROM THE STANFORD MILITARY DATA REPOSITORY
WILEY. 2018: S567–S568
View details for Web of Science ID 000427016100082
Deployment and Preterm Birth Among US Army Soldiers.
American journal of epidemiology
2018; 187 (4): 687–95
With increasing integration of women into combat roles in the US military, it is critical to determine whether deployment, which entails unique stressors and exposures, is associated with adverse reproductive outcomes. Few studies have examined whether deployment increases the risk of preterm birth; no studies (to our knowledge) have examined a recent cohort of servicewomen. We therefore used linked medical and administrative data from the Stanford Military Data Repository for all US Army soldiers with deliveries between 2011 and 2014 to estimate the associations of prior deployment, recency of deployment, and posttraumatic stress disorder with spontaneous preterm birth (SPB), adjusting for sociodemographic, military-service, and health-related factors. Of 12,877 deliveries, 6.1% were SPBs. The prevalence was doubled (11.7%) among soldiers who delivered within 6 months of their return from deployment. Multivariable discrete-time logistic regression models indicated that delivering within 6 months of return from deployment was strongly associated with SPB (adjusted odds ratio = 2.1, 95% confidence interval: 1.5, 2.9). Neither multiple past deployments nor posttraumatic stress disorder was significantly associated with SPB. Within this cohort, timing of pregnancy in relation to deployment was identified as a novel risk factor for SPB. Increased focus on servicewomen's pregnancy timing and predeployment access to reproductive counseling and effective contraception is warranted.
View details for PubMedID 29370332
Objective Effects of Breast Reduction Surgery on Physical Fitness.
Annals of plastic surgery
BACKGROUND: Reduction mammaplasty is known for excellent outcomes and patient satisfaction. Although patients report improvements in pain, weight loss, and exercise levels, objective data on physical fitness benefits are limited.METHODS: Using the Stanford Military Data Repository, we identified 89 US Army active duty women with at least 1 pre- and postoperative Army Physical Fitness Test (APFT) who underwent reduction mammaplasty during 2011 to 2014. We used paired t tests to compare pre- and postoperative APFT score means and raw values for push-ups, sit-ups, and the 2-mile run.RESULTS: There were 56 subjects (62.9%) who improved in total APFT scores. Total score means increased from 235.9 preoperatively to 243.4 postoperatively (P = 0.0065). Of 28 subjects with at least 2 APFT scores before and after surgery, 20 (71.4%) improved in total scores. The subgroup's mean total score increased from 237.8 to 251.3 (P = 0.0009). Comparing individual pre- and postprocedure APFTs, all subjects demonstrated a mean 3.9% (SD, 0.1) improvement in total scores, and the subpopulation of 28 improved by 6.3% (SD, 0.1). In all events, mean performance values trended toward better postoperative scores. Differences were statistically significant for the total population for the number of sit-ups (P = 0.035), and, for the subgroup of 28, differences were statistically significant for the total score (P = 0.0009), sit-ups (P = 0.0002), and push-ups (P = 0.0134).CONCLUSIONS: Reduction mammaplasty was associated with postoperative physical fitness improvements among US Army active duty women. Soldier data are useful for objectively assessing physical fitness effects of breast reduction surgery.
View details for DOI 10.1097/SAP.0000000000001167
View details for PubMedID 28650408
Long-Acting Reversible Contraceptive Placement Among Active-Duty U.S. Army Servicewomen.
Obstetrics and gynecology
2017; 129 (5): 800-809
To quantify uptake of long-acting reversible contraceptives (LARC)-intrauterine devices (IUDs) and hormonal implants-among U.S. Army active-duty female soldiers and identify characteristics associated with uptake.This retrospective cohort study used the Stanford Military Data Repository, which includes all digitally recorded health encounters for active-duty U.S. Army soldiers from 2011 to 2014. We analyzed data from women aged 18-44 years to assess rates of LARC initiation using medical billing codes. We then evaluated predictors of LARC initiation using multivariable regression.Among 114,661 servicewomen, 14.5% received a LARC method; among those, 60% received an IUD. Intrauterine device insertions decreased over the study period (38.7-35.9 insertions per 1,000 women per year, β=0.14, 95% confidence interval [CI] -0.23 to -0.05, P<.05), whereas LARC uptake increased, driven by an increase in implant insertions (20.3-35.4/1,000 women per year, β=0.41, CI 0.33-0.48, P<.001). Younger age was a positive predictor of LARC uptake: 32.4% of IUD users and 62.6% of implant users were in the youngest age category (18-22 years) compared with 9.6% and 2.0% in the oldest (36-44 years). The likelihood of uptake among the youngest women (compared with oldest) was most marked for implants (adjusted relative risk 7.12, CI 5.92-8.55; P<.001). A total of 26.2% of IUD users had one child compared with 13.2% among non-LARC users (adjusted relative risk 1.94, CI 1.85-2.04, P<.001). The majority (52.2%) of those initiating IUDs were married, which was predictive of uptake over never-married women (adjusted relative risk 1.52, CI 1.44-1.59, P<.001).Among servicewomen, we observed low but rising rates of LARC insertion, driven by increasing implant use. Unmarried and childless soldiers were less likely to initiate LARC. These findings are consistent with potential underutilization and a need for education about LARC safety and reversibility in a population facing unique consequences for unintended pregnancies.
View details for DOI 10.1097/AOG.0000000000001971
View details for PubMedID 28383371
Sickle Cell Trait, Rhabdomyolysis, and Mortality among U.S. Army Soldiers.
New England journal of medicine
2016; 375 (5): 435-442
Studies have suggested that sickle cell trait elevates the risks of exertional rhabdomyolysis and death. We conducted a study of sickle cell trait in relation to these outcomes, controlling for known risk factors for exertional rhabdomyolysis, in a large population of active persons who had undergone laboratory tests for hemoglobin AS (HbAS) and who were subject to exertional-injury precautions.We used Cox proportional-hazards models to test whether the risks of exertional rhabdomyolysis and death varied according to sickle cell trait status among 47,944 black soldiers who had undergone testing for HbAS and who were on active duty in the U.S. Army between January 2011 and December 2014. We used the Stanford Military Data Repository, which contains comprehensive medical and administrative data on all active-duty soldiers.There was no significant difference in the risk of death among soldiers with sickle cell trait, as compared with those without the trait (hazard ratio, 0.99; 95% confidence interval [CI], 0.46 to 2.13; P=0.97), but the trait was associated with a significantly higher adjusted risk of exertional rhabdomyolysis (hazard ratio, 1.54; 95% CI, 1.12 to 2.12; P=0.008). This effect was similar in magnitude to that associated with tobacco use, as compared with no use (hazard ratio, 1.54; 95% CI, 1.23 to 1.94; P<0.001), and to that associated with having a body-mass index (BMI; the weight in kilograms divided by the square of the height in meters) of 30.0 or more, as compared with a BMI of less than 25.0 (hazard ratio, 1.39; 95% CI, 1.04 to 1.86; P=0.03). The effect was less than that associated with recent use of a statin, as compared with no use (hazard ratio, 2.89; 95% CI, 1.51 to 5.55; P=0.001), or an antipsychotic agent (hazard ratio, 3.02; 95% CI, 1.34 to 6.82; P=0.008).Sickle cell trait was not associated with a higher risk of death than absence of the trait, but it was associated with a significantly higher risk of exertional rhabdomyolysis. (Funded by the National Heart, Lung, and Blood Institute and the Uniformed Services University of the Health Sciences.).
View details for DOI 10.1056/NEJMoa1516257
View details for PubMedID 27518662
View details for PubMedCentralID PMC5026312
Prediction of all-cause occupational disability among US Army soldiers
OCCUPATIONAL AND ENVIRONMENTAL MEDICINE
2016; 73 (7): 442-451
Long-term occupational disability rates associated with eventual discharges from military service have risen sharply among active-duty US Army soldiers during the last three decades, with important implications for soldier health and national security alike. To address this problem, we built predictive models for long-term, all-cause occupational disability and identified disability risk factors using a very large, multisource database on the total active-duty US Army.We conducted a cross-temporal retrospective cohort study and used mixed-effects logistic regression models to derive and validate disability risk assignments. The derivation cohort included 510 616 US Army soldiers on duty in December 2012, and the validation cohort included 483 197 soldiers on duty in December 2013.The predictive model yielded an overall c-statistic of 85.97% (95% CI 85.61% to 86.32%). Risk thresholds at the population's 75th and 95th centiles identified 80.53% and 42.08%, respectively, of the disability designations that occurred population wide during the subsequent 9 months. Frequent work excusals, high outpatient care utilisation and psychotropic medication use were the strongest independent predictors of later disability.These findings indicate that predictive models using diverse data types can successfully anticipate long-term occupational disability among US Army soldiers and could be used for disability risk screening.
View details for DOI 10.1136/oemed-2015-103436
View details for Web of Science ID 000378094300005
View details for PubMedID 27129391
Insomnia symptoms and actigraph-estimated sleep characteristics in a nationally representative sample of older adults.
journals of gerontology. Series A, Biological sciences and medical sciences
2015; 70 (2): 185-192
Reports of insomnia symptoms are common among the elderly. However, little is known about the relationship between insomnia symptoms and objective assessments of sleep in the general population of older adults. We assessed concordance between insomnia symptoms and actigraphic sleep characteristics in a nationally representative sample of older Americans.In a national probability sample of 727 adults aged 62-91 years in 2010-2011 from the National Social Life, Health, and Aging Project, respondents were asked how often they (a) feel rested when they wake up, (b) have trouble falling asleep, (c) have trouble with waking up during the night, and (d) have trouble waking up too early and not being able to fall asleep again. Responses to these questions were compared to sleep characteristics estimated from three nights of actigraphy for the same individuals. Statistical analyses were adjusted for age, gender, race and ethnicity, income, assets, and education.Feeling rested (Question (a), above) was not correlated with any actigraphy-estimated sleep characteristics. Questions (b)-(d) each had several significant correlations with the actigraphy metrics, but generally not with the specific objective sleep characteristics that each question intended to reference. In some cases, the associations were not in the expected direction.Although three of four questions about insomnia symptoms were significantly associated with objectively estimated sleep characteristics, responses seem to be general indicators of sleep quality rather than reports of specific sleep characteristics.
View details for DOI 10.1093/gerona/glu144
View details for PubMedID 25199910
Actigraphic sleep characteristics among older Americans.
2015; 1 (4): 285–92
To date, there has been no evidence about objectively measured sleep characteristics from a representative national probability sample of adults in the United States. We used actigraphy to measure the sleep characteristics of older Americans.Cross-sectional study.Sleep sub-study within Wave 2 (2010-2011) of the ongoing National Social Life, Health and Aging Project (NSHAP).Seven hundred and thirty-nine NSHAP participants aged 62-90.Not applicable.Study participants wore a wrist actigraph for 72 hours and sleep properties were compared across demographic, socioeconomic, and health-behavior related lines.Actigraph-estimated sleep time averaged 7.2 hours (SE 0.06 hr) each night; the majority of the sample (80%) slept between 5.8 and 8.6 hours/night. Average time spent awake after sleep onset (WASO) was 39 minutes (SE 1.2 min). Women had significantly more total sleep time and lower sleep fragmentation compared to men. Total sleep time increased significantly with age although sleep percentage decreased with age. Compared with White participants, African American participants had significantly more WASO (9.2 minutes, p < 0.01) and greater sleep fragmentation (2.3 percentage points, p < 0.001). WASO was significantly higher and sleep percentage significantly lower among those with less education.Both short sleepers and long sleepers - often conventionally defined as obtaining <6 and >9 hrs/night, respectively - are relatively rare among older Americans when sleep is estimated by actigraphy. Sleep quality is significantly poorer among men, African Americans, and those with less education.
View details for PubMedID 28815195
Assessment of Sleep in the National Social Life, Health, and Aging Project
JOURNALS OF GERONTOLOGY SERIES B-PSYCHOLOGICAL SCIENCES AND SOCIAL SCIENCES
2014; 69: S125-S133
The relationship of sleep to health has been an active area of research in recent years, and the National Social Life, Health, and Aging Project (NSHAP) expanded sleep data collection in Wave 2 with enhanced core questions and a novel sleep module that included an objective measure of sleep duration and quality.A randomly selected one-third of Wave 2 participants and their spouses or coresident partners were invited to participate in the sleep module. Objective sleep data were collected using wrist actigraphy, an accelerometer that records an integrated measure of motion over short epochs (15 s each). This information is stored and subsequently analyzed to determine sleep and wake periods by epoch. Individuals were instructed to wear the actiwatches for 72 hr. Several sleep parameters were derived from the accelerometer. Individuals concurrently kept a sleep diary.Sleep actigraphy data were successfully collected from 780 individuals. Many of the survey-based and the actigraph-estimated sleep parameters varied by age and gender. However, age and gender patterns often differed for sleep characteristics that were both asked and measured, such as sleep duration.The survey and actigraphy data provide different information about sleep characteristics. The opportunity to examine actigraph-estimated sleep characteristics in a nationally representative sample of older adults allows novel analyses of the associations of sleep parameters with social and health data.
View details for DOI 10.1093/geronb/gbu092
View details for Web of Science ID 000354737000012
- Exploring entrustment: housestaff autonomy and patient readmission. American journal of medicine 2014; 127 (8): 791-797
Clinical prediction of musculoskeletal-related "medically not ready" for combat duty statuses among active duty U.S. army soldiers.
2013; 178 (12): 1365-1372
No evidence-based mechanism currently exists to inform U.S. Army clinicians of soldiers at risk of being found "Medically Not Ready" for combat duty. Historically, musculoskeletal conditions represent high-frequency medical problems among Army soldiers. We explored the feasibility of using centrally archived medical and administrative data on Army soldiers in the automated prediction of musculoskeletal-related Medically Not Ready soldiers who did not deploy. We examined 56,443 active duty U.S. Army soldiers who underwent precombat medical screening during March through December 2009 and in March 2010. Musculoskeletal problems were associated with 23.0% of nonreadiness cases in the study population. We used multivariable logistic regression in derivation cohorts to compute risk coefficients and cut points. We then applied these coefficients to covariates in validation cohorts, simulating predictions 2 to 3 months before their medical screenings. The analysis yielded c statistics ranging from 83 to 90%. The predictions identified 45 to 73% and 50 to 82% of the individual male and female outcome-positive soldiers, respectively, while obtaining 83 to 95% specificity. Our findings demonstrate the potential of Army data to create evidence-based estimates of nonreadiness risk. These methods could enable earlier patient referrals and improved management, and potentially reduce medically related nondeployment.
View details for DOI 10.7205/MILMED-D-13-00182
View details for PubMedID 24306021
Sleep duration and all-cause mortality: a critical review of measurement and associations
ANNALS OF EPIDEMIOLOGY
2013; 23 (6): 361-370
Variation in sleep duration has been linked with mortality risk. The purpose of this review is to provide an updated evaluation of the literature on sleep duration and mortality, including a critical examination of sleep duration measurement and an examination of correlates of self-reported sleep duration.We conducted a systematic search of studies reporting associations between sleep duration and all-cause mortality and extracted the sleep duration measure and the measure(s) of association.We identified 42 prospective studies of sleep duration and mortality drawing on 35 distinct study populations worldwide. Unlike previous reviews, we find that the published literature does not support a consistent finding of an association between self-reported sleep duration and mortality. Most studies have employed survey measures of sleep duration, which are not highly correlated with estimates based on physiologic measures.Despite a large body of literature, it is premature to conclude, as previous reviews have, that a robust, U-shaped association between sleep duration and mortality risk exists across populations. Careful attention must be paid to measurement, response bias, confounding, and reverse causation in the interpretation of associations between sleep duration and mortality.
View details for DOI 10.1016/j.annepidem.2013.03.015
View details for Web of Science ID 000319782700010
View details for PubMedID 23622956
Loneliness Is Associated with Sleep Fragmentation in a Communal Society
2011; 34 (11): 1519-1526
Loneliness has been shown to predict poor health. One hypothesized mechanism is that lonely individuals do not sleep as well as individuals who feel more connected to others. Our goal was to test whether loneliness is associated with sleep fragmentation or sleep duration.Cross-sectional study.Members of a traditional, communal, agrarian society living in South Dakota.Ninety-five participants (mean age 39.8 years, 55% female) who were ≥ 19 years of age at the study's inception.Not applicable.We conducted interviews querying loneliness, depression, anxiety, and stress, as well as subjective sleep quality and daytime sleepiness. Study participants wore a wrist actigraph for one week to measure objective sleep properties; the two studied here were sleep fragmentation and sleep duration. Higher loneliness scores were associated with significantly higher levels of sleep fragmentation (β = 0.073, t = 2.55, P = 0.01), controlling for age, sex, body mass index, risk of sleep apnea, and negative affect (a factor comprising symptoms of depression and anxiety, and perceived stress). Loneliness was not associated with sleep duration or with either subjective sleep measure.Loneliness was a significant predictor of sleep fragmentation. Humans' social nature may partly be manifest through our dependence on feeling secure in our social environment to sleep well.
View details for DOI 10.5665/sleep.1390
View details for Web of Science ID 000296727200013
View details for PubMedID 22043123
Sex-specific genetic architecture of asthma-associated quantitative trait loci in a founder population
CURRENT ALLERGY AND ASTHMA REPORTS
2006; 6 (3): 241-246
Identifying genes that influence susceptibility to asthma-related and atopy-related phenotypes has been challenging, owing to clinical heterogeneity and a complex underlying genetic architecture that includes both gene-gene and gene-environment interactions. In this article, we report the results of genome-wide linkage and association studies of eight asthma-associated quantitative traits in the Hutterites, a founder population of European descent. Our study revealed significant sex-specific genetic architecture for at least five of these traits, and identified 13 genome-wide significant quantitative trait loci (QTL) by linkage or association that are present in only one of the sexes (nine in males, four in females).
View details for Web of Science ID 000242004400009
View details for PubMedID 16579875
Schizophrenia and cancer: an epidemiological study
BRITISH JOURNAL OF PSYCHIATRY
2005; 187: 334-338
For decades there has been interest in the possibility that people with schizophrenia might have some protection against cancer, and that, if this were so, it might hold clues about aetiological mechanisms in schizophrenia.To study cancer incidence in schizophrenia.Cohort analysis of linked hospital and death records was used to compare cancer rates in people with schizophrenia with a reference cohort.We did not find a reduced risk for cancer overall (rate ratio 0.99,95% CI 0.90-1.08) or for most individual cancers. There was, however, a significantly low rate ratio for skin cancer (0.56,95% CI 0.36-0.83).We found no evidence that schizophrenia confers protection against cancer in general. Low rates of cancer are consistent with the hypothesis that sun exposure may influence the development of schizophrenia, although other explanations are also possible.
View details for Web of Science ID 000232483500008
View details for PubMedID 16199792
Sex differences in the genetic basis of morning serum cortisol levels: Genome-wide screen identifies two novel loci specific to women
JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM
2005; 90 (8): 4747-4752
Relatively little is known about the influence of specific genes on cortisol levels, particularly morning cortisol levels.The objective of this study was to identify quantitative trait loci associated with morning serum cortisol levels.We carried out a genome screen for morning serum cortisol using linkage and association methods tailored for use in large pedigrees. We conducted these analyses both in the whole sample and partitioned by sex.This study was conducted on nine communal Hutterite farms in South Dakota.The Hutterites are a young founder population who practice a communal, farming lifestyle in the western United States and in Canada. Hutterites (n = 504, 53% female) aged 11-89 yr from a single pedigree participated in this study.The main outcome measures were markers significantly linked or associated with variation in morning serum cortisol levels.One genome-wide significant association was identified in the whole sample on 11p (D11S1981, P = 0.000092). Results of sex-partitioned analyses indicated that this association was restricted to females (females, P = 0.000084; males, P = 0.20). The 146-bp allele at this locus accounted for 7% of the variance in morning cortisol values in females, and females homozygous for the allele had an 89% increase in morning cortisol levels compared with female noncarriers. A second genome-wide significant association in females was identified on 14q (D14S74, P = 0.000091).Our results suggest that the genetic determinants of morning cortisol levels may be different for men and women and that loci on 11p and 14q influence morning cortisol levels in women.
View details for DOI 10.1210/jc.2005-0384
View details for Web of Science ID 000231068500048
View details for PubMedID 15941864
The effect of menopause on grip and pinch strength: Results from the Chicago, Illinois, site of the Study of Women's Health Across the Nation
AMERICAN JOURNAL OF EPIDEMIOLOGY
2004; 160 (5): 484-491
Women may experience a decline in physical function during menopause. Whether this decline is due to aging or to changes in hormonal status is unknown. The authors performed a longitudinal data analysis on data collected between 1996 and 2001 to determine the effects of menopausal status, age, race, and use of hormone replacement therapy (HRT) on 3-year changes in grip and pinch strength. Participants were 563 women from the Chicago, Illinois, site of the Study of Women's Health Across the Nation. According to adjusted analyses, women who became postmenopausal showed a 1.04-kg decline in grip strength (p = 0.10) and a 0.57-kg decline in pinch strength (p = 0.002) relative to women who remained premenopausal. Women who became early perimenopausal showed a 0.20-kg decline in pinch strength (p = 0.04), whereas women who transitioned to late perimenopause showed a 0.93-kg decline in grip strength (p = 0.07). Effects of menopausal status on grip and pinch strength did not vary by race. A significant HRT-by-race interaction for grip strength was found; African-American HRT users had greater grip strength during the study, whereas Caucasian HRT users did not (p = 0.05). Greater physical activity was the strongest predictor of grip and pinch strength (p < 0.0001). Results indicate that transition through menopause is associated with a decline in grip and pinch strength.
View details for DOI 10.1093/aje/kwh244
View details for Web of Science ID 000223791900010
View details for PubMedID 15321846
- The social structure, stress, and women's health CLINICAL OBSTETRICS AND GYNECOLOGY 2002; 45 (4): 1099-1118
Appendicectomy, tonsillectomy, and inflammatory bowel disease: a case-control record linkage study
1st Meeting of the International-Society-for-Equity-in-Health
BMJ PUBLISHING GROUP. 2002: 551–54
To determine whether appendicectomy and tonsillectomy are associated with ulcerative colitis (UC) or Crohn's disease (CD); and, if so, whether the associations are related to age at operation.Nested case-control studies using a longitudinal database of linked hospital and death record abstracts.Southern England.Statistical records of people diagnosed with UC, CD, or a control condition admitted to hospitals in a defined area.Appendicectomy under the age of 20 years was associated with a significantly reduced subsequent risk of UC (relative risk =0.48, 95% confidence interval 0.30 to 0.73). The association appeared strongest for appendicectomy between 10 and 14 years of age (relative risk =0.29, 95% CI 0.09 to 0.68). Appendicectomy at the age of 20 years and over was associated with an increased subsequent risk of CD (relative risk =1.92, 95% CI 1.58 to 2.32), largely confined to those people whose CD was diagnosed within a year of appendicectomy. Appendicectomy under 20 years of age, undertaken five years or more before case or control conditions, was suggestively associated with a reduced risk of CD (relative risk =0.71, 95% CI 0.47 to 1.03). Prior tonsillectomy was not associated with any increase or decrease of risk of either UC or CD.Appendicectomy is associated with a reduced risk of UC; and the association is specific to young age groups when the population risk of appendicitis is itself highest. The increased risk of CD after appendicectomy, at short time intervals between the two, is probably attributable to the misdiagnosis of CD as appendicitis.
View details for Web of Science ID 000176542100015
View details for PubMedID 12080166
- Abortion and breast cancer: a case-control record linkage study JOURNAL OF EPIDEMIOLOGY AND COMMUNITY HEALTH 2001; 55 (5): 336-337