Postpartum long-acting reversible contraceptive use among active-duty, female US Army soldiers

BACKGROUND

Postpartum use of long-acting reversible contraception has been found to be effective at increasing interpregnancy intervals, reducing unintended pregnancies, and optimizing health outcomes for mothers and babies. Among female active-duty military service members, reproductive planning may be particularly important, yet little is known about postpartum long-acting reversible contraceptive use among active-duty soldiers.

OBJECTIVE

This study aimed to (1) quantify postpartum uptake of long-acting reversible contraception among active-duty female US Army soldiers and (2) identify demographic and military-specific characteristics associated with use.

STUDY DESIGN

This retrospective cohort study used longitudinal data of all digitally recorded health encounters for active-duty US Army soldiers from 2014 to 2017. The servicewomen included in our analysis were aged 18 to 44 years with at least one delivery and a minimum of 4 months of total observed time postdelivery within the study period. We defined postpartum long-acting reversible contraception use as initiation of use within the delivery month or in the 3 calendar months following delivery and identified likely immediate postpartum initiation via the proxy of placement recorded during the same month as delivery. We then evaluated predictors of postpartum long-acting reversible contraception use with multivariable logistic regression.

RESULTS

The inclusion criteria were met by 15,843 soldiers. Of those, 3162 (19.96%) initiated the use of long-acting reversible contraception in the month of or within the 3 months following delivery. Fewer than 5% of these women used immediate postpartum long-acting reversible contraception. Among women who initiated postpartum long-acting reversible contraceptive use, 1803 (57.0%) received an intrauterine device, 1328 (42.0%) received an etonogestrel implant, and 31 received both (0.98%). Soldiers of younger age, self-reported White race, and those who were married or previously married were more likely to initiate long-acting reversible contraception in the postpartum period. Race-stratified analyses showed that self-reported White women had the highest use rates overall. When compared with these women, the adjusted odds of postpartum use among self-reported Black and Asian or Pacific Islander women were 18% and 30% lower, respectively (both P<.001). There was also a trend of decreasing postpartum use with increasing age within each race group. Differences observed between age groups and race identities could partially be attributed to differential use of permanent contraception (sterilization), which was found to be significantly more prevalent among both women aged 30 years or older and among women who identified as Black.

CONCLUSION

Among active-duty US Army servicewomen, 1 in 5 used postpartum long-acting reversible contraception, and fewer than 5% of these women used an immediate postpartum method. Within this population with universal healthcare coverage, we observed relatively low rates of use and significant differences in the uptake of effective postpartum long-acting contraceptive methods across self-reported race categories.

Physical Fitness in Relationship to Depression and Post-Traumatic Stress Disorder During Pregnancy Among U.S. Army Soldiers

Background: Depression and post-traumatic stress disorder (PTSD) are prevalent in pregnancy, especially among military members. These conditions can lead to adverse birth outcomes, yet, there's a paucity of evidence for prevention strategies. Optimizing physical fitness is one understudied potential intervention. We explored associations between prepregnancy physical fitness and antenatal depression and PTSD in soldiers. Materials and Methods: This was a retrospective cohort study of active-duty U.S. Army soldiers with live births between 2011 and 2014, identified with diagnosis codes from inpatient and outpatient care. The exposure was each individual's mean Army physical fitness score from 10 to 24 months before childbirth. The primary outcome was a composite of active depression or PTSD during pregnancy, defined using the presence of a code within 10 months before childbirth. Demographic variables were compared across four quartiles of fitness scores. Multivariable logistic regression models were conducted adjusting for potential confounders selected a priori. A stratified analysis was conducted for depression and PTSD separately. Results: Among 4,583 eligible live births, 352 (7.7%) had active depression or PTSD during pregnancy. Soldiers with the highest fitness scores (Quartile 4) were less likely to have active depression or PTSD in pregnancy (Quartile 4 vs. Quartile 1 adjusted odds ratio 0.55, 95% confidence interval 0.39-0.79). Findings were similar in stratified analyses. Conclusion: In this cohort, the odds of active depression or PTSD during pregnancy were significantly reduced among soldiers with higher prepregnancy fitness scores. Optimizing physical fitness may be a useful tool to reduce mental health burden on pregnancy.

Incidence of Ankylosing Spondylitis Among Male and Female United States Army Personnel

OBJECTIVE

Incidence rates of ankylosing spondylitis (AS) among males versus females are poorly understood. Results of prior research have been mixed, including findings of a 3:1 incidence ratio for males versus females, but with increasing AS rates among females. The objective was to estimate the incidence of AS among members of the US military.

METHODS

We estimated the incidence of AS in a retrospective cohort study of diverse, working-age US military service members during March 2014 to June 2017 (n = 728,556) who underwent clinical practice guideline-directed screening for chronic back pain. Incident AS cases were identified using diagnostic codes from electronic medical and administrative records.

RESULTS

In contrast to some prior studies, AS incidence was similar among males and females (incidence rate ratio 1.16, P = 0.23; adjusted odds ratio [OR] 0.79 [95% confidence interval (95% CI) 0.61-1.02]; P = 0.072). AS rates increased approximately monotonically with age. Consistent with prior research, the AS incidence rate was greater in the White population than in the Black population (adjusted OR 1.39 [95% CI 1.01-1.66]; P = 0.04).

CONCLUSION

In this study population, the incidence of AS was similar for the sexes. Previous observations of male predominance have typically been derived from clinic populations that are less representative of the US race/ethnicity distribution and based on disease ascertainment tools that may have identified subjects later in their disease course. Our study population also differed in being subject to organized screenings for musculoskeletal symptoms. Our findings suggest that sex may not predict AS incidence in the US population.

Service discharges among US Army personnel with selected musculoskeletal and skin conditions: a retrospective cohort study

OBJECTIVES

To determine the probability of discharge from military service among soldiers following an incident diagnosis of ankylosing spondylitis (AS), rheumatoid arthritis (RA), psoriasis or systemic lupus erythematous.

METHODS

All soldiers on active duty in the US Army between January 2014 and June 2017 were included in a retrospective cohort analysis. Termination from service was ascertained using personnel records. Diagnostic codes were used to identify incident cases of the four musculoskeletal and skin diseases and, for comparison, diabetes mellitus (DM). Time to discharge was modelled using sex stratified multivariate survival analysis.

RESULTS

The analysis included 657 417 individuals with a total of 1.2 million person-years of observation. An elevated risk of discharge was observed in association with each of the five chronic conditions studied. The increase in adjusted risk of discharge was highest among soldiers with AS (men, HR=2.5, 95% CI 2.1 to 3.0; women, HR=2.1, 95% CI 1.4 to 3.2) and with DM (men, HR=2.4, 95% CI 2.2 to 2.7; women, HR=2.2, 95% CI 1.8 to 2.5), followed by those with RA (men, HR=1.8, 95% CI 1.5 to 2.2; women, HR=1.8, 95% CI 1.4 to 2.4).

CONCLUSIONS

Military discharges are consequential for the service and the service member. The doubling in risk of discharge for those with AS or RA was comparable to that for personnel with DM. Conditions that affect the spine and peripheral joints may often be incompatible with military readiness. Nevertheless, a substantial fraction of service members with these diagnoses continued in service.

Post-Traumatic Stress Disorder Among U.S. Army Drone Operators

INTRODUCTION: Exposure to traumatic events could increase post-traumatic stress disorder (PTSD) risk among enlisted U.S. Army drone operators. Published research on PTSD risk in this population is unavailable.METHODS: We used a combined medical and administrative longitudinal dataset to examine adjusted associations between drone operator service among U.S. Army enlisted members and three PTSD indicators: whether screened via the PTSD Checklist – Civilian (PCL-C); PCL-C scores; and incident PTSD diagnoses. We compiled summary statistics for and conducted tests of differences in independent variable distributions when comparing drone operators and others. Two multivariable survival regression models and an ordinary least squares model were used to estimate adjusted associations.RESULTS: There were 1.68 million person-years of observed time in the study population (N = 678,548; drone operator N = 2856). Compared to other servicemembers, the adjusted likelihood of undergoing PTSD screening was 35% lower [95% confidence interval (CI) for the adjusted hazard ratio (aHR): 0.56–0.76]. Among subjects who took the PCL-C, scores did not differ significantly on the basis of drone operator service (adjusted change: −1.26 points; CI: −3.41–0.89). The adjusted hazard of receiving a PTSD diagnosis was 34% lower among drone operators (CI: 0.54–0.80).DISCUSSION: These findings provide reassurance that enlisted U.S. Army drone operators are not at increased risk of PTSD. Further research is needed in order to identify the mechanisms of the decreased PTSD risk observed, and whether other or longer-term mental health risks are present among those in this occupation.Nelson DA, Wilson M, Kurina LM. Post-traumatic stress disorder among U.S. Army drone operators. Aerosp Med Hum Perform. 2022; 93(7):562–570.

An investigation of sickle cell trait, body mass index, and fitness in relation to venous thromboembolism among African American adults

BACKGROUND

The relationships of sickle cell trait (SCT), body mass index (BMI), and physical fitness to venous thromboembolism (VTE) in young adults have received little attention.

OBJECTIVES

To test for associations among 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 = .711) and 1.51 (CI: 0.7-3.2; P = .274), respectively. aHRs for PE for SCT+ men and women were 1.1 (CI: 0.5-2.4; P = .773) and 1.2 (CI: 0.5-3.1; P = .650), respectively. Low physical fitness was associated with DVT and PE in women (DVT aHR =3.1; CI: 1.4-6.5; P = .004; PE aHR =4.6; CI: 2.1-9.9; P < .001) and DVT in men (aHR =2.2; CI: 1.0-4.6; P = .048). Recent weight gain of 1 or more BMI points was associated with DVT in men (aHR =1.8; CI: 1.1-2.8; P = .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.

Health seeking behavior after the 2013-16 Ebola epidemic: Lassa fever as a metric of persistent changes in Kenema District, Sierra Leone

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.

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.

Incidence of Pelvic Floor Disorders in US Army Female Soldiers

OBJECTIVE

To determine the incidence of pelvic floor disorders (PFD) among active-duty US Army female soldiers.

MATERIALS AND METHODS

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 2011-2014. Cox proportional hazards estimated adjusted associations with PFD diagnoses. In the adjusted models, military-specific characteristics and fitness were evaluated alongside known PFD predictors.

RESULTS

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 (hazard ratio [HR] 1.23, confidence interval [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.

CONCLUSION

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 body mass index and physical fitness may benefit the pelvic health of female soldiers, independent of age, children, and years of service.

Stressful Life Changes and Their Relationship to Nutrition-Related Health Outcomes Among US Army Soldiers

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 3 months later for both men and women. Developing a physical duty limitation was associated with an increase in the odds of a hyperlipidemia diagnosis 2 months later for both men and women, as was substantial weight gain 2 months 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.

Sickle cell trait and renal disease among African American U.S. Army soldiers

Sickle cell trait and certain renal disorders are disproportionately prevalent among African American individuals, so a clear understanding of their association is important. We conducted a longitudinal study using the Stanford Military Data Repository to examine sickle cell trait in relation to the incidence of acute kidney injury (AKI) and chronic kidney disease (CKD). Our study population consisted of African American U.S. Army soldiers on active duty between January 2011 and December 2014. The cumulative incidence was 0·51% for AKI (236 cases out of 45 901 soldiers) and 0·56% for CKD (255 cases out of 45 882 soldiers). Discrete time logistic regression models adjusting for demographic-, military- and healthcare-related covariates showed that sickle cell trait was associated with significantly higher adjusted odds of both AKI [odds ratio (OR): 1·74; 95% confidence interval (CI): 1·17-2·59] and CKD (OR: 2·00; 95% CI: 1·39-2·88). Elevated odds of AKI and CKD were also observed in association with prior CKD and AKI, respectively, and with obesity and prior hypertension. Individuals with sickle cell trait and their providers should be aware of the possibility of increased risk of AKI and CKD to allow for timely intervention and possible prevention.

Trajectories of body mass index among active-duty U.S. Army soldiers, 2011-2014

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.

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Four BMI trajectory groups were found: increasing, decreasing, constant, inconstant.

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The constant trajectory had the fewest Soldiers who exceeded weight standards.

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The increasing trajectory was associated with marriage and fewer service years.

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The decreasing trajectory was associated with more service years and education.

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6% of men and 12% of women had fluctuations in BMI indicative of weight cycling.

Association of Nonsteroidal Anti-inflammatory Drug Prescriptions With Kidney Disease Among Active Young and Middle-aged Adults

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.

Gender differences in limited duty time for lower limb injury

Background

Among active-duty military personnel, lower limb musculoskeletal injuries and related conditions (injuries) frequently arise as unintended consequences of physical training. These injuries are particularly common among women. The practical impact of such injuries on temporary military occupational disability has not been estimated with precision on a large scale.

Aims

To determine the proportion of service time compromised by limited duty days attributable to lower limb injuries, characterize the time affected by these limitations in terms of specific lower limb region and compare the limited duty time between male and female soldiers.

Methods

Administrative data and individual limited duty assignments (profiles) were obtained for active-duty US Army personnel who served in 2014. Lower limb injury-related profiles were used to calculate the percent of person-time requiring duty limitations by gender and body region.

Results

The study group was 568 753 soldiers of whom 14% were women. Nearly 13% of service days for active-duty US Army soldiers required limited duty for lower limb injuries during 2014. Knee injuries were responsible for 45% of those days. Within integrated military occupations, female soldiers experienced 27-57% more time on limited duty for lower limb injuries compared with men.

Conclusions

The substantial amount of limited duty for lower limb musculoskeletal injuries among soldiers highlights the need for improvement in training-related injury screening, prevention and timely treatment with particular attention to knee injuries. The excessive impact of lower limb injuries on female soldiers' occupational functions should be a surveillance priority in the current environment of expanding gender-integrated training.

Timing and Predictors of Mild and Severe Heat Illness among New Military Enlistees

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 (MHI) and severe (SHI) heat illness associated with demographic, health-related, and geographic factors among active-duty, US Army soldiers enlisting between January 2011 and December 2014 (N = 238,168) using discrete-time multivariable logistic regression analyses.

RESULTS

We observed 2612 incident cases of MHI and 732 incident cases of 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 6 duty months, 71.3% of the MHIs and 60.2% of the SHIs occurred, peaking at month 2. The odds of MHI quadrupled among those with prior SHI (odds ratio [OR], 4.02; 95% confidence interval [CI], 2.67-6.03). Body mass index (BMI) extremes increased the odds substantially (OR at BMI ≥30 kg·m: for MHI, 1.41 (CI, 1.19-1.67); for SHI, 1.94 (CI, 1.47-2.56); OR at BMI <18.5 kg·m: 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 nonsteroidal anti-inflammatory drugs, opioids, or methylphenidate stimulants. Lower age and lower entry aptitude scores were associated with progressively increased MHI odds.

CONCLUSIONS

Most 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.

Deployment and Preterm Birth Among US Army Soldiers

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.

Gender differences in the associations of body mass index, physical fitness and tobacco use with lower extremity musculoskeletal injuries among new US Army soldiers

BACKGROUND

Musculoskeletal (MSK) injuries are a leading cause of morbidity among US Army soldiers, especially among women and the newly enlisted. While extremes of body mass index (BMI), low physical fitness and tobacco use have been identified as risk factors, no prior studies have determined the combined effects of these risk factors or tested for gender differences in the associations.

METHODS

We conducted a retrospective cohort study utilising the Stanford Military Data Repository to study all enlisted soldier accessions to the US Army between January 2011 and January 2014, with follow-up through December 2014 (n=238 772). We used discrete-time logistic regression to test for associations between demographic, socioeconomic and health behaviour-related predictors and incident lower extremity injuries. We included interaction terms to test for gender differences.

RESULTS

Among men, there were greater adjusted odds of injury among underweight (OR 1.27), overweight (OR 1.14) and obese soldiers (OR 1.54) (all p<0.001) relative to normal-weight soldiers. No statistically significant differences in the odds of injury on the basis of BMI were observed for female soldiers. Physical fitness was a significantly stronger predictor of injury for female as compared with male soldiers, while the association between tobacco use and injury was stronger for men (OR 1.47) than for women (OR 1.30) (p<0.001 for both).

CONCLUSION

This is the largest known study to simultaneously assess important, modifiable musculoskeletal injury risk factors and to test for gender differences in these associations. These findings provide critical gender-related nuances for clinicians and leaders seeking to reduce the risk of these problems.

Sickle Cell Trait and Heat Injury Among US Army Soldiers

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.

Sickle Cell Trait, Rhabdomyolysis, and Mortality among U.S. Army Soldiers

BACKGROUND

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.).

Sleep duration and health among older adults: associations vary by how sleep is measured

BACKGROUND

Cohort studies have found that short and long sleep are both associated with worse outcomes, compared with intermediate sleep times. While demonstrated biological mechanisms could explain health effects for short sleep, long-sleep risk is puzzling. Most studies reporting the U shape use a single question about sleep duration, a measurement method that does not correlate highly with objectively measured sleep. We hypothesised that the U shape, especially the poor outcomes for long sleepers, may be an artefact of how sleep is measured.

METHODS

We examined the cross-sectional prevalence of fair/poor health by sleep hour categories (≤ 6, ≤ 7, ≤ 8, ≤ 9, > 9 h) in a national US sample of adults aged 62-90 that included several types of sleep measures (n = 727). Survey measures were: a single question; usual bedtimes and waking times; and a 3-day sleep log. Actigraphy measures were the sleep interval and total sleep time. Fair/poor health was regressed on sleep hour categories adjusted for demographics, with tests for both linear trend and U shape.

RESULTS

Adjusted OR of fair/poor health across sleep hour categories from the single question were 4.6, 2.2, referent (8 h), 1.8 and 6.9. There was high prevalence of fair/poor health for ≤ 6 h for all sleep measures, but the long-sleep effect was absent for sleep logs and actigraphy measures.

CONCLUSIONS

Associations between long sleep and poor health may be specific to studies measuring sleep with survey questions. As cohorts with actigraphy mature, our understanding of how sleep affects health may change.

Assessment of sleep in the National Social Life, Health, and Aging Project

OBJECTIVES

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.

METHOD

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.

RESULTS

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.

DISCUSSION

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.

Insomnia symptoms and actigraph-estimated sleep characteristics in a nationally representative sample of older adults

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Sleep duration and all-cause mortality: a critical review of measurement and associations

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Loneliness is associated with sleep fragmentation in a communal society

STUDY OBJECTIVE

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.

DESIGN

Cross-sectional study.

SETTING

Members of a traditional, communal, agrarian society living in South Dakota.

PARTICIPANTS

Ninety-five participants (mean age 39.8 years, 55% female) who were ≥ 19 years of age at the study's inception.

INTERVENTIONS

Not applicable.

MEASUREMENTS AND RESULTS

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.

CONCLUSIONS

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.

Sex-specific genetic architecture of asthma-associated quantitative trait loci in a founder population

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).

Schizophrenia and cancer: an epidemiological study

BACKGROUND

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.

AIMS

To study cancer incidence in schizophrenia.

METHOD

Cohort analysis of linked hospital and death records was used to compare cancer rates in people with schizophrenia with a reference cohort.

RESULTS

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).

CONCLUSIONS

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.

Sex differences in the genetic basis of morning serum cortisol levels: genome-wide screen identifies two novel loci specific to women

CONTEXT

Relatively little is known about the influence of specific genes on cortisol levels, particularly morning cortisol levels.

OBJECTIVE

The objective of this study was to identify quantitative trait loci associated with morning serum cortisol levels.

DESIGN

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.

SETTING

This study was conducted on nine communal Hutterite farms in South Dakota.

PARTICIPANTS

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.

MAIN OUTCOME MEASURES

The main outcome measures were markers significantly linked or associated with variation in morning serum cortisol levels.

RESULTS

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).

CONCLUSIONS

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.

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

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.

Appendicectomy, tonsillectomy, and inflammatory bowel disease: a case-control record linkage study

STUDY OBJECTIVE

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.

DESIGN

Nested case-control studies using a longitudinal database of linked hospital and death record abstracts.

SETTING

Southern England.

PATIENTS

Statistical records of people diagnosed with UC, CD, or a control condition admitted to hospitals in a defined area.

MAIN RESULTS

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.

CONCLUSIONS

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.

Depression and anxiety in people with inflammatory bowel disease

STUDY OBJECTIVE

To determine whether depression or anxiety co-occurs with ulcerative colitis (UC) or Crohn's disease (CD) more often than expected by chance, and, if so, whether the mental disorders generally precede or follow the inflammatory bowel diseases (IBD).

DESIGN

Nested case-control studies using a database of linked hospital record abstracts.

SETTING

Southern England.

MAIN RESULTS

Both depression and anxiety preceded UC significantly more often than would be predicted from the control population's experience. The associations were strongest when the mental conditions were diagnosed shortly before UC, although the association between depression and UC was also significant when depression preceded UC by five or more years. Neither depression nor anxiety occurred before CD more often than expected by chance. However, depression and anxiety were significantly more common after CD; the associations were strongest in the year after the initial record of CD. UC was followed by anxiety, but not by depression, more often than expected by chance and, again, the association was strongest within one year of diagnosis with UC.

CONCLUSIONS

The concentration of risk of depression or anxiety one year or less before diagnosis with UC suggests that the two psychiatric disorders might be a consequence of early symptoms of the as yet undiagnosed gastrointestinal condition. The data are also, however, compatible with the hypothesis that the psychiatric disorders could be aetiological factors in some patients with UC. Most of the excess anxiety or depression diagnosed subsequent to diagnosis of IBD occurs during the year after IBD is diagnosed and the probable explanation is that the mental disorders are sequelae of IBD.