Longitudinal changes in adverse effects reporting in multiple dietary supplement classifications: The US military dietary supplement use study

Over 70% of United States military service members (SMs) regularly use dietary supplements (DSs) and about 18% have reported adverse effects (AEs) associated with use. This investigation examined longitudinal changes in AEs reporting among DS users. On two separate occasions 1.3 ± 0.2 years apart (mean ± standard deviation), 5778 SMs completed identical questionnaires on DS use and associated AEs. Among SMs reporting DS use ≥1 time/week, ≥1 AE was reported by 19% and 15% in the baseline and follow-up phases, respectively. The risk of reporting DS use at follow-up was similar among those reporting and not reporting AEs at baseline for most DS categories including prohormones, proteins/amino acids, individual vitamins and minerals, multivitamin/multiminerals, herbals, fish oils, joint health products, and other DSs. An exception was combination products where those reporting AEs at baseline had an increased risk of use at follow-up (risk ratio = 1.13, 95% confidence interval = 1.06-1.09). Those reporting AEs at baseline and continuing DS use in the follow-up were more likely to report AEs at follow-up compared to those not reporting baseline AEs. In conclusion, AEs reported at baseline did not deter many participants from using DSs in the follow-up period, and many SMs reporting AEs at baseline continued reporting them at follow-up.

Lifetime Traumatic Brain Injury and Risk of Post-Concussive Symptoms in the Millennium Cohort Study

Traumatic brain injury (TBI) is prevalent among active duty military service members, with studies reporting up to 23% experiencing at least one TBI, with 10-60% of service members reporting at least one subsequent repeat TBI. A TBI has been associated with an increased risk of cumulative effects and long-term neurobehavioral symptoms, impacting operational readiness in the short-term and overall health in the long term. The association between multiple TBI and post-concussive symptoms (PCS), however, defined as symptoms that follow a concussion or TBI, in the military has not been adequately examined. Previous studies in military populations are limited by methodological issues including small sample sizes, the use of non-probability sampling, or failure to include the total number of TBI. To overcome these limitations, we examined the association between the total lifetime number of TBI and total number of PCS among U.S. active duty military service members who participated in the Millennium Cohort Study. A secondary data analysis was conducted using the Millennium Cohort Study's 2014 survey (n = 28,263) responses on self-reported TBI and PCS (e.g., fatigue, restlessness, sleep disturbances, poor concentration, or memory loss). Zero-inflated negative binomial models calculated prevalence ratios (PRs) and 95% confidence intervals (CIs) for the unadjusted and adjusted associations between lifetime TBIs and PCS. A third of military participants reported experiencing one or more TBIs during their lifetime with 72% reporting at least one PCS. As the mean number of PCS increased, mean lifetime TBIs increased. The mean number of PCS by those with four or more TBI (4.63) was more than twice that of those with no lifetime TBI (2.28). One, two, three, and four or more TBI had 1.10 (95% CI: 1.06-1.15), 1.19 (95% CI: 1.14-1.25), 1.23 (95% CI: 1.17-1.30), and 1.30 times (95% CI: 1.24-1.37) higher prevalence of PCS, respectively. The prevalence of PCS was 2.4 (95% CI: 2.32-2.48) times higher in those with post-traumatic stress disorder than their counterparts. Active duty military service members with a history of TBI are more likely to have PCS than those with no history of TBI. These results suggest an elevated prevalence of PCS as the number of TBI increased. This highlights the need for robust, longitudinal studies that can establish a temporal relationship between repetitive TBI and incidence of PCS. These findings have practical relevance for designing both workplace safety prevention measures and treatment options regarding the effect on and from TBI among military personnel.

Prevalence and adverse effects of sport-related nutritional supplements (sport drinks, bars, and gels) in the military before and during the COVID-19 pandemic: the US Military Dietary Supplement Use Study

BACKGROUND

Sport-related nutritional supplements (SRNS) include sport drinks, sport bars, and sport gels. This investigation examined temporal patterns in SRNS use and adverse effects (AEs) reported by a single cohort of United States active-duty service members (SMs) surveyed before and during the coronavirus disease 2019 (COVID-19) pandemic.

METHODS

A stratified random sample (n = 22,858) of SMs (Air Force, Army, Navy, and Marine Corps) who completed a questionnaire on their SRNS use and AE experiences and were still on active duty were asked to complete the identical questionnaire on a second occasion. Twenty-five percent of successfully contacted SMs completed both questionnaires (n = 5,778) and were included in this investigation. The average ± standard deviation time between questionnaires was 1.3 ± 0.2 years.

RESULTS

Prevalence of reported SRNS use ≥1 time/week in the baseline (BL) and follow-up (FU) phases were as follows: any SRNS: BL = 46%, FU = 41%; sport drinks: BL = 31%, FU = 28%; sport bars: BL = 30%, FU = 24%; sport gels: BL = 4%, FU = 4%. Reported weekly aerobic and resistance training durations were reduced in the FU period (8% and 26%, respectively). The proportion of SMs reporting SRNS use in both study phases was as follows: any SRNS = 62%, sport drinks = 54%, sport bars = 50%, sport gels = 35%. Prevalence of reported AEs in the BL and FU phases were as follows: any SRNS: BL = 1.9%, FU = 1.9%; sport drinks: BL = 1.0%, FU = 1.3%; sport bars: BL = 1.7%, FU = 1.4%; sport gels: BL = 3.3%, FU = 2.5%. The proportion of SMs reporting AEs in both phases was as follows: any SRNS = 14%, sport drinks = 11%, sport bars = 17%, sport gels = 0%.

CONCLUSIONS

Overall SRNS use prevalence decreased slightly in the FU period, possibly because of reduced physical training related to military restrictions imposed during the emergence of COVID-19 between surveys. A large proportion of SMs reported changing their use patterns in the FU with some discontinuing use and others initiating use. The AE incidence was similarly low in the BL and FU phases, and few SMs reported AEs in both phases suggesting AEs were transitory. AE reporting for SRNSs was much lower than previously found for dietary supplements, possibly because of greater government regulatory control over SRNSs.

The Medical Burden of Obesity and Overweight in the US Military: Association of BMI with Clinically Diagnosed Medical Conditions in United States Military Service Members

BACKGROUND

A high BMI is associated with various medical conditions, notably type 2 diabetes, cardiovascular disease, and mental health disorders. In the US military, BMI increased linearly between 1975 and 2015.

OBJECTIVE

This cross-sectional study investigated the associations between BMI and a comprehensive range of clinically diagnosed medical conditions (CDMCs) in US military service members (SMs).

METHODS

A stratified random sample of SMs (n=26,177) completed an online questionnaire reporting their height, weight, and demographic/lifestyle characteristics. Medical conditions for 6 mo before questionnaire completion were obtained from a comprehensive military electronic medical surveillance system and grouped into 39 CDMCs covering both broad (largely systemic) and specific medical conditions. BMI was calculated as weight/height2 (kg/m2). The prevalence of CDMCs was compared among normal weight (<25.0 kg/m2), overweight (25.0-29.9 kg/m2), and obese (≥30 kg/m2) SMs.

RESULTS

After multivariable adjustment for demographic/lifestyle characteristics, higher BMI was associated with higher odds of a diagnosed medical condition in 30 of 39 CDMCs, with all 30 displaying dose-response relationships. The 5 major CDMCs with the largest odds ratios comparing obese to normal weight were endocrine/nutritional/metabolic diseases (OR=2.67, 95%CI=2.24-3.15), nervous system diseases (odds ratio [OR]=2.59, 95%CI=2.32-2.90), circulatory system diseases (OR=2.56, 95%CI=2.15-3.06), musculoskeletal system diseases (OR=1.92, 95%CI=1.76-2.09), and mental/behavioral disorders (OR=1.69, 95%CI=1.51-1.90). Compared with normal weight SMs, overweight or obese SMs had a higher number of CDMCs (1.8±1.9 vs. 2.0±2.0 and 2.5±2.3, mean ± standard deviation, respectively, P<0.01).

CONCLUSIONS

In a young, physically active population, higher BMI was associated with a host of medical conditions, even after adjustment for demographic/lifestyle characteristics. The US Department of Defense should improve nutrition education and modify other factors that contribute to overweight and obesity. This study demonstrates that the medical burden of obesity is substantial in overweight and obese SMs.

Occupation and Risk of Traumatic Brain Injury in the Millennium Cohort Study

INTRODUCTION

Traumatic brain injury (TBI) is an occupational health hazard of military service. Few studies have examined differences in military occupational categories (MOC) which take into consideration the physical demands and job requirements across occupational groups.

METHODS

This study was approved by the University of Texas Health Science Center at Houston Institutional Review Board. Data for this cross-sectional study were obtained from the Naval Health Research Center's Millennium Cohort Study, an ongoing DoD study. Univariate analyses were employed to calculate frequencies and proportions for all variables. Bivariate analyses included unadjusted odds ratios (OR) and 95% CI for the association between all variables and TBI. Multivariable logistic regression was used to calculate adjusted ORs and 95% CIs to assess the association between MOC and TBI, adjusted for potential confounders: sex, race/ethnicity, rank, military status, branch of service, before-service TBI, and panel. Logistic regression models estimated odds of TBI for each MOC, and stratified models estimated odds separately for enlisted and officer MOCs.

RESULTS

Approximately 27% of all participants reported experiencing a service-related TBI. All MOCs were statistically significantly associated with increased odds of service-related TBI, with a range of 16 to 45%, except for "Health Care" MOCs (OR: 1.01, 95% CI 0.91-1.13). Service members in "Infantry/Tactical Operations" had the highest odds (OR: 1.45, 95% CI 1.31-1.61) of service-related TBI as compared to "Administration & Executives." Among enlisted service members, approximately 28% reported experiencing a service-related TBI. Among enlisted-specific MOCs, the odds of TBI were elevated for those serving in "Infantry, Gun Crews, Seamanship (OR: 1.79, 95% CI 1.58-2.02)," followed by "Electrical/Mechanical Equipment Repairers (OR: 1.23, 95% CI 1.09-1.38)," "Service & Supply Handlers (OR 1.21, 95% CI 1.08-1.37)," "Other Technical & Allied Specialists (OR 1.21, 95% CI 1.02-1.43)," "Health Care Specialists (OR 1.19, 95% CI 1.04-1.36)," and "Communications & Intelligence (OR: 1.16, 95% CI 1.02-1.31)," compared to "Functional Support & Administration." Among officer service members, approximately 24% reported experiencing a service-related TBI. After adjustment the odds of TBI were found to be significant for those serving as "Health Care Officers" (OR: 0.65, 95% CI: 0.52-0.80) and "Intelligence Officers" (OR: 1.27, 95% CI: 1.01-1.61).

CONCLUSIONS

A strength of this analysis is the breakdown of MOC associations with TBI stratified by enlisted and officer ranks, which has been previously unreported. Given the significantly increased odds of service-related TBI reporting within enlisted ranks, further exploration into the location (deployed versus non-deployed) and mechanism (e.g., blast, training, sports, etc.) for these injuries is needed. Understanding injury patterns within these military occupations is necessary to increase TBI identification, treatment, and foremost, prevention.Results highlight the importance of examining specific occupational categories rather than relying on gross categorizations, which do not account for shared knowledge, skills, and abilities within occupations. The quantification of risk among enlisted MOCs suggests a need for further research into the causes of TBI.

Assessing Injury Susceptibility at Marine Corps Recruit Depot, San Diego, California

ABSTRACT

Poh, PYS, Sessoms, PH, Haluch, KS, and Trone, DW. Assessing injury susceptibility at Marine Corps Recruit Depot, San Diego, California. J Strength Cond Res 37(7): 1530-1536, 2023-Marine Corps Recruit Depot (MCRD) recruits undergo demanding training. Musculoskeletal injury (MSKI) accounts for attrition and graduation delays. Functional tests, such as Functional Movement Screen (FMS), Y-Balance Test-Lower Quarter (YBT-LQ), and ankle dorsiflexion range of motion (AD-ROM), may identify individuals at greater MSKI risk. This study tested the hypothesis that functional assessments may inform injury prediction. Male recruits ( N = 407; mean ± SD : age, 20 ± 2 years) performed baseline functional tests. Marine Corps Recruit Depot staff tracked MSKI and graduation outcomes. The chi-square test of independence (individual FMS exercises) and Mann-Whitney U (FMS composite score) test examined the relationship between FMS and MSKI incidence. One-way analysis of variance compared YBT-LQ and AD-ROM with MSKI incidence. Twelve recruits (3%) incurred a lower extremity MSKI and were dropped. Of those 12, 9 had a delayed graduation, and 3 separated from enlistment. The level of significance was set at p < 0.10 to identify between-group differences (yes-MSKI vs. no-MSKI). Functional movement screen composite score ( p = 0.064), hurdle step ( p = 0.059), and trunk stability ( p = 0.001) were lower in yes-MSKI. Y-Balance Test-Lower Quarter anterior direction difference between legs ( p = 0.011) and AD-ROM right side ( p = 0.055) was greater in yes-MSKI. Odds ratios (OR) were calculated using cut-off scores, with strong odds of sustaining MSKI with FMS trunk stability score <2 (OR: 7.56, 95% confidence interval [CI]: [2.32, 24.61]) and YBT-LQ anterior difference >6.25 cm (OR: 6.38, 95% CI: [1.98, 20.55]). Recruits who incurred MSKI had scores that indicated lesser mobility and stability of the lower extremity, providing preliminary evidence that when assessed together, FMS, YBT-LQ, and AD-ROM, may have predictive value for identifying those at MSKI risk.

Associations between clinically diagnosed medical conditions and dietary supplement use: the US military dietary supplement use study

OBJECTIVE

This study examined associations between multiple dietary supplement (DS) categories and medical conditions diagnosed by health professionals.

DESIGN

Cross-sectional.

SETTING

Volunteers completed an online questionnaire on DS use and demographic/lifestyle factors. Medical diagnoses were obtained from a comprehensive military electronic medical surveillance system and grouped into twenty-four clinically diagnosed medical conditions (CDMC).

PARTICIPANTS

A stratified random sample of US service members (SM) from all military services (n 26 680).

RESULTS

After adjustment for demographic/lifestyle factors (logistic regression), higher risk was found for 92 % (22/24) of CDMC among individual vitamins/minerals users, 58 % (14/24) of CDMC among herbal users, 50 % (12/24) of CDMC among any DS users and 46 % (11/24) of CDMC among multivitamins/multiminerals (MVM) users. Among protein/amino acid (AA) users, risk was lower in 25 % (6/24) of CDMC. For combination products, risk was higher in 13 % (3/24) of CDMC and lower in 8 % (2/24). The greater the number of CDMC, the higher the prevalence of DS use in most DS categories except proteins/AA where prevalence decreased.

CONCLUSIONS

Users in many DS categories had a greater number of CDMC, but protein/AA users had fewer CDMC; results for combination products were mixed. These data indicate those with certain CDMC were also users in some DS categories, especially individual vitamins/minerals, herbals and MVM. Data are consistent with the perception that use of DS enhances health, especially in those with CDMC. Protein/AA and combination product users were more likely to be younger, more physically active men, factors that likely reduced CDMC.

Single and repeated high-level blast, low-level blast, and new-onset self-reported health conditions in the U.S. Millennium Cohort Study: An exploratory investigation

Introduction

Although previous research suggests that overpressure exposure from either high-level blast (HLB) or low-level blast (LLB) are harmful to health, to date no large-scale studies with representative samples of military personnel have utilized prospective designs and self-reported measures to examine the relationships between blast exposure and health conditions. To address these limitations, this analysis of data from the Millennium Cohort Study (MCS), the largest and longest running study of U.S. service members and veterans, examined (1) whether single or repeated HLB exposure is associated with self-reported diagnoses of illness and injury, (2) whether repeated HLB is associated with greater risk than single HLB, (3) potential adverse consequences of LLB exposure using military occupation as a proxy, and (4) the combined effects of single or repeated HLB and LLB exposure.

Method

MCS participants who completed the 2011-2013 survey (N = 138,949) were classified as having been exposed to "no," "single," or "repeated" HLB exposure, and into low or high risk of exposure to LLB based on occupation. Participants self-reported diagnosis of 45 medical conditions; newly reported diagnoses were regressed on single and repeated (vs. no) HLB, occupational risk of LLB, and relevant interactions using logistic regression.

Results

Single and repeated HLB were associated with new onset of 25 and 29 diagnoses, respectively; repeated HLB exposure was associated with greater risk than single HLB exposure for five diagnoses (e.g., PTSD, depression). Occupational risk of LLB was associated with 11 diagnoses (e.g., PTSD, significant hearing loss). Additionally, 14 significant interactions were detected across 11 diagnoses.

Discussion

Findings suggest that overpressure exposure (including single HLB, repeated HLB, and occupational risk of LLB) may increase the risks of self-reporting clinical diagnoses of PTSD, hearing loss, chronic fatigue syndrome, neuropathy-caused reduced sensation in the hands and feet, depression, vision loss, sinusitis, reflux, and anemia. Furthermore, the combination of HLB and LLB exposure may be associated with greater risk of migraines, PTSD, and impaired fecundity. These findings provide further evidence of the potential adverse consequences associated with overpressure exposure and underscore the necessity of public health surveillance initiatives for blast exposure and/or safety recommendations for training and operational environments.

Short sleep duration is associated with a wide variety of medical conditions among United States military service members

OBJECTIVES

This cross-sectional study investigated self-reported sleep duration and its association with a comprehensive range of clinically-diagnosed medical condition categories (CDMCs), as well as the relationship between short sleep duration (≤6 h) and demographic/lifestyle factors, among United States military service members (SMs).

METHODS

A stratified random sample of SMs (n = 20,819) completed an online questionnaire on usual daily hours of sleep and demographic/lifestyle characteristics. CDMCs for a six-month period prior to questionnaire completion were obtained from a comprehensive military electronic medical surveillance system and grouped into 33 CDMCs covering both broad and specific medical conditions. Prevalence of CDMCs was compared among three sleep duration categories (≤4, 5-6 and ≥7 h).

RESULTS

SMs reported a mean ± standard deviation of 6.3 ± 1.4 h of sleep per day. After adjustment for demographic/lifestyle characteristics, shorter sleep duration was associated with higher odds of a medical condition in 25 of 33 CDMCs, with most (n = 20) demonstrating a dose-response relationship. The five CDMCs with the largest differences between ≤4 vs ≥ 7 h sleep were: diseases of the nervous system (odds ratio [OR] = 2.9, 95% confidence interval [95%CI] = 2.4-3.4), mental/behavioral diseases (OR = 2.7, 95%CI = 2.3-3.2), diseases of the musculoskeletal system (OR = 1.9, 95%CI = 1.6-2.1), diseases of the circulatory system (OR = 1.7, 95%CI = 1.3-2.2), and diseases of the digestive system (OR = 1.6, 95%CI = 1.2-2.0). Six hours of sleep or less was independently associated with older age, less formal education, race, Hispanic ethnicity, higher body mass index, smoking, and military service branch.

CONCLUSIONS

In this young, physically active population, reporting shorter sleep duration was associated with a higher risk of multiple CDMCs.

Prescription medication use of United States military service members by therapeutic classification

Background: This cross-sectional study investigated the prevalence of, and factors associated with, filled prescription medications (FPMs) among United States (US) service members (SMs).

Methods: A stratified random sample of active duty SMs from the Air Force, Army, Marine Corps, and Navy was obtained from military workforce records. Participants (n = 26,680) completed a questionnaire on demographics, physical characteristics, and lifestyle factors and approved access to their FPM for the previous 6 months. FPMs were obtained from the military Pharmacy Data Transaction Service that included all prescription medications dispensed at military medical treatment facilities, abroad, at retail pharmacies in the US, and/or through mail-order programs.

Results: About two-thirds (65%) of SMs had ≥1 FPM in the 6 months surveillance period. Central nervous system (CNS) agents had the highest prevalence (41%), followed by anti-infective agents (20%), eye/ear/nose/throat preparations (20%), gastrointestinal drugs (18%), autonomic drugs (17%), skin and mucous membrane agents (13%), antihistamine drugs (12%), respiratory tract agents (12%) and cardiovascular drugs (9%). Among CNS agents, overall prevalence of dispensed non-steroidal anti-inflammatory drug (NSAIDs) was 30%. The odds of any FPM was independently associated with female gender, older age, higher body mass index, former tobacco use (smoking and smokeless tobacco), lower alcohol consumption, and was highest among Army, lowest among Marine Corps personnel.

Conclusion: In this sample of SMs, dispensing of prescription medication was high, especially NSAIDs, but dispensing of cardiovascular drugs was much lower compared to the general US population, likely because of the younger age and higher level of physical activity of SMs.

Prevalence of caffeine consumers, daily caffeine consumption, and factors associated with caffeine use among active duty United States military personnel

Background

Although representative data on caffeine intake in Americans are available, these data do not include US service members (SMs). The few previous investigations in military personnel largely involve convenience samples. This cross-sectional study examined prevalence of caffeine consumers, daily caffeine consumption, and factors associated with caffeine use among United States active duty military service members (SMs).

Methods

A stratified random sample of SMs were asked to complete an on-line questionnaire on their personal characteristics and consumption of caffeinated products (exclusive of dietary supplements). Eighteen percent (n = 26,680) of successfully contacted SMs (n = 146,365) completed the questionnaire.

Results

Overall, 87% reported consuming caffeinated products ≥1 time/week. Mean ± standard error per-capita consumption (all participants) was 218 ± 2 and 167 ± 3 mg/day for men and women, respectively. Caffeine consumers ingested 243 ± 2 mg/day (251 ± 2 mg/day men, 195 ± 3 mg/day women). On a body-weight basis, men and women consumed respectively similar caffeine amounts (2.93 vs 2.85 mg/day/kg; p = 0.12). Among individual caffeinated products, coffee had the highest use (68%), followed by sodas (42%), teas (29%), energy drinks (29%) and gums/candy/medications (4%). In multivariable logistic regression, characteristics independently associated with caffeine use (≥1 time/week) included female gender, older age, white race/ethnicity, higher body mass index, tobacco use or former use, greater alcohol intake, and higher enlisted or officer rank.

Conclusion

Compared to National Health and Nutrition Examination Survey data, daily caffeine consumption (mg/day) by SMs was higher, perhaps reflecting higher mental and physical occupational demands on SMs.

Adverse effects associated with use of specific dietary supplements: The US Military Dietary Supplement Use Study

Dietary supplements (DSs) are used by 50% of Americans and 70% of United States military service members (SMs); some have adverse effects (AEs). This cross-sectional investigation examined AEs associated with specific DSs. A stratified random sample of SMs from the Air Force, Army, Marine Corps, and Navy was obtained. Volunteers completed a questionnaire reporting AEs for 96 generic and 62 specific DSs. The highest prevalence (≥1 AE) in specific DS categories was 35% prohormones, 33% weight loss supplements, 26% pre/post workout supplements, 14% herbal products, 12% multivitamin/multiminerals, 11% protein/amino acids, 9% muscle building supplements, 7% other DSs, 6% joint health products, and 5% individual vitamins/minerals. Specific DSs of concern (with proportion reporting AEs) included: Libido Max® (35%), Hydroxycut Hardcore® (33%), OxyElite® (33%), Roxylean® (31%), Growth Factor 9® (30%), Super HD® (29%), Hydroxycut Advanced® (29%), Lipo 6® (28%), The Ripper® (27%), Test Booster® (27%), Xenadrine Xtreme Thermogenic® (27%), C4 Extreme® (26%), and C4 Origional® (25%). Products marketed for weight loss, use before/after workout, and prohormones had the highest AE prevalence. DSs can contain substances with independent/additive AEs and/or interact with other ingredients or prescribed medications. Methods described here could provide a continuous surveillance system detecting dangerous DSs entering the market.

The Millennium Cohort Study: The First 20 Years of Research Dedicated to Understanding the Long-Term Health of US Service Members and Veterans

The Millennium Cohort Study, the US Department of Defense's largest and longest running study, was conceived in 1999 to investigate the effects of military service on service member health and well-being by prospectively following active duty, Reserve, and National Guard personnel from all branches during and following military service. In commemoration of the Study's 20th anniversary, this paper provides a summary of its methods, key findings, and future directions. Recruitment and enrollment of the first 5 panels occurred between 2001 and 2021. After completing a baseline survey, participants are requested to complete follow-up surveys every 3 to 5 years. Study research projects are categorized into 3 core portfolio areas (psychological health, physical health, and health-related behaviors) and several cross-cutting areas and have culminated in more than 120 publications to date. For example, some key Study findings include that specific military service-related factors (e.g., experiencing combat, serving in certain occupational subgroups) were associated with adverse health-related outcomes and that unhealthy behaviors and mental health issues may increase following the transition from military service to veteran status. The Study will continue to foster stakeholder relationships such that research findings inform and guide policy initiatives and health promotion efforts.

Prevalence of and Factors Associated with Dietary Supplement Use in a Stratified, Random Sample of US Military Personnel: The US Military Dietary Supplement Use Study

BACKGROUND

About 50% of Americans and 70% of US military service members use dietary supplements (DSs).

OBJECTIVES

This cross-sectional survey examined current prevalence of and factors associated with DS use in service members.

METHODS

A stratified random sample of 200,000 service members from the Air Force, Army, Marine Corps, and Navy was obtained from military manpower records, and these service members were asked to complete a questionnaire on their DS use and personal characteristics. Chi-square statistics and multivariable logistic regression examined differences across various strata of demographic, lifestyle, and military characteristics.

RESULTS

About 18% of successfully contacted service members (n = 26,681) completed the questionnaire between December 2018 and August 2019 (mean ± SD age: 33 ± 8 y, 86% male). Overall, 74% reported using ≥1 DS/wk. Multivitamins/multiminerals were the most commonly used DSs (45%), followed by combination products (44%), proteins/amino acids (42%), individual vitamins/minerals (31%), herbals (20%), joint health products (9%), and purported prohormones (5%). In multivariable analysis, factors independently associated with DS use included female gender [OR (female/male): 1.91; 95% CI: 1.73, 2.11], older age [OR (≥40/18-24 y): 1.25; 95% CI: 1.08, 1.44], higher education level [OR (college degree/high school or less): 1.35; 95% CI: 1.19, 1.53], higher BMI [OR (≥30/<25 kg/m2): 1.37; 95% CI: 1.25, 1.52], more weekly resistance training [OR (>300/≤45 min/wk): 5.05; 95% CI: 4.55, 5.61], smokeless tobacco use [OR (user/nonuser): 1.30; 95% CI: 1.17, 1.44], higher alcohol intake [OR (≥72/0 mL/wk): 1.41; 95% CI: 1.29, 1.54], and higher military rank [OR (senior officer/junior enlisted): 1.26; 95% CI: 1.06, 1.51].

CONCLUSIONS

Compared with civilian data from the NHANES, service members were much more likely to use DSs and used different types of DSs, especially combination products and proteins/amino acids often used to purportedly enhance physical performance. Comparisons with previous military data suggest DS use has increased over time.

Prevalence, factors associated with use, and adverse effects of sport-related nutritional supplements (sport drinks, sport bars, sport gels): the US military dietary supplement use study

Background

Sport-related nutritional supplements (SRNSs) include sport drinks, sport bars, and sport gels. Previous studies indicate that 25–35 % of athletes and 25–50 % of military personnel report using these supplements. This study examined prevalence, factors associated with use, and adverse effects (AEs) of SRNSs among United States military service members (SMs).

Methods

A stratified random sample of 200,000 SMs was obtained from military workforce records, and asked to complete a survey on demographics, SRNS use, and AEs experienced. About 18 % (n = 26,681) of contacted SMs (n = 146,365) completed the survey between December 2018 and August 2019.

Results

Overall, 45 % of SMs used ≥ 1 SRNS at least once per week in the past 6 months. Prevalence of use (± standard error) for sport drinks, bars, and gels were 32 ± 0.3, 27 ± 0.3, and 3 ± 0.1 %, respectively. Use of 1, 2, or 3 SRNSs was 28.9 ± 0.5, 13.6 ± 0.6, and 2.2 ± 0.6 %, respectively. Multivariable logistic regression indicated greater use of any SRNS was independently associated with male gender, younger age, single marital status, more weekly aerobic or resistance training, tobacco use, higher alcohol intake, officer status, combat arms occupations, and service in the Marine Corps or Navy (compared to the Air Force). Overall, the proportion of users reporting ≥ 1 AE was 2.0 ± 0.1 %, with 1.3 ± 0.1 % for sport drinks, 1.6 ± 0.2 % for sport bars, and 2.8 ± 0.6 % for sport gels.

Conclusions

This large study of a stratified random sample of SMs found that nearly half of SMs consumed SRNSs weekly, and self-reported AEs were comparatively low. The AE incidence for SRNSs was much lower than typically found for dietary supplements, possibly because of more rigorous regulatory oversight for SRNSs.

Prevalence of and Factors Associated with Dietary Supplement Use in a Stratified, Random Sample of US Military Personnel: The US Military Dietary Supplement Use Study

BACKGROUND

About 50% of Americans and 70% of US military service members use dietary supplements (DSs).

OBJECTIVES

This cross-sectional survey examined current prevalence of and factors associated with DS use in service members.

METHODS

A stratified random sample of 200,000 service members from the Air Force, Army, Marine Corps, and Navy was obtained from military manpower records, and these service members were asked to complete a questionnaire on their DS use and personal characteristics. Chi-square statistics and multivariable logistic regression examined differences across various strata of demographic, lifestyle, and military characteristics.

RESULTS

About 18% of successfully contacted service members (n = 26,681) completed the questionnaire between December 2018 and August 2019 (mean ± SD age: 33 ± 8 y, 86% male). Overall, 74% reported using ≥1 DS/wk. Multivitamins/multiminerals were the most commonly used DSs (45%), followed by combination products (44%), proteins/amino acids (42%), individual vitamins/minerals (31%), herbals (20%), joint health products (9%), and purported prohormones (5%). In multivariable analysis, factors independently associated with DS use included female gender [OR (female/male): 1.91; 95% CI: 1.73, 2.11], older age [OR (≥40/18-24 y): 1.25; 95% CI: 1.08, 1.44], higher education level [OR (college degree/high school or less): 1.35; 95% CI: 1.19, 1.53], higher BMI [OR (≥30/<25 kg/m2): 1.37; 95% CI: 1.25, 1.52], more weekly resistance training [OR (>300/≤45 min/wk): 5.05; 95% CI: 4.55, 5.61], smokeless tobacco use [OR (user/nonuser): 1.30; 95% CI: 1.17, 1.44], higher alcohol intake [OR (≥72/0 mL/wk): 1.41; 95% CI: 1.29, 1.54], and higher military rank [OR (senior officer/junior enlisted): 1.26; 95% CI: 1.06, 1.51].

CONCLUSIONS

Compared with civilian data from the NHANES, service members were much more likely to use DSs and used different types of DSs, especially combination products and proteins/amino acids often used to purportedly enhance physical performance. Comparisons with previous military data suggest DS use has increased over time.

Association Between Dietary Supplement Use and ICD-9-CM Code Classification in Active Duty US Navy and Marine Corps Service Members

INTRODUCTION

This study is the first to our knowledge to examine associations of survey-reported dietary supplement use with medical record diagnoses, rather than retrospective self-reported supplement use at the time of the medical encounter or case reports of adverse events. Dietary supplement (DS) use and adverse events associations in US Navy and Marine Corps personnel remains unknown. This study assessed associations of DS use in active duty (AD) personnel with ICD-9-CM diagnostic codes from outpatient medical encounters from the Military Health System Data Repository (MDR).

MATERIALS AND METHODS

This cross-sectional investigation used a one-time survey of DS use among AD conducted August through December 2014. Survey data were matched to MDR data accessed in September 2016, and associations between the survey responses and diagnoses were analyzed. Statistical significance was set at alpha level 0.005, and 99.5% confidence intervals (CIs) were calculated. MDR data were matched with survey results for 1,708 personnel. Multivariable logistic regression analyses examined whether use of specific classes of supplements was associated with disease.

RESULTS

Results revealed significant associations between vitamin supplement use and ICD-9-CM-diagnosed diseases of the nervous system (odds ratio [OR]: 1.72, 99.5% CI: 1.11-2.68) and diseases of the musculoskeletal system and connective tissue (OR: 1.59, 99.5% CI: 1.17-2.17). Joint health supplement category use was associated with diseases of the musculoskeletal system and connective tissue (OR: 1.81, 99.5% CI: 1.12-2.94) and injury and poisoning (OR: 1.82, 99.5% CI: 1.10-3.04).

CONCLUSIONS

The percentages of service members with diseases in specific ICD-9-CM diagnostic categories were similar to those reported in other studies using military medical data. There is a greater prevalence of dietary supplement use by the service members who participated in this survey compared with the general population, with 73% of US Navy and Marine Corps personnel reporting use of dietary supplements one or more times per week compared to the estimated 50% of all Americans currently using some form of dietary supplement. The DoD ensures the optimal readiness, performance, and health of its military service members, thus future longitudinal evaluation of dietary supplement use by this population will test the preliminary findings of this study.

Smoking and drinking behaviors of military spouses: Findings from the Millennium Cohort Family Study

INTRODUCTION

The associations between stressful military experiences and tobacco use and alcohol misuse among Service members are well documented. However, little is known about whether stressful military experiences are associated with tobacco use and alcohol misuse among military spouses.

METHODS

Using 9872 Service member-spouse dyads enrolled in the Millennium Cohort Family Study, we employed logistic regression to estimate the odds of self-reported cigarette smoking, risky drinking, and problem drinking among spouses by Service member deployment status, communication regarding deployment, and stress associated with military-related experiences, while adjusting for demographic, mental health, military experiences, and Service member military characteristics.

RESULTS

Current cigarette smoking, risky drinking, and problem drinking were reported by 17.2%, 36.3%, and 7.3% of military spouses, respectively. Current deployment was not found to be associated with spousal smoking or drinking behaviors. Communication about deployment experiences with spouses was associated with lower odds of smoking, but not with risky or problem drinking. Spouses bothered by communicated deployment experiences and those who reported feeling very stressed by a combat-related deployment or duty assignment had consistently higher odds of both risky and problem drinking.

CONCLUSIONS

Our findings suggest that contextual characteristics about the deployment experience, as well as the perceived stress of those experiences, may be more impactful than the simple fact of Service member deployment itself. These results suggest that considering the impact of deployment experiences on military spouses reveals important dimensions of military community adaptation and risk.

Caffeine Use among Active Duty Navy and Marine Corps Personnel

Data from the National Health and Nutrition Examination Survey (NHANES) indicate 89% of Americans regularly consume caffeine, but these data do not include military personnel. This cross-sectional study examined caffeine use in Navy and Marine Corps personnel, including prevalence, amount of daily consumption, and factors associated with use. A random sample of Navy and Marine Corps personnel was contacted and asked to complete a detailed questionnaire describing their use of caffeine-containing substances, in addition to their demographic, military, and lifestyle characteristics. A total of 1708 service members (SMs) completed the questionnaire. Overall, 87% reported using caffeinated beverages ≥1 time/week, with caffeine users consuming a mean ± standard error of 226 ± 5 mg/day (242 ± 7 mg/day for men, 183 ± 8 mg/day for women). The most commonly consumed caffeinated beverages (% users) were coffee (65%), colas (54%), teas (40%), and energy drinks (28%). Multivariable logistic regression modeling indicated that characteristics independently associated with caffeine use (≥1 time/week) included older age, white race/ethnicity, higher alcohol consumption, and participating in less resistance training. Prevalence of caffeine use in these SMs was similar to that reported in civilian investigations, but daily consumption (mg/day) was higher.

Sleep and Health Resilience Metrics in a Large Military Cohort

STUDY OBJECTIVES

Examine the relationship between self-reported sleep parameters and indicators of resilience in a US military population (n = 55,021).

METHODS

Longitudinal analyses (2001-2008) were conducted using subjective data collected from Millennium Cohort Study questionnaires and objective data from military records that included demographics, military health, and deployment information. Subjective sleep duration and insomnia symptoms were collected on the study questionnaire. Resilience metrics included lost work days, self-rated health, deployment, frequency and duration of health care utilization, and early discharge from the military. Generalized estimating equations and survival analyses were adjusted for demographic, military, behavioral, and health covariates in all models.

RESULTS

The presence of insomnia symptoms was significantly associated with lower self-rated health, more lost work days, lower odds of deployment, higher odds of early discharge from military service early, and more health care utilization. Those self-reporting < 6 h (short sleepers) or > 8 h (long sleepers) of sleep per night had similar findings, except for the deployment outcome in which those with the shortest sleep were more likely to deploy.

CONCLUSIONS

Poor sleep is a detriment to service members' health and readiness. Leadership should redouble efforts to emphasize the importance of healthy sleep among military service members, and future research should focus on the efficacy of interventions to promote healthy sleep and resilience in this population.

COMMENTARY

A commentary on this article appears in this issue on page 963.

Recent Sexual Trauma and Adverse Health and Occupational Outcomes Among U.S. Service Women

Sexual trauma is prevalent among military women, but data on potential effects are needed. The association of sexual trauma with health and occupational outcomes was investigated using longitudinal data from the Millennium Cohort Study. Of 13,001 U.S. service women, 1,364 (10.5%) reported recent sexual harassment and 374 (2.9%) recent sexual assault. Women reporting recent sexual harassment or assault were more likely to report poorer mental health: OR = 1.96, 95% CI [1.71, 2.25], and OR = 3.45, 95% CI [2.67, 4.44], respectively. They reported poorer physical health: OR = 1.39, 95% CI [1.20, 1.62], and OR = 1.39, 95% CI [1.04, 1.85], respectively. They reported difficulties in work/activities due to emotional health: OR = 1.80, 95% CI [1.59, 2.04], and OR = 2.70, 95% CI [2.12, 3.44], respectively. They also reported difficulties with physical health: OR = 1.55, 95% CI [1.37, 1.75], and OR = 1.52 95% CI [1.20, 1.91], respectively, after adjustment for demographic, military, health, and prior sexual trauma characteristics. Recent sexual harassment was associated with demotion, OR = 1.47, 95% CI [1.12, 1.93]. Findings demonstrated that sexual trauma represents a potential threat to military operational readiness and draws attention to the importance of prevention strategies and services to reduce the burden of sexual trauma on military victims.

Longitudinal Investigation of Smoking Initiation and Relapse Among Younger and Older US Military Personnel

OBJECTIVES

We examined whether military service, including deployment and combat experience, were related to smoking initiation and relapse.

METHODS

We included older (panel 1) and younger (panel 2) participants in the Millennium Cohort Study. Never smokers were followed for 3 to 6 years for smoking initiation, and former smokers were followed for relapse. Complementary log-log regression models estimated the relative risk (RR) of initiation and relapse by military exposure while adjusting for demographic, health, and lifestyle factors.

RESULTS

Deployment with combat experience predicted higher initiation rate (panel 1: RR = 1.44; 95% confidence interval [CI] = 1.28, 1.62; panel 2: RR = 1.26; 95% CI = 1.04, 1.54) and relapse rate (panel 1 only: RR = 1.48; 95% CI = 1.36, 1.62). Depending on the panel, previous mental health disorders, life stressors, and other military and nonmilitary characteristics independently predicted initiation and relapse.

CONCLUSIONS

Deployment with combat experience and previous mental disorder may identify military service members in need of intervention to prevent smoking initiation and relapse.

The association of self-reported measures with poor training outcomes among male and female U.S. Navy recruits

This prospective study evaluated the association of self-reported health habits and behaviors in 2,930 Navy recruits with poor training outcomes, defined as graduating late or separating from training. Although 17% of the men and 21% of the women had a poor training outcome, results suggest that some self-reported measures were associated with poor training outcomes. Men who did not run or jog at least 1 month before basic training or had a previous lower limb injury without complete recovery and women reporting the same or less physical activity compared with their same-age counterparts were more likely to have a poor training outcome. An important first step in decreasing poor training outcomes is encouraging incoming recruits to participate in physical activity and taking steps to identify and rehabilitate recruits who are not completely healed from a lower limb musculoskeletal injury before reporting to basic training.

Injury reduction effectiveness of assigning running shoes based on plantar shape in Marine Corps basic training

BACKGROUND

Shoe manufacturers market motion control, stability, and cushioned shoes for plantar shapes defined as low, normal, and high, respectively. This assignment procedure is presumed to reduce injuries by compensating for differences in running mechanics.

HYPOTHESIS

Assigning running shoes based on plantar shape will not reduce injury risk in Marine Corps basic training.

STUDY DESIGN

Randomized controlled clinical trial; Level of evidence, 1.

METHODS

After foot examinations, Marine Corps recruits in an experimental group (E: 408 men, 314 women) were provided motion control, stability, or cushioned shoes for plantar shapes indicative of low, medium, or high arches, respectively. A control group (C: 432 men, 257 women) received a stability shoe regardless of plantar shape. Injuries during the 12 weeks of training were determined from outpatient visits obtained from the Defense Medical Surveillance System. Other known injury risk factors (eg, fitness, smoking, prior physical activity) were obtained from a questionnaire, existing databases, or the training units.

RESULTS

Cox regression indicated little difference in injury risk between the E and C groups among men (hazard ratio [E/C] = 1.01; 95% confidence interval, 0.82-1.24) or women (hazard ratio [E/C] = 0.88; 95% confidence interval, 0.70-1.10).

CONCLUSION

This prospective study demonstrated that assigning shoes based on the shape of the plantar foot surface had little influence on injuries even after considering other injury risk factors.

Is radiographic vertebral fracture a risk factor for mortality?

Clinical fractures predict increased mortality risk, but few studies report mortality based on prevalent radiographically defined vertebral fracture. This study examined whether radiographically defined vertebral fracture is a risk factor for mortality in older adults. The 1,580 participants in California (631 men, 949 women) were aged > or =50 years in 1992-1996. Lateral spine radiographs, and information about medical history and behaviors, were obtained. Overall, 55 (8.7%) men and 123 (13%) women had at least one prevalent fracture at baseline; of these, 48 women and 14 men had two or more. Over 7.6 years, 460 participants died, 27.6% without and 41.0% with prevalent fractures (p < 0.001). Prevalent vertebral fracture was not associated with all-cause mortality in both sexes combined (adjusted hazard ratio = 1.09, 95% confidence interval: 0.84, 1.42) or sex-specific analyses (women: adjusted hazard ratio = 1.15, 95% confidence interval: 0.83, 1.59; men: adjusted hazard ratio = 0.89, 95% confidence interval: 0.55, 1.46). However, women with two or more prevalent fractures had increased risk of all-cause mortality (adjusted hazard ratio = 1.56, 95% confidence interval: 1.01, 2.40; p = 0.04). Women with any prevalent vertebral fractures also had increased mortality risk from "other" causes (adjusted hazard ratio = 1.59, 95% confidence interval: 1.03, 2.45; p = 0.04) but not cardiovascular disease or cancer. A single radiographic vertebral fracture is not a risk for mortality in older women; larger, longer studies of men and those with two or more radiographic vertebral fractures are needed.

Factors associated with discharge during marine corps basic training

This prospective study assessed risk factors for discharge from basic training (BT) among 2,137 male Marine Corps recruits between February and April 2003. Physical and demographic characteristics, exercise, and previous lower extremity injuries before arrival at Marine Corps Recruit Depot were assessed by questionnaire during intake processing. Stress fractures were confirmed by x-ray, triple-phase bone scan, or magnetic resonance imaging. Overall, 223 (10.4%) participants were discharged from training. In addition to the occurrence of a stress fracture during BT, older age (>23 years), non-Hispanic race, poor incoming self-rated physical fitness, no history of competitive exercise, and an incoming lower extremity injury with incomplete recovery were independent risk factors for discharge. Strategies to identify and allow the proper healing time for pre-BT lower extremity injuries, including interventions to improve the physical fitness of recruits before BT and reduce stress fractures during BT, may be indicated to lower attrition.

Negative first-term outcomes associated with lower extremity injury during recruit training among female Marine Corps graduates

This study assessed the impact of lower extremity injuries and stress fractures during recruit training on first-term outcomes among female Marine Corps graduates. Injury data were collected from women recruits at Parris Island, South Carolina (1995-1999) and negative first-term outcomes were obtained from the Career History Archival Medical and Personnel System. The three negative outcomes included (1) failure to complete first-term of service, (2) failure to achieve rank of corporal, and (3) failure to reenlist. Overall, 22% did not complete their first-term enlistment and 12% of those who did were not promoted to corporal. After adjustment for demographic characteristics, not completing first term and not being promoted to corporal were both associated with injuries or stress fracture during training. Reenlistment was not associated with training injuries. Our findings indicate lower extremity injuries among women undergoing Marine Corps recruit training are associated with poor first-term outcomes even among those who graduate.

Epidemiology of Stress Fracture and Lower-Extremity Overuse Injury in Female Recruits

PURPOSE

The purpose of this prospective study was to examine rates and risk factors for overuse injuries among 824 women during Marine Corps Recruit Depot basic training at Parris Island, SC, in 1999.

METHODS

Data collected included training day exposures (TDE), baseline performance on a standardized 1.5-mile timed run, and a pretraining questionnaire highlighting exercise and health habits. The women were followed during training for occurrence of stress fracture and other lower-extremity overuse injury.

RESULTS

There were 868 lower-extremity overuse injuries for an overall injury rate of 12.6/1000 TDE. Rates for initial and subsequent injury were 8.7/1000 and 20.7/1000 TDE, respectively. There were 66 confirmed lower-extremity stress fractures among 56 (6.8%) women (1.0/1000 TDE). Logistic regression modeling indicated that low aerobic fitness (a slower time on the timed run (> 14.4 min)), no menses in six or more consecutive months during the past year, and less than 7 months of lower-extremity weight training were significantly associated with stress fracture incidence. Self-rated fair-poor fitness at baseline was the only variable significantly associated with other non-stress fracture overuse injury during basic training.

CONCLUSIONS

Among this sample of women, the risk of lower-extremity overuse injury was high, with a twofold risk of subsequent injury. The results suggest that stress fracture injury might be decreased if women entered training with high aerobic fitness and participated frequently in lower-extremity strength training. Furthermore, women reporting a history of menstrual irregularity at their initial medical exam may require closer observation during basic training.

Predictors of stress fracture susceptibility in young female recruits

BACKGROUND

Stress fractures account for substantial morbidity for young women undergoing U.S. Marine Corps basic training.

HYPOTHESIS

Certain pretraining characteristics identify women at increased risk of stress fractures during boot camp.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Data collected included baseline performance on a timed run (a measure of aerobic fitness), anthropometric measurements, and a baseline questionnaire highlighting exercise and menstrual status among 2962 women undergoing basic training at the Marine Corps Recruit Depot, Parris Island, in 1995 and 1996.

RESULTS

One hundred fifty-two recruits (5.1%) had 181 confirmed lower extremity stress fractures, with the most common sites being the tibia (25%), metatarsals (22%), pelvis (22%), and femur (20%). Logistic regression models revealed that having low aerobic fitness (a slower time on the timed run) and no menses during the past year were significantly associated with the occurrence of any stress fracture and with pelvic or femoral stress fracture during boot camp.

CONCLUSION

These findings suggest that stress fractures may be reduced if women entering Marine Corps Recruit Depot training participated in pretraining activities designed to improve aerobic fitness. Furthermore, women reporting no menses during the previous year may need additional observation during training.

CLINICAL RELEVANCE

Consistent with previous studies, we found that low aerobic fitness was the only modifiable risk factor associated with stress fractures during boot camp.

Running mileage, movement mileage, and fitness in male U.S. Navy recruits

PURPOSE

The purpose of this study was to determine whether there is a relationship between overall fitness improvement and varying amounts of running and movement mileage.

METHODS

Subjects were male U.S. Navy recruits (N = 1703, 25 divisions), ages 17-35 yr (mean age = 20.1 +/- 2.9 yr), who attended boot camp from April 1996 through August 1996. During the first week of training, recruits performed a 1.5-mile run to determine baseline fitness levels. The results from the initial run were compared with a final 1.5-mile run conducted 6 wk later.

RESULTS

Based on an age-adjusted fitness scale for a 1.5-mile run time, about one third of the recruits began recruit training in "Excellent-Superior" condition (N = 558), one third began in "Good" condition (N = 582), and one third began in "Poor-Fair" condition (N = 563). Running mileage among divisions ranged from 11.5 to 43.5 miles for the entire 7-wk training period (mean = 22.7 +/- 7.2 miles; 8-22 run days, mean = 13 +/- 4 d). In addition to running, the divisions accumulated many movement miles (110-202 miles; mean = 145 +/- 26 miles) while marching in formation. Recruits who began training in Poor-Fair condition improved the most with an average decrease in run time of 1:55 +/- 1:06 min (15.6% improvement). The Good group improved by 47 +/- 37 s (7.3% improvement), and the Excellent-Superior group improved by 17 +/- 32 s (2.9% improvement).

CONCLUSION

The magnitude of fitness improvement, as measured by run time improvement, was directly related to baseline fitness level but not related to movement mileage or high-intensity run mileage accrued during training.

Stress fracture in military recruits: gender differences in muscle and bone susceptibility factors

A total of 693 female U.S. Marine Corps recruits were studied with anthropometry and dual-energy X-ray absorptiometry (DXA) scans of the midthigh and distal third of the lower leg prior to a 12 week physical training program. In this group, 37 incident stress fracture cases were radiologically confirmed. Female data were compared with male data from an earlier study of 626 Marine recruits extended with additional cases for a total of 38 stress fracture cases. Using DXA data, bone structural geometry and cortical dimensions were derived at scan locations and muscle cross-sectional area was computed at the midthigh. Measurements were compared within gender between pooled fracture cases and controls after excluding subjects diagnosed with shin splints. In both genders, fracture cases were less physically fit, and had smaller thigh muscles compared with controls. After correction for height and weight, section moduli (Z) and bone strength indices (Z/bone length) of the femur and tibia were significantly smaller in fracture cases of both genders, but patterns differed. Female cases had thinner cortices and lower areal bone mineral density (BMD), whereas male cases had externally narrower bones but similar cortical thicknesses and areal BMDs compared with controls. In both genders, differences in fitness, muscle, and bone parameters suggest poor skeletal adaptation in fracture cases due to inadequate physical conditioning prior to training. To determine whether bone and muscle strength parameters differed between genders, all data were pooled and adjusted for height and weight. In both the tibia and femur, men had significantly larger section moduli and bone strength indices than women, although women had higher tibia but lower femur areal BMDs. Female bones, on average, were narrower and had thinner cortices (not significant in the femur, p = 0.07). Unlike the bone geometry differences, thigh muscle cross-sectional areas were virtually identical to those of the men, suggesting that the muscles of the women were not relatively weaker.

Gender differences in musculoskeletal injury rates: a function of symptom reporting?

PURPOSE

This study determined gender differences in voluntary reporting of lower extremity musculoskeletal injuries among U.S, Marine Corps (USMC) recruits, and it examined the association between these differences and the higher injury rates typically found among women trainees.

METHODS

Subjects were 176 male and 241 female enlisted USMC recruits who were followed prospectively through 11 wk (men) and 12 wk (women) of boot camp training. Reported injuries were measured by medical record reviews. Unreported injuries were determined by a questionnaire and a medical examination administered at the completion of training.

RESULTS

Among female recruits the most commonly reported injuries were patellofemoral syndrome (10.0% of subjects), ankle sprain (9.1%), and iliotibial band syndrome (5.8%); the most common unreported injuries were patellofemoral syndrome (2.1%), metatarsalgia (1.7%), and unspecified knee pain (1.7%). Among male recruits iliotibial band syndrome (4.0% of subjects), ankle sprain (2.8%), and Achilles tendinitis/bursitis (2.8%) were the most frequently reported injuries; shin splints (4.6%), iliotibial band syndrome (4.0%), and ankle sprain (2.8%) were the most common unreported diagnoses. Female recruits were more likely to have a reported injury than male recruits (44.0% vs 25.6%, relative risk (RR) = 1.72, 95% confidence interval (CI) 1.29-2.30), but they were less likely to have an unreported injury (11.6% vs 23.9%, RR = 0.49, 95% CI 0.31-0.75). When both reported and unreported injuries were measured, total injury rates were high for both sexes (53.5% women, 45.5% men, RR = 1.18, 95% CI 0.96-1.44), but the difference between the rates was not statistically significant.

CONCLUSIONS

Our results indicate that the higher injury rates often found in female military trainees may be explained by gender differences in symptom reporting.