Prevalence of Insomnia by Sex in U.S. Service Members: A Systematic Review and Meta-Analysis

Introduction: Insomnia is a significant yet underrecognized concern among U.S. service members (SMs), with broad implications for health, performance, and operational readiness. Prior prevalence estimates of insomnia vary widely, often because of inconsistent definitions, measurements, and study designs, which limits clear interpretation in the absence of pooled estimates. Sex-specific prevalence has also been reported in primary studies; however, findings remain mixed and inconclusive without pooled estimates. Branch-specific data are even more limited and can therefore only be synthesized descriptively. Unlike previous reviews, no meta-analysis has estimated insomnia prevalence solely on U.S. SMs and disaggregated by sex, leaving a critical gap in understanding within the military. Therefore, this systematic review and meta-analysis aimed to estimate the overall and sex-specific prevalence of insomnia in SMs and describe available data by service branch. Materials and Methods: This review followed PRISMA 2020 guidelines. PubMed, EMBASE, APA PsycINFO, and CINAHL were systematically searched for studies published between January 2016 and October 2024. Eligible studies reported insomnia prevalence in U.S. military populations. Meta-analyses were conducted in R using a random-effects model to account for between-study heterogeneity. Results: Eight studies met inclusion criteria, comprising 3 cohort and 5 cross-sectional designs, with insomnia sample sizes from 49 to 66,869 participants. The pooled prevalence of insomnia was 18% (95% CI, 0.11-0.29, P < .001, I^{2 =} 99.9%). Sensitivity analysis yielded a slightly higher prevalence of 23% (95% CI, 0.18-0.29, P < .001, I² = 99.9%). Sex-specific subgroup analysis revealed female SMs had higher odds of insomnia than males (OR = 2.05, 95% CI, 1.12-3.76, P < .001, I² = 98.7%), supported by sensitivity analysis (OR = 1.44, 95% CI, 1.36-1.54, P = .91, I² = 0%). Branch-specific meta-analysis was not feasible because of limited data. Conclusions: This review begins to address the gap by providing prevalence estimates of insomnia among SMs by narrowing wide-ranging prevalence estimates to a pooled range of 18-23% and demonstrating higher odds among females compared to males. Findings provide a more precise epidemiologic estimate and highlight the need for standardized insomnia measurement tools, expanded and consistent sex- and branch-specific research, and the incorporation of occupational and contextual factors. Addressing these gaps is critical to inform health planning and to support future sex- and branch-specific efforts to optimize readiness across the U.S. military.