The prevalence and incidence of sleep disorder symptoms, correlates, and sex-stratified longitudinal associations with mental and menstrual health outcomes in UK Service Personnel: a prospective survey-based cohort study protocol.

STUDY OBJECTIVES: Sleep disturbance is highly prevalent in military populations, associated with adverse mental health, physiological, and operational outcomes. However, the epidemiology and longitudinal course of sleep disturbances among UK Armed Forces personnel remain unknown. Emerging evidence suggests that sleep disturbance may act as an upstream vulnerability factor for mental health disorders, with additional links to broader outcomes such as menstrual dysfunction in women. Prospective data in UK military populations are scant. This study aims to quantify the prevalence, incidence, and longitudinal associations between sleep disorder symptoms, mental health, and menstrual health outcomes in UK service personnel. The study aims to further investigate demographic and service-related moderators and explore potential mediating pathways underlying these relationships. METHODS: This prospective, survey-based cohort study will aim to recruit ~n 1316 Regular and n 1387 Reserve UK Armed Forces personnel, stratified by military service branch (Army, Royal Navy, Royal Air Force) and sex (male and female). Participants will complete validated self-report measures of sleep, mental health (e.g. PTSD, depression, anxiety, nightmares, suicidal ideation) combat exposure, and menstrual health (women only) at baseline, 6, 12, and 24 months. Participants will also undertake a 14-day sleep monitoring protocol using wrist-worn actigraphy and consensus sleep diaries to derive objective and subjective sleep-wake indices. Analyses will aim to assess prevalence, incidence and chronicity of sleep disturbances, along with multivariable regression and longitudinal mixed-effects models to examine associations with mental health outcomes and potential moderating factors. Longitudinal mediation analyses (four models) will determine potential mechanisms linking sleep disturbance with adverse health outcomes. RESULTS: This protocol describes the study design and planned analyses. CONCLUSIONS: This study will provide the first comprehensive longitudinal assessment of sleep disturbance and its associations with mental and menstrual health in UK Armed Forces personnel. Findings will inform targeted interventions, including behavioural sleep strategies, and support evidence-based policy and practice within UK Defence.