Are there sex differences in the influence of insomnia symptoms and sleep duration on the trajectory of neuromuscular strength decline?

INTRODUCTION: A few longitudinal studies investigating the effect of sleep problems on the decline in neuromuscular strength (NMS) have produced conflicting results. OBJECTIVE: To examine sex differences in how insomnia symptoms (IS) and sleep duration (SD) affect the trajectory of NMS decline. METHODS: A longitudinal study with an eight-year follow-up period was conducted involving 6429 participants from the English Longitudinal Study of Ageing (ELSA) aged 50 or older. Participants with grip strength ≥27 kg for men and ≥16 kg for women were included. IS were investigated using a questionnaire adapted from Jenkins. SD was classified as short (≤6 h), ideal (>6 to <9 h), and long (≥9 h). Grip strength was the outcome. Generalised linear mixed models, stratified by sex and adjusted for sociodemographic, behavioural, clinical, and anthropometric variables, were used to estimate rates of NMS decline as a function of IS and SD. RESULTS: While an increase in IS was linked to a greater NMS decline rate in men (-0.02 kg per year; 95% CI: -0.04 to -0.01), women with SD ≥9 h experienced a higher rate of decline (-0.14 kg per year; 95% CI: -0.26 to -0.03). CONCLUSION: Sex differences were observed in the influence of sleep problems on the rate of NMS decline. Insomnia has a greater effect on men, whereas longer SD affects women more.