Longitudinal associations between insomnia symptoms and all-cause mortality among middle-aged and older adults: a population-based cohort study.

To date, there is no scientific consensus on whether insomnia symptoms increase mortality risk. We investigated longitudinal associations between time-varying insomnia symptoms (difficulty initiating sleep, difficulty maintaining sleep, early-morning awakening, and nonrestorative sleep) and all-cause mortality among middle-aged and older adults during 14 years of follow-up. Data were obtained from 2004 through 2018 survey waves of the Health and Retirement Study in the United States for a population-representative sample of 15 511 respondents who were ≥50 years old in 2004. Respondents were interviewed biennially and followed through the end of the 2018 survey wave for the outcome. Marginal structural discrete-time survival analyses were employed to account for time-varying confounding and selection bias. Of the 15 511 cohort respondents (mean [±SD] age at baseline, 63.7 [±10.2] years; 56.0% females), 5878 (31.9%) died during follow-up. At baseline (2004), 41.6% reported experiencing at least one insomnia symptom. Respondents who experienced one (HR = 1.11; 95% CI: 1.03-1.20), two (HR = 1.12; 95% CI: 1.01-1.23), three (HR = 1.15; 95% CI: 1.05-1.27), or four (HR = 1.32; 95% CI: 1.12-1.56) insomnia symptoms had on average a higher hazard of all-cause mortality, compared to those who were symptom-free. For each insomnia symptom, respondents who experienced difficulty initiating sleep (HR = 1.12; 95% CI: 1.02-1.22), early-morning awakening (HR = 1.09; 95% CI: 1.01-1.18), and nonrestorative sleep (HR = 1.17; 95% CI: 1.09-1.26), had a higher hazard of all-cause mortality compared to those not experiencing the symptom. The findings demonstrate significant associations between insomnia symptoms and all-cause mortality, both on a cumulative scale and independently, except for difficulty maintaining sleep. Further research should investigate the underlying mechanisms linking insomnia symptoms and mortality.