Associations of Insomnia Symptoms and Trajectories with Incident Cardiovascular Disease: A Population-Based Cohort Study

Background There is limited understanding regarding associations between insomnia symptoms, particularly the trajectories of insomnia symptoms, and cardiovascular disease (CVD). We aimed to investigate the associations of insomnia symptoms and trajectories with the risk of incident CVD. Methods This study used data from the Health and Retirement Study. Insomnia symptoms included non-restorative sleep, difficulty initiating sleep, early morning awakening, and difficulty maintaining sleep, classified on a scale ranging from 0 to 8. We also identified four distinct trajectories of insomnia symptoms: low, decreasing, increasing, and high insomnia symptoms. Examined outcomes included incident heart disease, stroke, and the combination of the two referred as CVD in the present study. Cox proportional hazard models were used to calculate the hazard ratio (HR) and 95% confidence interval (95% CI) after adjusting for potential confounders. Results A total of 12 102 participants aged 50 years or over without CVD at baseline were included. During a median follow-up of 10.2 years, 3 962 first CVD events occurred (3 372 heart disease and 1 200 stroke). Participants experiencing one (HR, 1.16 [95% CI, 1.05-1.27]), two (HR, 1.16 [ 95% CI, 1.05-1.28]), or three to four (HR, 1.26 [95% CI, 1.15-1.38]) insomnia symptoms had a higher risk of incident CVD compared to those not experiencing any insomnia symptoms. After a median follow-up of 8.4 years after the visit 2, 2 375 first CVD events occurred (1 981 heart disease and 705 stroke). Using the trajectory with low insomnia symptoms as the reference, increasing insomnia symptoms (HR, 1.28 [95% CI, 1.10-1.50]) and high insomnia symptoms (HR, 1.32 [95% CI, 1.15-1.50]) were associated with an increased risk of incident CVD. Conclusions Higher insomnia symptoms and increasing insomnia symptoms over time are associated with a higher risk of CVD in the community. Public health awareness and screening for insomnia symptoms in the middle-aged and elderly population should be encouraged to reduce CVD. Keywords Cardiovascular disease; Insomnia symptoms; Trajectory; Cohort study