Association Between Insomnia Symptoms and Trajectory With the Risk of Stroke in the Health and Retirement Study

Background and Objectives: Insomnia is a common condition affecting over a third of the United States population. However, the link between insomnia symptoms and stroke is understudied and the underlying mechanism remains unclear. This study aimed to investigate the relationship between insomnia symptoms and the incidence of stroke.

Methods: The Health and Retirement Study, a survey of Americans older than 50 years and their spouses, from 2002 to 2020 was used as the data source. Only those who were stroke-free at baseline were included in the present study. The exposure variable was insomnia symptoms and was derived from self-reported sleep-related factors including difficulty initiating sleep, difficulty maintaining sleep, waking up too early, and nonrestorative sleep. Repeated measures latent class analysis was used to identify insomnia trajectories over time. To investigate the relationship between insomnia symptoms and stroke events reported during the follow-up period, cox proportional hazards regression models were employed. Mediation analyses of comorbidities were performed utilizing causal mediation within a counterfactual framework.

Results: A total of 31,126 participants were included with a mean follow-up of 9 years. The mean age was 61 years (SD=11.1) and 57% were female. Insomnia symptom trajectories remained constant over time. Compared to subjects with no insomnia symptoms, an increased risk of stroke was observed for those with insomnia symptom scores ranging from 1 to 4 and 5 to 8 (hazard ratio (HR) = 1.16, 95% confidence interval (CI): 1.02, 1.33) and (HR =1.51, 95% CI: 1.29, 1.77), respectively indicating a dose-response relationship. The association was stronger in participants aged less than 50 years (HR=3.84, 95% CI: 1.50, 9.85) than those 50 years and above (HR=1.38, 95% CI: 1.18, 1.62) comparing those with insomnia symptoms ranging from 5 to 8 to those with no insomnia symptoms. This association was mediated by diabetes, hypertension, heart disease, and depression.

Discussion: Insomnia symptoms were associated with an increased risk of stroke, especially in adults younger than 50 years, and the risk was mediated by certain comorbidities. Increased awareness and management of insomnia symptoms may contribute to the prevention of stroke occurrence.