The risk of stroke may be much higher in patients with insomnia, compared with people who do not have trouble sleeping, according to research published online ahead of print April 3 in Stroke. The risk of stroke may be greater for individuals who have insomnia during young adulthood, compared with people who have insomnia later on.
“To our knowledge, this is the first study to indicate that individuals with remission insomnia, relapse insomnia, and persistent insomnia subtypes have greater risks of developing stroke as compared with the control group,” said lead author Ming-Ping Wu, MD, PhD, of the Department of Obstetrics and Gynecology at Chi-Mei Medical Center in Tainan, Taiwan. When the investigators analyzed the results according to stroke type, they found that the ratio of the incidence of stroke in patients with insomnia to that in people without insomnia was highest for transient ischemic attack. The ratios were successively lower for unspecified stroke, ischemia, and hemorrhage.
An Analysis of Medical Data From Taiwan
Dr. Wu and colleagues conducted a retrospective cohort study using outpatient and inpatient claims filed between January 2002 and December 2005 that were included in Taiwan’s Longitudinal Health Insurance Database 2000. Eligible participants in the case group had one or more single hospitalization with a diagnosis code for insomnia or three or more outpatient visits with a diagnosis code for insomnia within the same year.
The investigators assembled a comparison group by matching each patient in the case group with three individuals without insomnia according to sex, age, and enrollment date. Patients with sleep apnea, previous diagnosis of stroke, and previous diagnosis of insomnia before enrollment were excluded from the case and control groups. Each participant was followed for four years from his or her index enrollment date until death or the end of follow-up.
Dr. Wu and colleagues evaluated differences in demographics and comorbidities between patients with and without insomnia using c2 tests. They used log-linear Poisson regression to calculate incidence rate ratios (IRRs) of stroke to compare the rate in patients with insomnia with that in patients without insomnia. Kaplan–Meier curves enabled the researchers to plot and compare the cumulative risk of hospitalization for stroke between patients with and without insomnia, and Cox proportional hazards regressions were applied to estimate the effect of insomnia on the risk of stroke.
Diabetes May Increase Stroke Risk Among Patients With Insomnia
The investigators included 21,438 subjects with insomnia and 64,314 matched participants without insomnia in their analysis. The mean age was 52 among patients with insomnia and 51 among controls. The prevalence of each comorbidity (eg, diabetes, hypertension, and depression) was higher in participants with insomnia than in those without.
During the four-year follow-up period, 583 patients with insomnia and 962 patients without insomnia were admitted to the hospital with stroke. The incidence rate of stroke was significantly higher (IRR, 1.85) in patients with insomnia than in controls. The IRR for each stroke subtype was higher in patients with insomnia, compared with patients without insomnia. The ratios were as follows: ischemia (IRR, 1.79), transient ischemic attack (IRR, 2.84), hemorrhage (IRR, 1.32), and unspecified stroke (IRR, 2.07). The incidence rate of stroke was higher for individuals with insomnia than for controls regardless of age and gender.
The case-to-control IRR for stroke decreased as age increased. The investigators found the largest IRR for stroke among participants ages 18 to 34 (IRR, 8.06). Except for diabetes, comorbidities did not significantly affect the risk of stroke. Among individuals with diabetes, patients with insomnia had a greater risk of stroke than those without insomnia.
Cox regression analyses indicated that risk of stroke was increased by 54% among individuals with insomnia, compared with controls, after adjusting for all other covariates. Compared with controls, crude hazard ratio for stroke was 2.04 among patients with persistent insomnia, 1.76 among patients with a relapse of insomnia, and 1.55 among participants with remission of insomnia, in unadjusted analysis. After the researchers adjusted for other relevant covariates, these hazard ratios became similar among the three insomnia subtypes.
Sleep Deprivation May Affect Cardiovascular Health
Proposed pathophysiologic mechanisms linking sleep duration and the cardiovascular system may explain how insomnia predisposes an individual to stroke. “Sleep deprivation and insomnia symptoms may alter cardiovascular health through inflammation, endocrine or metabolic dysregulation, and increased sympathetic nervous activity,” said the authors. “Clinical studies suggested that sleep deprivation may affect levels of cytokines known to play a role in regulating systematic inflammation.… Further investigations should be conducted to explore whether short sleep and prolonged sleep may trigger different biologic mechanisms contributing to cardiometabolic deterioration.”