Insomnia and risk of stroke
Several studies have linked sleep duration – both long and short – to cardiovascular disease. In contrast, few studies have investigated the relationship between insomnia and cardiovascular disease outcomes, such as risk for stroke. Moreover, the temporal relationship between insomnia and stroke has yet to be fully examined i.e. does insomnia precede and act as risk factor for the future onset of stroke?
In a recent study, published online in the journal Stroke, Ming-Ping Wu and colleagues conducted a four year prospective study examining whether insomnia acts as a risk factor for developing stroke, and whether persistence of insomnia enhances this risk. Approximately 85,000 adults were assessed as part of the Taiwan Longitudinal Health Insurance Database. Patients with insomnia were characterized according to physician codes from the International Classification of Diseases; those with a diagnosis of sleep apnea, previous stroke, and history of insomnia before study enrolment, were excluded. Persistent insomnia was defined as consistent insomnia diagnosis at each 180-day period across the four year interval; relapse of insomnia was defined as a return of insomnia after being diagnosed free of the condition for >180 days; and finally, insomnia remission was defined as transitioning to a noninsomnia diagnosis and remaining this way for remainder of the evaluation period. Hospitalization for stroke (and type of stroke) was recorded as the main dependent variable, and according to diagnostic codes from the International Classification of Diseases.
Over twenty-thousand participants met criteria for insomnia. Those in the insomnia group were nearly 85% more likely to have been hospitalized for stroke in the four year follow-up period. This increased risk was particularly pronounced for transient ischemic attack. When adjusting for potential confounding variables – including a range of physical and mental health conditions, as well as age, sex and socioeconomic status – those with insomnia still expressed a 54% increased risk of stroke relative to those without insomnia. Interestingly, those with a persistent pattern of insomnia also had a significantly higher cumulative incident rate of stroke, relative to those who initially experienced insomnia but subsequently went into remission. Thus severity and patterning of insomnia may play a role in stroke risk.
While mechanisms linking insomnia and stroke still remain to be elucidated, the authors note that increased inflammation and sympathetic nervous system activation, linked to sleep disturbance, may contribute to cardiometabolic deterioration. The research team conclude: “Our study provides population-based evidence that people with insomnia have higher incidences and risks of hospitalization for stroke as compared with noninsomniacs. The results of this study suggest that intervention to improve insomnia is needed and should be examined whether it could be a strategy to improve cardiovascular health.”
Ming-Ping, W., Huey-Juan, L., Shih-Feng, W., Chung-Han, H., Jhi-Joung, W., Ya-Wen, H. (2014). Insomnia subtypes and the subsequent risk of stroke. Stroke, published online 3 April, doi: 10.1161/STROKEAHA.113.003675