Sleep duration and cardiovascular disease gets lots of press, even though the studies are inconclusive. Some speculate a "U" shaped curve where too little sleep and too much sleep is associated with higher risk of cardiovascular disease. It's unclear, but insomnia gets linked to sleep deprivation, and thus the news runs with stories that insomnia can increase risk of cardiovascular disease. I have blogged about it multiple times, here, here, and here. There are relatively few studies that have examined the relationship between insomnia and stroke.
This study is a retrospective cohort study based in Taiwan. They looked at patients with a diagnosis of insomnia, and used a comparison group without insomnia. They excluded those patients with a known diagnosis of obstructive sleep apnea and those with previous diagnosis of stroke. Then they tracked the populations for 4 years to analyze the number of strokes that occurred. There were 21,438 subjects with insomnia diagnoses and 64,314 subjects without insomnia. As expected, prevalence of diabetes, high blood pressure, high cholesterol, depression, anxiety, and atrial fibrillation were all higher in the insomnia population. During the 4 year follow up period, 583 of the insomnia patients developed stroke, whereas 962 of the patients without insomnia developed stroke. The incidence rate was significantly higher in the insomnia patient group than in the group without insomnia.
Again, there are some important limitations in this study, some of which are not addressed by the study authors. One big one is that we really don't know if the patients had primary or secondary insomnia. For all we know, the patients with insomnia and stroke may all have had undiagnosed obstructive sleep apnea. Also, the researchers relied on a diagnosis code for insomnia, but that does not mean these patients had a clinical interview by a sleep physician to determine that diagnosis. We don't know who is making the diagnosis of insomnia or how it is being made. There seems to be too many details left out to make any reasonable conclusions. I do agree with the authors that we need to screen and treat insomnia. It's also important to make an accurate diagnosis.
The reason I harp on this topic is that many of my patients with chronic insomnia inadvertently worsen their insomnia by worrying about the supposed health effects of insomnia. The news media and magazine articles make "insomnia" sound so dangerous. But if these individuals have primary insomnia, then they are not necessarily at increased risk just from the insomnia alone.