Researchers followed 487,200 people in China for about a decade starting when they were 51 years old on average. None of them had a history of heart disease or stroke at the start of the study.
After almost a decade of follow-up, there were 130,032 cases of stroke, heart attack and other similar diseases.
Overall, people who had three insomnia symptoms - trouble falling or staying asleep, waking too early in the morning, and trouble staying focused during the day due to poor sleep - were 18% more likely to have events like a heart attack or stroke than people without any of these sleep issues, the researchers reported in Neurology.
"These results suggest that if we can target people who are having trouble sleeping with behavioral therapies, it's possible that we could reduce the number of cases of stroke, heart attack and other diseases later down the line," Dr. Liming Li, senior author of the study and a researcher at Peking University in Beijing, said in a statement.
About 11% of the people had difficulty falling asleep or staying asleep; 10% reported waking up too early; and 2% had trouble staying focused during the day due to poor sleep, the study found. The researchers didn't determine if the people met the full definition of insomnia.
Compared with participants without specific insomnia symptoms, those who did have sleep problems were older, more likely to be female, not married, and from rural areas. People with insomnia symptoms also less education, lower income, and were more likely to have a history of diabetes or mood disorders like anxiety or depression.
People who had trouble falling asleep or staying asleep were 9% more likely to have events like a heart attack or stroke than people who did not have this trouble.
And, people who woke up too early in the morning were 7% more likely to have these events than individuals without this issue.
When people had trouble staying focused during the day due to poor sleep, they were 13% more likely to experience events like a heart attack or stroke.
The increased risk of heart attack and stroke persisted even after researchers accounted for other factors that could independently affect the risk of stroke or heart disease like alcohol use, smoking, and level of physical activity.
"The link between insomnia symptoms and these diseases was even stronger in younger adults and people who did not have high blood pressure at the start of the study, so future research should look especially at early detection and interventions aimed at these groups," Li said.
The study wasn't a controlled experiment designed to prove whether or how insomnia symptoms might cause events like a heart attack or stroke. Another limitation is that researchers relied on participants to report their own sleep symptoms and any heart attacks or strokes they had.
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