Difficulty in initiating sleep can increase the risk of cardiovascular and stroke events by as much as 27%, according to a new meta-analysis published in the European Journal of Preventive Cardiology.

Previous studies assessing the impact of insomnia or cardio-cerebral vascular events have used various definitions of the condition making it difficult to draw solid conclusions. The analysis in this study focused on links between cardio-cerebral vascular events and specific insomnia symptoms: difficulty initiating sleep (DIS), difficulty maintaining sleep (DMS), early morning awakening (EMA) and/or non-restorative sleep (NRS).

In total the researchers — based at China Medical Hospital, Shenyang, China — analyzed 15 prospective cohort studies from 13 different countries, which included 160,867 participants. The median follow up time ranged from 3 to 29.6 years. 

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The combined number of adverse events was 11,702. Analysis showed there were significant associations between sleep issues and the risk of heart disease and stroke; a relative risk increase of 1.27 for difficulty initiating sleep, 1.11 for difficulty maintaining sleep, and 1.18 for non-restorative sleep, all when compared to individuals who did not experience these insomnia symptoms. These numbers convert to increased cardiovascular and stroke event percentage risks of 27%, 11%, and 18%, for DIS, DMS, and NRS, respectively.

However, early morning awakening was not associated with any increase in cardio-cerebral vascular events. Overall the researchers found that the adverse risks were higher for females than males who had corresponding symptoms.

First author, Qiao He said, “We do know that women are more prone to insomnia because of differences in genetics, sex hormones, stress, and reaction to stress. It may therefore be prudent to pay more attention to women’s sleep health.”

The researchers acknowledge that the mechanism for the link between these symptoms and the adverse events is unknown. What is known from past literature is that insomnia may change metabolism, increase sympathetic activation, raise blood pressure, and elevate levels of proinflammatory and inflammatory cytokines – “All of which are risk factors for cardiovascular disease and stroke,” said He.

For more information visit Sagepub.com.