Sleepless Nights, Unhealthy Hearts?

More worrisome news for people who toss and turn all night: Insomnia appears to be linked to a heightened risk for heart attack or stroke, a research review from China suggests.

"We found that difficulty initiating sleep, difficulty maintaining sleep, or non-restorative sleep were associated with 27 percent, 11 percent, and 18 percent higher risks of cardiovascular and stroke events, respectively," said study co-author Qiao He.

The reasons why aren't fully understood, said He, a graduate student at China Medical University in Shenyang.

However, the study doesn't establish a cause-and-effect relationship.

Sleep specialists say millions of Americans get too little sleep. "In modern society, more and more people complain of insomnia," He said.

Evidence of insomnia's harmful effects on overall health has accumulated in recent years.

"Previous studies have shown that insomnia may change metabolism and endocrine function, increase [nervous system] activation, raise blood pressure," He said. It also can spark a rise in levels of certain inflammation-related proteins. All of these are risk factors for heart disease and stroke, she explained.

For this report, the investigators looked at 15 studies that enlisted nearly 161,000 participants in all. The studies variously explored potential links between insomnia and a range of heart disease concerns, including heart attack, stroke and heart failure.

The association between insomnia and heart attack and stroke risk might even be slightly stronger among women. But that finding did not reach "statistical significance," He's team said in a news release from the European Society of Cardiology.

"However, we do know that women are more prone to insomnia because of differences in genetics, sex hormones, stress, and reaction to stress," said He. "It may therefore be prudent to pay more attention to women's sleep health."

She added that "health education is needed to increase public awareness of insomnia symptoms and the potential risks, so that people with sleep problems are encouraged to seek help."

The findings were published in the March 31 issue of the European Journal of Preventive Cardiology.