The analysis, which considered more than 54,000 men and women, linked insomnia symptoms and heart failure, even in people who had never had a heart problem. The study does not show cause and effect, though.
"If subsequent studies confirm our findings and if causality is better established, the observed ... association between insomnia and [heart failure] risk could have implications for cardiovascular prevention, since insomnia is an easily recognizable and potentially manageable condition," the researchers write.
Lars E. Laugsand, MD, says the findings do not have immediate implications for doctors and patients, beyond the fact that sleep is important to good health.
But, he says, the chronic stress responses seen in insomnia could be expected to have an impact on the heart. "Patients who are stressed both at night and during the day have increased blood pressure, increased release of stress hormones, increased heart rate, etc., and all of these factors are related to heart failure, so that's a potential link."
More Insomnia, More Risk
The researchers reviewed data relating to insomnia symptoms from 54,279 people between 1995 and 1997, none of whom had heart failure at the beginning of the study. By 2008, more than 1,400 people had developed heart failure.
After taking into account different factors, such as age, heart disease risk, or psychological factors, insomnia symptoms remained strongly linked with heart failure, with more symptoms linked with higher risk.
For example, people who reported having "difficulty initiating sleep" on "almost every night" had a 27% to 66% greater risk of developing heart failure compared with people with no insomnia symptoms. By contrast, those who reported "difficulty initiating sleep" on a frequent basis, in addition to "difficulty maintaining sleep" and feeling that their sleep was "non-restorative," had a risk of heart failure that ranged from two to five times higher than in people with no insomnia symptoms.
The next step, Laugsand says, would be a study treating patients for insomnia to see whether such a strategy could lessen the development of heart failure.