The study followed 54,279 people between the ages of 20-89 for an average of more than 11 years, and found that those who suffered from three symptoms of insomnia had a more than three-fold increased risk of developing heart failure compared to those with no insomnia symptoms.
Dr Lars Laugsand, a post-doctoral fellow in the Department of Public Health, Norwegian University of Science and Technology, Trondheim, Norway, said: "We related heart failure risk to three major insomnia symptoms including trouble falling asleep, problems staying asleep, and not waking up feeling refreshed in the morning.
In our study, we found that persons suffering from insomnia have increased risk of having heart failure. Those reporting suffering from all three insomnia symptoms simultaneously were at considerably higher risk than those who had no symptoms or only one or two symptoms."
However, he stressed that although the study shows that insomnia is linked to an increased risk of heart failure, it does not show that it causes it.
Dr Laugsand and his colleagues collected data from men and women enrolled in the Nord-Trondelag Health study (HUNT) between 1995 and 1997 and who were free from heart failure when they joined. Heart failure is a condition in which the heart is unable to pump enough blood around the body at the right pressure. It usually occurs because the heart muscle has become too weak or stiff to work properly. The researchers followed the study participants until 2008, by which time there had been a total of 1412 cases of heart failure.
When participants joined the study they were asked whether they had difficulty going to sleep and staying asleep, with the possible answers being "never", "occasionally", "often" and "almost every night". They were also asked how often they woke up in the morning not feeling refreshed (non-restorative sleep): "never, few times a year", "one to two times per month", "once a week", "more than once a week".
After adjusting for factors that could affect the results, such as age, sex, marital status, education, shift work, blood pressure, cholesterol, diabetes, body mass index, physical activity, smoking, alcohol, any previous heart attack, depression and anxiety, the researchers found that having difficulties going to sleep and staying asleep almost every night, and having non-restorative sleep more than once a week were associated with an increased risk of heart failure when compared with people who never or rarely suffered from these symptoms.
When they looked at the number of symptoms, the researchers found a statistically significant three-fold (353 percent) increased risk of heart failure for people who had all three insomnia symptoms, compared to those with none, after adjusting for most confounding factors apart from depression and anxiety.
When they adjusted their findings to include depression and anxiety, the risk was still significant, with a slightly more than four-fold risk (425 percent) of heart failure.
The study was recently published in the European Heart Journal.