New York: IANS) Chronic insomnia increases mortality risk primarily due to heart-related problems and not cancer, says a study led by an Indian-origin researcher.

People who suffer from persistent insomnia are also at greater risk of increased inflammation than those who experience intermittent insomnia, the findings showed.

"We hypothesised that insomnia that was persistent over eight years, rather than intermittent insomnia, was associated with death independent of the effects of sedatives, opportunity for sleep, and other confounding factors in a representative sample of the general adult community," explained lead investigator Sairam Parthasarathy, associate professor at the University of Arizona College of Medicine, Tucson.

"An enhanced understanding of the association between persistence of insomnia and death would inform treatment of the 'at-risk' population," Parthasarathy added.

Researchers found that after adjusting for various confounders such as age, sex, body weight, smoking, hypnotics and physical activity, people with persistent insomnia were 58 percent more likely to die during the study than those with no insomnia and that mortality was cardiovascular rather than cancer-related.

The study also determined that serum levels of C - reactive protein (CRP), an independent risk factor for mortality, was higher in people with persistent insomnia.

The investigators assessed the persistence of insomnia complaints in 1,409 adult participants.

The study commenced in 1972 with multiple follow-up surveys to 1996 and continuous mortality follow-up data to 2011 for a total of 38 years.

The study was published in The American Journal of Medicine.