Researchers whose work appeared in the journal Addiction Biology found that of nearly 1,100 smokers surveyed, 17 percent got fewer than six hours of sleep each night and 28 percent reported "disturbed" sleep quality.

That compared with rates of seven percent and 19 percent respectively among more than 1,200 non-smokers who were also surveyed, said lead researcher Stefan Cohrs, of Charite Berlin medical school in Germany.

"This study demonstrates for the first time an elevated prevalence of sleep disturbance in smokers compared with non-smokers in a population without lifetime history of psychiatric disorders even after controlling for potentially relevant risk factors," Cohrs and his colleagues wrote.

The findings cannot prove that smoking directly impairs sleep, since smokers may have other habits that could affect their shut-eye such as staying up late to watch TV or getting little exercise, Cohrs told Reuters Health in an email.

But there is also reason to believe the stimulating effects of nicotine may be to blame.

"If you smoke and you do suffer from sleep problems, it is another good reason to quit smoking," Cohrs said.

Poor sleep quality may not only make your waking hours tougher. Some studies have also linked habitually poor sleep to health problems like obesity, diabetes and heart disease.

The study included 1,071 smokers and 1,243 non-smokers who were free of mental health disorders, since those conditions may make a person both more likely to smoke and more vulnerable to sleep problems.

The researchers used a questionnaire that gauges sleep quality. Overall, more than one-quarter of smokers had a score than landed them in the category of "disturbed" sleep, meaning they had a high probability of insomnia.

Many things can affect sleep quality, and Cohrs's team was able to account for factors such as age, weight, and alcohol abuse. Yet smoking was still linked to poorer sleep quality.

It's still possible there are other things about smokers that impair their sleep, but Cohrs said he thinks the most likely culprit is nicotine - and the prospect of better sleep could provide smokers with an additional reason to quit. SOURCE: bit.ly/TOrYk0

(Reporting from New York by Amy Norton at Reuters Health; editing by Elaine Lies)

• A Permanent Economic Emergency