Smokers who have long been harangued about the medical consequences of their habit have a new one to ponder: It might be harming their sleep.

A new study by researchers at the Johns Hopkins School of Medicine found that smokers are four times as likely as nonsmokers to report trouble sleeping and feeling rested the next day. Measurements of brain activity showed that they aren't experiencing as much deep sleep during the night, a possible side effect of nicotine.

"Sleep has to be considered part of the problem," said Dr. Naresh M. Punjabi, the Hopkins pulmonologist who directed the study. "Physicians should not neglect sleep-related issues of smokers, especially sleep doctors."

The report, in this month's edition of the journal Chest, said that smokers spend more time in light sleep and less in deep sleep than nonsmokers. The result is a fitful night's sleep and drowsiness the next day.

A likely explanation is nicotine's effects on the brain, Punjabi said. A highly addictive ingredient of tobacco smoke, nicotine acts as a stimulant and can produce withdrawal symptoms within a few hours of a smoker's last puff.

As a result, a smoker can have more trouble falling asleep and reaching a stage of restful sleep. Then, just two to three hours later, the same person might begin nicotine withdrawal, compounding the problem.

"Some of the heaviest smokers will actually reach for a cigarette during the night when they wake up," Punjabi said. "Then, they may not be able to get back to sleep."

For the study, the researchers screened 6,441 volunteers taking part in a national study of cardiovascular health. The goal was to find a large group of healthy smokers - free of emphysema, lung cancer, diabetes, heart disease and other ills - who matched up demographically with an equal number of healthy nonsmokers.

Healthy smokers were so hard to find that the scientists eventually had to settle for a comparison of 40 smokers and 40 nonsmokers. The smokers puffed an average of 25 cigarettes per day.

The volunteers were outfitted at home with sleep-study equipment, including a device that continuously records brain activity.

The electroencephalograms (EEGs) showed that smokers on average had faster, higher-frequency brain waves throughout the night - indicating that they weren't experiencing as much deep sleep as nonsmokers.

"The kinds of EEG changes they saw are the kinds typically associated with poorer quality sleep," said Dr. Barbara Phillips, chairman of the sleep institute of the American College of Chest Physicians' Sleep Institute. The parent organization publishes Chest.

Deep sleep is "the stage where wounds heal, hormones are secreted, growth happens if it's going to happen - and it's the stage of sleep associated with muscle mass," Phillips said.

Dr. Jason Marx, director of the sleep disorders center at St. Joseph Medical Center in Towson, said he has heard smokers say they need a cigarette before bed to relax and wake up during the night needing another.

Punjabi suggested the "next frontier" will be to tailor nicotine replacement therapy - such as a patch - to smokers who are trying to quit and achieve a good night's sleep.

jonathan.bor@baltsun.com