Children with asthma may have a harder time getting a good night's sleep if they live with a smoker.
Researchers found that of more than 200 6- to 12-year-olds with asthma, those exposed to secondhand smoke tended to have poorer sleep at night and more drowsiness during the day.
While the reasons for the connection are uncertain, the researchers say it's likely that asthmatic children exposed to tobacco smoke have more nighttime breathing problems, which in turn disrupts their sleep.
The link between secondhand smoke and sleep problems was still apparent when the researchers accounted for the severity of the children's asthma overall -- suggesting that exposure to smoking, itself, was affecting the children's quality of sleep.
Parents already have many reasons not to smoke, particularly if their children have asthma. These latest findings offer more incentive, according to lead researcher Dr. Kimberly Yolton, an assistant professor of pediatrics at Cincinnati Children's Hospital Medical Center in Ohio.
"Children with asthma are especially vulnerable to the effects of tobacco smoke exposure," Yolton told Reuters Health in an email.
"In addition to exacerbating the respiratory problems associated with asthma," she said, "we now are able to present evidence that this exposure may be a cause for increased sleep disturbances among children with asthma."
Yolton pointed out that childhood sleep disturbances can have significant consequences, including attention and behavior problems, and poorer school performance. So it is "highly likely," she said, that secondhand smoke indirectly feeds these problems in some children with asthma.
The findings, reported in the latest issue of the journal Pediatrics, are based on assessments of 219 Cincinnati-area children with asthma. Parents were interviewed about their children's sleep habits, asthma severity and exposure to secondhand smoke at home and elsewhere.
The researchers also took blood samples from the children to measure levels of cotinine -- a byproduct of nicotine that serves as a marker of exposure to tobacco smoke.
Yolton's team found that, surprisingly, nearly all of the children in the study -- 93 percent -- had relatively high scores on a standard measure of sleep problems. High enough, in fact, to suggest "clinically relevant" sleep disorders.
But children exposed to secondhand smoke had generally poorer sleep than their peers who were unexposed. That included more difficulty falling asleep, more nighttime breathing symptoms and more so-called parasomnias -- problems such as sleepwalking, nightmares and night "terrors."
Along with the effects of tobacco smoke on children's airways, there is also a possible role for nicotine -- a known stimulant that may affect sleep patterns, according to Yolton and her colleagues.
The bottom line, she said, is that this is "just one more reason that parents should refrain from smoking around their children with asthma."
Yolton added that, while the study did not include children without asthma, it is likely that secondhand smoke could disturb their sleep as well.
SOURCE: Pediatrics, February 2010.