Air pollution has long been known to have a negative effect on health, says researcher Antonella Zanobetti, PhD, a senior research scientist at the Harvard School of Public Health. "With this study, we found air pollution also increases the risk of poor sleep," she says.
More specifically, air pollution increased the risk of sleep-disordered breathing, a group of disorders including sleep apnea, in which breathing stops briefly during sleep. Up to 17% of U.S. adults have sleep-disordered breathing, Zanobetti says, although many are unaware they have the problem.
Sleep-disordered breathing and air pollution have both been linked to increased risk for cardiovascular disease, but the link between air pollution and sleep disordered breathing is not well understood, Zanobetti says. Her study is believed to be the first to link pollution and breathing problems during sleep.
The study is published online in the American Journal of Respiratory and Critical Care Medicine.
Zanobetti and colleagues used data from the Sleep Heart Health Study, which included more than 6,000 participants and looked at the cardiovascular effects of sleep-disordered breathing. From that study, conducted between 1995 and 1998, the researchers evaluated more than 3,000 of the participants for the air pollution study.
They also got data on air pollution monitoring from seven cities: Framingham, Mass., Minneapolis, Minn., New York, Phoenix, Pittsburgh, Sacramento, Calif., and Tucson, Ariz.
Participants were monitored during sleep to evaluate sleep problems and oxygen saturation of the blood, among other parameters.
The experts speculated that an increase in air pollution would be linked with an increased risk of sleep-disordered breathing, low blood oxygen levels, and reduced quality of sleep. They looked at the interaction of seasons with the level of air pollution commonly associated with traffic. They also looked at whether seasonal temperature variations would have an effect, independently, on sleep problems.
They controlled for such factors known to be linked with sleep-disordered breathing, such as advancing age and smoking.
Affects of Air Pollution and Temperature Changes
As air pollution and temperature increased, so did breathing problems during sleep, says Diane Gold, MD, MPH, associate professor of environmental health, Harvard School of Public Health, and another researcher on the study.