Researchers have determined that people in areas with high pollution are more likely to have sleep disorders, such as sleep apnea, according to the American Journal of Respiratory and Critical Care Medicine.
"To our knowledge, this is the first study to demonstrate a link between air pollution exposure and sleep-disordered breathing," wrote lead researcher Antonella Zanobetti in the report.
The study comes as the military reports skyrocketing rates of sleep apnea in recent years and as veterans groups see a connection between troops who have developed respiratory problems and sleep apnea and exposure to open-air burn pits in Iraq and Afghanistan.
Active-duty cases of obstructive sleep apnea – a condition that causes people to stop breathing as they sleep – have increased nearly 600 percent since 2000, with the biggest jumps coming a couple of years after the start of the wars in Iraq and Afghanistan. Military officials say part of the reason that the rates have increased may be because doctors have gotten better at diagnosing sleep apnea.
The new study, conducted by researchers at Brigham and Women's Hospital, and the Harvard School of Public Health, states that "the influence of air pollution on sleep-disordered breathing is poorly understood."
"Our hypothesis was that elevation in ambient air pollution would be associated with an increased risk of sleep-disordered breathing and nocturnal hypoxia, as well as with reduced sleep quality," researcher Antonella Zanobetti wrote in the report.
Zanobetti and her colleagues used data from the Sleep Heart Health Study, which included 6,000 people between 1995 and 1998, and compared it to air pollution data from the Environmental Protection Agency. They also looked at pollution in combination with temperature. It is 111 degrees in Baghdad today.
"We found novel evidence for pollution and temperature effects on sleep-disordered breathing," Zanobetti said. "Increases in apnea or hypopnea were associated with increases in short-term temperature over all seasons, and with increases in particle pollution levels in the summer months."
Hypopnea is shallow breathing. Apnea occurs when people actually stops breathing while sleeping, which usually causes them to wake up. The main symptom is daytime sleepiness.
The new study looked at levels of particulate matter, which, across Iraq and Afghanistan, have consistently been above acceptable EPA standards because of the burn pits and blowing dust. The military is conducting tests on particulate matter associated with sand to see if it can cause long-term health conditions.
Zanobetti wrote that particulate matter could cause sleep disorders by affecting the central nervous system as well as the upper airways of the lungs. She also noted that particulate matter has been shown to move from the nose up to the olfactory nerve in the brain, ultimately causing changes in neurotransmitter levels.
Previous studies have shown that dogs in polluted areas of Mexico City had more prefrontal lesions in the brain, inflammation in neurotransmitter levels, damage to the central nervous system, and embedded particulate matter. Children in polluted areas of Mexico City also had more prefrontal lesions, Zanobetti wrote.
"Pollution may increase sleep-disordered breathing through influencing central ventilatory control centers," she wrote. "Pollutants may directly contribute to nasal or pharyngeal inflammatory responses that increase upper airway resistance and reduce airway openness.