An analysis of national data shows 53 percent of children ages 6 to 19 have been exposed to secondhand smoke. For children ages 6 to 11, even low levels of secondhand smoke were associated with more missed days of school, sleep disturbances, more wheezing and less physical activity.

“Adolescents may have more sporadic exposure (hanging with friends) compared to younger children who may be more chronically exposed at home,” study author Lara Akinbami of the National Center for Health Statistics in Hyattsville, Maryland, told Reuters. She noted other research has indicated that only smoking in one room of the house does not adequately protect children against secondhand smoke.

The findings are published in Academic Pediatrics.

A review of studies published last year found exposure to secondhand smoke increases the risk of wheezing and asthma in children and teens by at least 20 percent.