A new study published in the American Journal of Preventive Medicine found that secondhand smoke increases the risk of stroke by about 30 percent for non-smokers.

Using data from the Reasons for Geographic and Racial Differences in Stroke study, investigators found that even after adjustment for other stroke factors such as hypertension, diabetes, and heart disease, the 30 percent risk for non-smokers remained.

The current study included almost 22,000 participants with 23 percent reporting secondhand smoke exposure in the past year. From April 2003 to March 2012, 428 strokes were reported. A further analysis of the type of stroke (ischemic vs. hemorrhagic) was performed and showed that most strokes were due to blockage of blood flow to the brain (352 ischemic, 50 hemorrhagic, and 26 strokes of unknown sub-type).

Nearly 800,000 people in the U.S. suffer a stroke each year. Stroke is responsible for one out of every 19 deaths in the U.S. and it is a leading cause of disability.

The literature concerning adverse health effects of secondhand smoke is becoming clearer, although not all studies have replicated the association between secondhand exposure and stroke, said lead author Angela M. Malek, PhD, of the Department of Public Health Sciences, Medical University of South Carolina, Charleston, in a news release.

“Previous studies suffer from limitations in that few were prospective, adjustment for potential confounders has varied, stroke and SHS exposure have not been consistently defined, measurement and sources of SHS exposure have differed, stroke subtypes have not always been assessed, and some studies have been underpowered due to small sample size,” Malek said.

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