Non-smokers who are exposed to secondhand (passive) smoke have a 30% increased risk of suffering a stroke, a new study has found.

US researchers looked at almost 22,000 people aged 45 years and older. Of these, almost one in four were non-smokers who had been exposed to secondhand smoke in the last year.

Any strokes that took place between April 2003 and March 2012 were assessed. The vast majority of strokes that did occur were found to be ischaemic, i.e. due to a blockage of blood flow to the brain.

The study found that even after other stroke risk factors were taken into account, such as high blood pressure and heart disease, non-smokers exposed to secondhand smoke had a 30% increased risk of suffering a stroke than those not exposed to passive smoke.

"Our findings suggest the possibility for adverse health outcomes such as stroke among non-smokers exposed to secondhand smoke and add to the body of evidence supporting stricter smoking regulations," the researchers from South Carolina said.

Details of these findings are published in the American Journal of Preventive Medicine.