Passive smoking increases a person's risk of dementia and other forms of cognitive problems, British and US researchers have said.
The report, published in the British Medical Journal on Friday, found a 44 percent increased risk for passive smoking.
"Our results suggest that inhaling other people's smoke may damage the brain, impair cognitive functions such as memory, and make dementia more likely," said David Llewellyn of Britain's University of Cambridge, who led the study.
Earlier research proved that passive smoking leads to lung cancer and heart disease. The World Health Organization (WHO) says that more than half of children in the world inhale second-hand smoke in their homes.
Previous studies had linked smoking during pregnancy with an increased risk of miscarriage and birth defects.
Smoking can also increase the risk of developing diabetes, one of the main causes of morbidity and mortality in the world, by seven percent.