A new study
in China is the first to show a significant link between second-hand smoke and dementia. So-called passive smoking, inhaling other people's cigarette smoke, is already known to cause heart disease and lung cancer.
China is the world's largest consumer of tobacco, with 350 million smokers. It also has the most dementia sufferers, a number that is growing rapidly as the population ages.
Researchers from King's College London and Anhui Medical University interviewed nearly 6,000 people over age 60 in five Chinese provinces, to assess their smoking habits, exposure to cigarette smoke, and level of dementia. They found 10 percent had severe dementia.
Lead author, Dr. Ruoling Chen, said this study highlights the need to protect people from environmental tobacco smoke.
The World Health Organization says only 11 percent of the world's population lives in countries with laws that create smoke-free public places. Chinese government efforts to promote such environments have met with limited success.
The new report is published in Occupational and Environmental Medicine.