People exposed to passive smoking may have an increased risk of developing some form of dementia, a new study suggests.

According to UK and Chinese scientists, environmental tobacco smoke (ETS), more commonly known as passive or secondhand smoke, is already known to cause heart and lung diseases, including lung cancer. However until now, the potential impact of ETS on the development of dementia has not been studied in great detail.

The scientists decided to investigate this further. They interviewed almost 6,000 people over the age of 60, who lived in both rural and urban areas of China. The participants' smoking habits and rate of ETS exposure were assessed. Levels of dementia were also assessed.

The study found that one in 10 of the participants had a severe type of dementia and this appeared to be significantly related to their exposure to ETS.

"Passive smoking should be considered an important risk factor for severe dementia syndromes, as this study in China shows. Avoiding exposure to ETS may reduce the risk of severe dementia syndromes," said lead scientist, Dr Ruoling Chen of Anhui Medical University in China and King's College London.

He noted that currently, around 90% of the world's population live in countries without smoke-free public areas.

"More campaigns against tobacco exposure in the general population will help decrease the risk of severe dementia syndromes and reduce the dementia epidemic worldwide," Dr Chen added.

Details of these findings are published in the journal, Occupational and Environmental Medicine.

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