‘Second-hand smoke’ increases dementia risk

World Health Matters – China – by Gary Finnegan –  A study of nearly 6,000 people in five provinces in China has shown that people exposed to passive smoking have a significantly increased risk of several dementia syndromes.

Environmental tobacco smoke (ETS) has been shown to cause serious cardiovascular and respiratory diseases, including lung cancer and coronary heart disease. However, the impact of passive smoking on dementia has, until now, not been well studied.

Previous work has shown a link between ETS and cognitive impairment but the Chinese study is the first attempt to examine the link between second-hand smoke and dementia syndromes.

The research by scientists at Anhui Medical University in China in collaboration with researchers at King’s College London was published in Occupational and Environmental Medicine.

Dr Ruoling Chen, a visiting professor at Anhui Medical University and a senior lecturer in public health from King’s College London, led a team that interviewed 5,921 people aged over 60 in the rural and urban communities of Anhui, Guangdong, Heilongjiang, Shanghai and Shanxi to characterise their levels of ETS exposure, smoking habits and assess levels of dementia syndromes.

10% of the group had severe dementia syndromes, according to the research, and this was found to be significantly related to exposure level and duration of passive smoking. The associations with severe syndromes were found in people who had never smoked and in former and current smokers.

The data from the Anhui cohort, which were collected at baseline in 2001-03 for dementia syndromes and in the follow up in 2007-08 for ETS exposure and dementia, further excluded the possibility that dementia syndromes caused people to be more exposed to environmental tobacco smoke.

“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,” Dr Chen said.

China now has a large ageing population which has the potential to place a major burden on families and the health system.

A separate recent paper by Chen and colleagues highlighted the links between passive smoking and Alzheimer’s disease. This too highlights the need for public health measures to protect people from ETS, he said.

“At present, we know that about 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.”

China, the world’s most populous nation, is the largest consumer of tobacco in the world, with 350 million smokers. Since 2006, the Chinese government has actively promoted the introduction of smoke-free environments in hospitals, schools, on public transport and in other public places, but implementation has not been widespread.

Recent data show that the prevalence of passive smoking is still high, with over 50% of people exposed to ETS on a daily basis. China also has the highest number of dementia sufferers in the world, with increasing rates of new cases as the population ages.