Researchers say that individuals exposed to passive smoking are at a significantly increased risk for severe dementia syndromes.
Ruoling Chen (King's College of London, UK) and co-authors say that environmental tobacco smoke (ETS) exposure should be considered an important risk factor for severe dementia syndromes and that avoidance of ETS may reduce the rates of severe dementia worldwide.
"At present, we know that about 90% of the world's population live in countries without smoke-free public areas," Chen remarked in a press statement. "More campaigns against tobacco exposure in the general population will help decrease the risk of severe dementia syndromes and reduce the dementia epidemic worldwide."
Lack of research has led to uncertainty surrounding the relationship between ETS and dementia, say the authors. They say the current study is the first to reveal a significant link between ETS and dementia, as opposed to just cognitive impairment.
As reported in Occupational and Environmental Medicine, Chen et al interviewed 5921 people aged 60 years or over from five provinces in China and found that 626 (10.6%) of them had severe dementia syndromes, while 869 (14.7%) had moderate syndromes.
Dementia was assessed using the Automated Geriatric Examination for Computer Assisted Taxonomy on a scoring system of 1-5, where a score of 3-5 was classified as a severe dementia syndrome and a score of 1-2 as a moderate dementia syndrome.
Individuals exposed to passive smoking had a significant 29% increased risk for severe dementia. After adjusting for age, severe dementia was dose-dependently related to exposure level and duration, the authors note.
The cumulative exposure dose data showed an adjusted relative risk of 0.99 for severe dementia for more than 0 to 24 level years of exposure, 1.15 for 25-49 level years, and 1.18 for 59-74 level years, compared with no exposure. The relative risk was 1.39 for 75-99 level years of ETS and 1.95 for 100 level years or more.
Significant associations between ETS and dementia were observed in never smokers and former/current smokers. The authors say that their findings excluded the possibility that dementia syndromes caused people to be more exposed to environmental tobacco smoke.
There were no positive associations between ETS and moderate dementia syndromes.
"China, along with many other countries, now has a significantly aging population, so dementia has a significant impact not only on the patients but on their families and carers. It's a huge burden on society," said Chen.
"The increased risk of severe dementia syndromes in those exposed to passive smoking is similar to increased risk of coronary heart disease - suggesting that urgent preventive measures should be taken, not just in China but many other countries."
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