Smoking linked to higher dementia risk

Smokers have a higher risk of developingdementia, but giving up smoking can lower that risk, according to a new study in South Korea.

Long-term quitters and those who had never smoked had 14 per cent and 19per cent lower risks for dementia, respectively, compared tosmokers who kept up with the habit, the study authors reportedin the Annals of Clinical and Translational Neurology.

"Smoking is well known for its thousands of negative healthconsequences, including cancers and cardiovascular diseases.However, its impact on our brain is relatively less emphasized,"said lead study author Dr. Daein Choi of the Seoul NationalUniversity College of Medicine.

The article cites several case-control studies from the1980s and 1990s that found smoking reduced the risk of Alzheimer's disease, but these studies were typically funded bytobacco companies.

"There has been a misconception that the stimulant effect ofnicotine might act as a protective factor for dementia," Choitold Reuters by email.

Smoking and Alzheimer's risk

Choi and colleagues studied health claims from a nationaldatabase in Korea, focusing on 46,000 men over age 60. Based onquestionnaire responses, the researchers classified the menas continual smokers, short-term quitters of less than fouryears, long-term quitters of four years or more, and neversmokers.

From the start of the study in 2002 until the end in 2013,1,644 men were diagnosed with dementia.

Compared to continual smokers, long-term quitters and neversmokers had a lower risk of dementia in general, and also adecreased risk of so-called vascular dementia, which is causedby poor blood flow to the brain. Never smokers also had a lowerrisk of Alzheimer's disease.

"The interesting point is that the increased risk ofdementia related to smoking was reversible through smoking cessation," Choi said. "We would encourage smokers to quit tobenefit from a reduced risk of dementia."

A limitation of the study is that it may not have been longenough to fully determine the effects of smoking cessation on
Alzheimer's disease, which starts slowly and worsens over time.Plus, smoking habits may have changed after the questionnaireswere returned.

Quit to 'prevent or slow' dementia

Janine Cataldo of the University of San Francisco Center forTobacco Control Research and Education, who wasn't involved inthis study, told Reuters, "Smoking cessation could be avaluable and feasible intervention to prevent or slow theprogression of dementia."

In a study published in 2010, Cataldo and colleaguesreviewed previous research publications and found that smokers were almost two times more likely than non-smokers to developAlzheimer's disease.

"The myth that smoking protects against Alzheimer's diseasemay discourage cessation attempts among older smokers andcontribute to the reluctance of health care providers to treattobacco dependence in older smokers," she said by
email.

Additional studies should look at smoking cessation anddementia across different ethnicities, as well as with women,
Cataldo said.

"Given that smoking is a significant risk factor forcardiovascular disease and Alzheimer's disease, it makes sense that smoking cessation could become an integral part of theprevention and treatment of Alzheimer's disease," she said.