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Heavy Smoking in Midlife May Be Associated with Dementia in Later Years October 25, 2010
Heavy smoking in middle age appears to be associated
with more than double the risk for Alzheimer's disease and other forms of
dementia two decades later, according to a report posted online today that
will be published in the February 28 print issue of Archives of
Internal Medicine, one of the JAMA/Archives journals. Current
estimates suggest smoking is responsible for several million deaths per
year from causes such as heart disease and cancer, according to background
information in the article. Although smoking increases risks of most
diseases and of death, some studies have shown a reduced risk of
Parkinson's disease and other neurodegenerative conditions among smokers.
"The link between smoking and risk of Alzheimer's disease, the most
common subtype of dementia, has been somewhat controversial, with some
studies suggesting that smoking reduces the risk of cognitive
impairment," the authors write. Minna
Rusanen, M.D., of A
total of 5,367 participants (25.4 percent) were diagnosed with dementia
during an average of 23 years of follow-up, including 1,136 with
Alzheimer's disease and 416 with vascular dementia. Those who smoked more
than two packs per day in middle age had an elevated risk of dementia
overall and also of each subtype, Alzheimer's disease and vascular
dementia, compared with non-smokers. Former smokers, or those who smoked
less than half a pack per day, did not appear to be at increased risk. Associations
between smoking and dementia did not vary by race or sex. Smoking is a
well-established risk factor for stroke, and may contribute to the risk of
vascular dementia through similar mechanisms, the authors note. In
addition, smoking contributes to oxidative stress and inflammation,
believed to be important in the development of Alzheimer's disease.
"It is possible that smoking affects the development of dementia via
vascular and neurodegenerative pathways," the authors write. "To
our knowledge, this is the first study evaluating the amount of midlife
smoking on long-term risk of dementia and dementia subtypes in a large
multiethnic cohort," they conclude. "Our study suggests that
heavy smoking in middle age increases the risk of both Alzheimer's disease
and vascular dementia for men and women across different race groups. The
large detrimental impact that smoking already has on public health has the
potential to become even greater as the population worldwide ages and
dementia prevalence increases." More Information on US Health Issues
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