MONDAY, Oct. 25 (HealthDay News) -- Heavy smoking in middle age
seems to increase the risk for developing Alzheimer's disease or
another dementia, a large new study suggests.
"We found that people who reported heavy smoking in midlife had more than a 100 percent increase in risk of Alzheimer's disease and vascular dementia," said lead researcher Rachel A. Whitmer, a research scientist in Kaiser Permanente's Division of Research in Oakland, Calif.
"We have known that smoking is a risk factor for cancer, stroke and cardiovascular disease," she said. "This adds to the evidence that what is bad for the heart is bad for the brain."
The report is published in the Oct. 25 online edition of the
Archives of Internal Medicine.
For the study, Whitmer's group collected data on 21,123
ethnically diverse people in the Kaiser Permanente health care
system who were surveyed between 1978 and 1985, when they were 50
to 60 years old.
During an average follow-up of 23 years, the researchers found
that 25.4 percent were diagnosed with dementia, including
Alzheimer's (1,136 people) or vascular dementia (416 people), which
is the second most common form of dementia after Alzheimer's
disease. Vascular dementia is caused by damage to the arteries in
Compared with non-smokers, those who smoked more than two packs
of cigarettes a day in midlife had a "dramatic increase" in the
incidence of dementia -- more than a 157 percent increased risk of
developing Alzheimer's disease and a 172 percent increased risk of
developing vascular dementia, Whitmer's team found.
Former smokers and people who smoked less than half a pack a day
did not appear to be at increased risk of Alzheimer's or vascular
dementia, the researchers note.
The associations between smoking and dementia did not change
even after adjusting for race or gender, high blood pressure, high
cholesterol or heart attack, stroke or weight, they add.
A link between Alzheimer's and smoking has been shown before,
but this new study pinpoints the specific risk for middle-age
smokers for developing both Alzheimer's and vascular dementia, the
Smoking, an established risk factor for stroke, may contribute
to the likelihood of vascular dementia by causing small clots in
the brain. Smoking also contributes to oxidative stress and
inflammation, which may be linked to the risk of developing
Alzheimer's disease, the researchers say.
"The brain is not immune to long-term damage from smoking," Whitmer said.
Two smaller studies of predominantly white participants also
suggested that mid-life smoking raised the risk of developing
Alzheimer's, researchers noted.
Commenting on the new study, William Thies, chief medical and
scientific officer at the Alzheimer's Association, said "this is a
sound confirmation of something that's been known for a while."
Another expert, Dr. Samuel E. Gandy, the Mount Sinai Professor
of Alzheimer's Disease Research at Mount Sinai School of Medicine
in New York City, said the findings are promising.
"Environmental factors in Alzheimer's disease have been long sought, and, until now, only head injury has emerged," Gandy said. "Unlike head injury, a tobacco smoking association is especially important because that is a risk that can be modified."
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