Heavy smoking in midlife boosts Alzheimer's disease risk
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Heavy smoking in middle age seems to double the risk for Alzheimer's disease and other forms of dementia two decades later, a study in the Feb 28, 2010 issue of Archives of Internal Medicine suggests.
The association between cigarette smoking and risk of Alzheimer's disease has been controversial with some studies suggesting that smoking may reduce risk of cognitive impairment, according to background information in the study report.
Minna Rusanen, M.D., of University of Eastern Finland and Kuopio University Hospital, Kuopio, Finland, and colleagues analyzed data from 21,123 men and women aged 50 to 60 years and found heavy smoking was linked with Alzheimer's disease risk.
During an average of 23 years of follow-up, the researchers identified a total of 5367 Cases of dementia including 1136 cases of Alzheimer's disease and 416 cases of vascular dementia.
They found those who smoked more than two packs of cigarettes a day in middle age were more likely to suffer dementia overall and also Alzheimer's disease and vascular dementia compared with nonsmokers.
However, those who smoked in the past or smoked less than half a pack a day did not seem to increase the risk.
Heavy smoking in middle age was correlated with a 157 percent increased risk of developing Alzheimer's disease and a 172 percent increased risk of vascular dementia,according to researchers from Kaiser Permanente.
"It is possible that cigarette smoking affects the development of dementia via vascular and neurodegenerative pathways," Rusanen et al. wrote.
They concluded "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."
Alzheimer's disease strikes heavy smokers earlier
Early this year Ranjan Duara, MD, of the Wien Center for Alzheimer’s Disease at Mount Sinai Medical Center in Miami Beach, FL presented a study at the American Academy of Neurology 60th Anniversary Annual Meeting in Chicago saying heavy smokers suffer Alzheimer's disease earlier.
Duara's study shows that heavy smoking and another risk factor together reduced the age of onset of Alzheimer's disease by six to seven years, which means heavy smoking can boost the risk of the disease by more than 50 percent.
The study involved 938 people aged 60 and older who were diagnosed with possible or probable Alzheimer's disease.
Heavy smokers developed Alzheimer's disease 2.3 years earlier than those who were not heavy smokers. Heavy smoking participants with APOE å4 developed the disease 3 years earlier.
The effect of cigarette smoking on dementia in people who carry certain genes is particularly significant
Another study published early 2010 in Dementia and Geriatric Cognitive Disorders suggests that smoking in middle age can boost risk of Alzheimer's disease and other dementia.
Dr. Rusanen and colleagues conducted the Cardiovascular Risk Factors, Aging and Dementia study and found those who smoked in midlife were 4.93 times as likely to develop dementia and 6.56 times as likely to develop Alzheimer's disease as those did not smoke cigarettes.
But the association was only found among those who carried the apolipoprotein E (APOE) & epsi;4 allele, but not among those who did not carry the allele.
The results suggest that the effect of cigarette smoking on the risk of Alzheimer's disease and dementia vary by genotype.
By David Liu
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