The first study to look at the long-term effects of heavy smoking on dementia risk found that heavy smoking – two packs or more a day — in midlife more than doubles the risk of developing Alzheimer’s disease or vascular dementia.
“This study shows that the brain is not immune to the long-term consequences of heavy smoking,” said the study’s principal investigator, Rachel A. Whitmer, PhD, a research scientist with Kaiser Permanente Northern California’s Division of Research. “We know smoking compromises the vascular system by affecting blood pressure and elevating blood clotting factors, and we know vascular health plays a role in the risk of Alzheimer’s disease.”
Researchers analyzed data from more than 21,000 Kaiser Permanente Northern California members who participated in a survey between 1978 and 1985. Diagnoses of dementia, Alzheimer’s disease and vascular dementia were collected from 1994 to 2008.
“While we don’t know for sure, we think the mechanisms between smoking, and Alzheimer’s and vascular dementia are complex, including possible deleterious effects to brain blood vessels as well as brain cells,” said study co-author Minna Rusanen, MD, of the University of Eastern Finland and Kuopio University Hospital in Finland.
This study, published Oct. 25, 2010 online in the Archives of Internal Medicine, is the latest in a series published by Kaiser Permanente researchers, that help people better understand how to avoid dementia.
The gist of the mounting evidence is that what’s good for the heart is good for the brain. Midlife is not too soon to begin preventing dementia with good health.
Other studies led by Dr. Whitmer have found that:
- A large abdomen in midlife increases risk of late-life dementia
- Elevated cholesterol levels in midlife increase risk of Alzheimer’s disease and vascular dementia
- Episodes of below-normal levels of blood sugar in elderly patients with type 2 diabetes increase dementia risk.
Researchers followed an ethnically diverse group of more than 21,000 men and women from midlife onward for an average of 23 years each. Compared with non-smokers, during the average follow-up period of 23 years, those who had smoked more than two packs of cigarettes a day had a more than 157 percent increased risk of developing Alzheimer’s disease and a 172 percent increased risk of having vascular dementia.
Vascular dementia, the second-most common form of dementia after Alzheimer’s disease, is a group of dementia syndromes caused by conditions affecting the blood supply to the brain.