LOS ANGELES — Heavy smoking at middle age more than doubles the risk of Alzheimer’s disease and other types of dementia later in life, according to one of the first long-term studies to examine the issue.
Smoking has a clear effect on the heart and lungs, but whether it also damages the brain has been controversial. The study, published Monday in the Archives of Internal Medicine, overcomes some of the obstacles that have made it difficult to assess such a link. For example, some previous research suggesting that smoking doesn’t cause dementia mostly examined elderly people only for a short period of time.
Researchers in Finland, Sweden and the health plan Kaiser Permanente’s Division of Research surveyed 21,123 middle-aged Kaiser members between 1978 and 1985 and then followed them for an average of 23 years.
After controlling for other factors that can contribute to dementia, the study found a significant link with heavy smoking at middle age.
Compared with non-smokers, people who smoked two packs a day or more had a 114 percent increased risk of dementia (more than double), while people who smoked one to two packs a day had a 44 percent increased risk.
Middle-aged people who described themselves as former smokers did not appear to have an increased risk of later dementia.
