Midlife Smoking Doubled Later Dementia Risk

People who smoked two packs of cigarettes or more a day at midlife were more than twice as likely as nonsmokers to develop dementia and dementia subtypes such as Alzheimer’s disease, according to a recent report.

The association between midlife smoking and dementia 2-3 decades later remained robust after the data were adjusted to account for several confounding factors, including stroke. Therefore, smoking “seems to have some independent effect on vascular dementia, beyond acceleration of cerebrovascular disease,” said Dr. Minna Rusanen of the department of neurology at the University of Eastern Finland, Kuopio, and her associates.

Few studies have addressed the long-term cerebrovascular consequences of smoking in middle age, and those that have done so had small sample sizes of predominantly white subjects, the investigators noted (Arch. Intern. Med. 2010 [doi:10.1001/archinternmed 2010.393]).

Dr. Rusanen and her colleagues used data from a large, multiethnic cohort of more than 33,000 members of the Kaiser Permanente Medical Care Program of Northern California. The study cohort took part in the Multiphasic Health Checkup and were first assessed at enrollment between 1978 and 1985, when they were aged 50-60 years. For the analysis, the medical records of 21,123 people who were still living and in the health plan in 1994 were reviewed for dementia diagnoses.

A total of 5,367 people (25%) were diagnosed by neurologists, neuropsychologists, or internists as having dementia, including 1,136 cases of Alzheimer’s disease and 416 cases of vascular dementia.

After researchers adjusted for age, sex, and certain cardiovascular risk factors, they found that people who smoked two or more packs per day at midlife were more than twice as likely as nonsmokers to develop dementia (risk-adjusted hazard ratio, 2.14), Alzheimer’s disease (HR, 2.57), or vascular dementia (HR, 2.72) 20-30 years later.

The association between smoking and dementia risk was analyzed separately for people who had stroke because stroke is a robust predictor of dementia and is highly associated with smoking. Midlife smoking remained a robust independent predictor of dementia and dementia subtypes in that subanalysis, the investigators said. Compared with nonsmokers who had a stroke, those who had smoked two or more packs per day and had a stroke were 1.83 times more likely to develop dementia.

The link between midlife smoking and later dementia remained robust when the data were adjusted for patient race, ethnicity, and gender. “The deleterious effects of smoking on risk of dementia seem to be the same for both sexes and across different ethnic groups,” Dr. Rusanen and her associates said.

The study was supported by Kaiser Permanente Community Benefits and several national institutions in Finland. One investigator report ed ties to Elan Corp., Pfizer, Janssen, and Novartis.

Dr. Philip Marcus, FCCP, comments:
Lung cancer, COPD, laryngeal cancer, esophageal cancer, wrinkles, and now dementia. One more reason to stop smoking, and even better, to never start smoking. This study provides conclusive evidence of the link between cigarette smoking and dementia and should cause every smoker to think, “wake up and smell the coffee,” and finally kick the habit.