157% Dementia-Risk for Heavy Smokers

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Heavy smoking in midlife is associated with a 157 percent increased risk of developing Alzheimer's disease and a 172 percent increased risk of developing vascular dementia, according to a Kaiser Permanente study published in the Archives of Internal Medicine.

Electronic health records were used to study 21,000 men and women for 20 years, making this a remarkably compelling piece of research.

This is the first study to look at the long-term consequences of heavy smoking on dementia.

Researchers followed an ethnically diverse population of 21,123 men and women from midlife onward for an average of 23 years. Compared with non-smokers, those who had smoked more than two packs of cigarettes a day had more than a 157 percent increased in risk of Alzheimer's disease and 172 percent increased risk of vascular dementia during the mean follow-up period of 23 years. 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.

"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, Ph.D., a research scientist with the Kaiser Permanente Division of Research in Oakland, Calif."We know smoking compromises the vascular system by affecting blood pressure and elevates blood clotting factors, and we know vascular health plays a role in risk of Alzheimer's disease."

Researchers analyzed prospective data from of 21,123 Kaiser Permanente Northern California members who participated in a survey between 1978 and 1985. Diagnoses of dementia, Alzheimer's disease and vascular dementia made in internal medicine, neurology, and neuropsychology were collected from 1994 to 2008. The researchers adjusted for age, sex, education, race, marital status, hypertension, hyperlipidemia, body mass index, diabetes, heart disease, stroke, and alcohol use.

"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 is the latest in a series of published Kaiser Permanente research to better understand the modifiable risk factors for dementia. This ongoing body of research adds to evidence base that what is good for the heart is good for the brain, and that midlife is not too soon to begin preventing dementia with good health.

Other authors of the paper include: Minna Rusanen, MD, the University of Eastern Finland and Kuopio University Hospital, Miia Kivipelto, MD, PhD, of the University of Eastern Finland and Karolinska Aging Research Center, and Charles P. Quesenberry, Jr, PhD, Jufen Zhou, MS. of the Kaiser Permanente Division of Research in Oakland, Calif.

Published:
Week of October 31 - November 7, 2010
Edited By:
Peter Berger, Alzheimer's Weekly
Medical accuracy review by:
Dr. Boaz Ancselovic, MD, Geriatrician, Alzheimer's Weekly.
Permalink:
http://www.AlzWeek.com/node/871

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http://www.ncbi.nlm.nih.gov/pubmed/20975015

Rusanen M, Kivipelto M, Quesenberry CP Jr, Zhou J, Whitmer RA. Heavy Smoking in Midlife and Long-term Risk of Alzheimer Disease and Vascular Dementia. Arch Intern Med Oct 25 2010

BACKGROUND: Smoking is a risk factor for several life-threatening diseases, but its long-term association with dementia is controversial and somewhat understudied. Our objective was to investigate the long-term association of amount of smoking in middle age on the risk of dementia, Alzheimer disease (AD), and vascular dementia (VaD) several decades later in a large, diverse population.

METHODS: We analyzed prospective data from a multiethnic population-based cohort of 21 123 members of a health care system who participated in a survey between 1978 and 1985. Diagnoses of dementia, AD, and VaD made in internal medicine, neurology, and neuropsychology were collected from January 1, 1994, to July 31, 2008. Multivariate Cox proportional hazards models were used to investigate the association between midlife smoking and risk of dementia, AD, and VaD.

RESULTS: A total of 5367 people (25.4%) were diagnosed as having dementia (including 1136 cases of AD and 416 cases of VaD) during a mean follow-up period of 23 years. Results were adjusted for age, sex, education, race, marital status, hypertension, hyperlipidemia, body mass index, diabetes, heart disease, stroke, and alcohol use. Compared with nonsmokers, those smoking more than 2 packs a day had an elevated risk of dementia (adjusted hazard ratio [HR], 2.14; 95% CI, 1.65-2.78), AD (adjusted HR, 2.57; 95% CI, 1.63-4.03), and VaD (adjusted HR, 2.72; 95% CI, 1.20-6.18).

CONCLUSIONS: In this large cohort, heavy smoking in midlife was associated with a greater than 100% increase in risk of dementia, AD, and VaD more than 2 decades later. These results suggest that the brain is not immune to long-term consequences of heavy smoking.