Abstract
Aim: To elucidate the effect of midlife smoking on the risk of dementia and Alzheimer's disease (AD), and the possible modification of this relation by the apolipoprotein E (APOE) epsilon 4. Methods: Participants of the Cardiovascular Risk Factors, Aging and Dementia study were randomly selected from population-based samples originally studied in midlife (1972, 1977, 1982 or 1988). After an average follow-up of 21 years, 1,449 persons (73%) aged 65-79 years took part in a reexamination in 1998. Results: Smoking in midlife increased the risk of dementia (odds ratio, OR: 4.93; 95% CI: 1.51-16.11) and AD (OR: 6.56; 95% CI: 1.80-23.94) among the APOE epsilon 4 carriers, but not among the APOE epsilon 4 noncarriers. Conclusion: Midlife smoking was associated with an increased risk of dementia and AD later in life only among those individuals carrying the APOE epsilon 4 allele. These results suggest that the association between smoking and AD may be complex and vary according to genotype. Copyright (C) 2010 S. Karger AG, Basel