Lancet
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Previous studies suggested a protective effect of smoking on Alzheimer's disease, but most were case-control studies based on prevalent cases. The findings of prospective studies on the association between smoking and the risk of dementia are inconclusive. ⋯ Smoking was associated with a doubling of the risk of dementia and Alzheimer's disease. Our finding that carriers of the APOEepsilon4 had no increased risk of dementia suggests an interaction between smoking and the APOEepsilon4 genotype in the aetiology of Alzheimer's disease.