To evaluate the relation between midlife alcohol consumption and mild cognitive impairment and dementia in old age, and the possible modification of this relation by apolipoprotein E. Prospective, population based study. Populations of Kuopio and Joensuu, eastern Finland. Of 1464 men and women aged 65-79 years randomly selected from population based samples studied in 1972 or 1977, 1018 (70%) were re-examined in 1998 (after an average follow up of 23 years). Mild cognitive impairment and dementia in old age. Participants who drank no alcohol at midlife and those who drank alcohol frequently were both twice as likely to have mild cognitive impairment in old age as those participants who drank alcohol infrequently. The risk of dementia related to alcohol drinking was modified by the presence of the apolipoprotein e4 allele. The carriers of apolipoprotein e4 had an increased risk of dementia with increasing alcohol consumption: compared with non-carriers who never drank, the odds ratio for carriers who never drank was 0.6, for infrequent drinkers it was 2.3, and for frequent drinkers was 3.6 (the overall interaction term "drinking frequency(*)apolipoprotein e4" was significant (P = 0.04), as were the interactions "infrequent drinking(*)apolipoprotein e4" (P = 0.02) and "frequent drinking(*)apolipoprotein e4" (P = 0.03)). Non-carriers of apolipoprotein e4 had similar odds ratios for dementia irrespective of alcohol consumption. Alcohol drinking in middle age showed a U shaped relation with risk of mild cognitive impairment in old age. Risk of dementia increased with increasing alcohol consumption only in those individuals carrying the apolipoprotein e4 allele.
