Alcohol and Tobacco Consumption as Risk Factors for Alzheimer's Disease: A Collaborative Re-Analysis of Case-Control Studies

Abstract

A meta-analysis, involving the secondary analysis of original data from 11 case-control studies of Alzheimer's disease, is presented for alcohol consumption and cigarette smoking. Five studies included in the meta-analysis of alcohol consumption. Alcohol consumption was computed in terms of average weekly intake, measured in ounces of 'pure alcohol'. This variable was categorized into tertiles to represent low, medium and high intake. Analyses showed no excess estimated risk of Alzheimer's disease for any level of alcohol intake. Smoking was analysed in three different manners: (1) lifetime prevalence of smoking (ever/never)--this included eight studies; (2) amount smoked (less than or equal to one pack per day versus more than one pack per day)--this included seven studies; and (3) pack-years--including four studies. A statistically significant inverse association between smoking and Alzheimer's disease was observed at all levels of analysis, with a trend towards decreasing risk with increasing consumption (p(trend) = 0.0003). A propensity towards a stronger inverse relation was observed among patients with a positive family history of dementia, but the difference between this group and the group with no such history was not statistically significant. Although the observed disturbance in nicotinic receptor function in Alzheimer's disease may provide an explanation for these findings, possible biases related to the selection or survival of study subjects cannot be fully ruled out at this time. Prospective, community-based studies of incident cases of Alzheimer's disease are needed to document in detail the smoking history, age of onset of disease and survival of patients and cognitively intact people by smoking status.

Isolated and Joint Effects of Tobacco and Alcohol Consumption on Risk of Alzheimer's Disease

“…However, in a sample of patients with AD followed to autopsy, active smokers were significantly younger at onset of AD and also significantly younger at death than never smokers [29]. In our data mean age at disease onset was slightly lower in smoking than in non-smoking cases, a result also reported in other studies [1]. Our analysis of tobacco consumption considering available information on pre- viously suggested potential effect modifiers (duration and intensity of smoking, time since last smoking, age of onset of the disease, and ApoE4 allele) did not yield substantially different results.…”

“…served among smokers with dementia [28]. Besides, smoking could appear as a protective exposure if it delays onset of the disease [1]. However, in a sample of patients with AD followed to autopsy, active smokers were significantly younger at onset of AD and also significantly younger at death than never smokers [29].…”

“…After first reports found no association [1,9,10,15], more recent results point to a protective effect of alcohol, mostly associated to moderate intakes and to wine consumption [16][17][18]. But differences according to type of alcohol beverage consumed have not always been observed [19]; and increased risks have also been reported for heavy alcohol consumption [20].…”

“…Concerning tobacco, initial pooled analyses suggesting a protective effect [1,2] were later challenged by longitudinal and case-control studies finding increased risks [3][4][5][6][7], mostly in current or recent smokers. Interaction effects between smoking and the apolipoprotein E4 (ApoE4) allele have been suggested as well.…”

Can Clinical Data Predict Progression to Dementia in Amnestic Mild Cognitive Impairment?

“…In a number of population-based studies, it has been inversely associated with development of dementia, suggesting a possible protective effect. 87,88 Other studies have found the opposite. 30,60 A variety of explanations have been advanced to explain either possibility, ranging from selection of a 'hardy' subgroup of elderly smokers, to a protective role for central nicotinic receptors.…”