International journal of epidemiology
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A meta-analysis, involving the secondary analysis of original data from 11 case-control studies of Alzheimer's disease, is presented for occupational exposures to solvents and lead. Three studies had data on occupational exposure to solvents. Among cases, 21.3% were reported to have been exposed; among controls, this figure was comparable (20.9%). ⋯ This resulted in a pooled matched relative risk of 0.71 (95% CI: 0.36-1.41). The meta-analysis was particularly useful in validating negative results from individual studies and in increasing the statistical power for the analysis of lead exposure, where stratum-specific cell sizes were frequently smaller than five in individual studies. However, since exposure in the various studies was ascertained in a rather broad manner, prospective studies are recommended which focus on high-risk occupational populations and which determine the incidence of Alzheimer's disease in these and comparable unexposed populations.
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Studies of risk factors for Alzheimer's disease have been hampered by low statistical power. The data from 11 case-control studies were pooled and re-analysed to evaluate the evidence for the association of Alzheimer's disease with family history of dementia and related disorders, parental age, medical history, and environmental factors. This paper gives a brief description of the participating studies and discusses the strategy that has been followed in the collaborative analysis.
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Data from case-control studies of Alzheimer's disease (AD) were pooled to examine the possible roles of history of depression, anti-depressant treatment and adverse life events as risk factors. History of depression was found to be associated with AD, although the effect was confined to late onset cases. ⋯ However, data were only available from two studies, limiting the power of the analysis. Also, no association was found with the three major life events considered in the pooled analysis: death of spouse, death of a child and divorce.
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In the EURODEM pooling and re-analysis of case-control studies of Alzheimer's disease it has been possible to examine putative risk factors with increased power to detect associations. The fundamental problems of case and control selection persist, such as use of prevalent cases, selection through contact with specific services, difficulties of control choice. Risk factors such as family history and head trauma are shown again, although the biases introduced in collection of exposure data could still account for these findings. ⋯ Improvement of cardiovascular indices may improve the cerebrovascular status of the population, possibly reducing the incidence of vascular dementia. Other broad strategies to maintain health and function would seem prudent, but specific recommendations to reduce the incidence of Alzheimer's disease, or to slow progression of the disorder cannot be recommended on the basis of these re-analyses. It is clear that more research is needed to understand the risks of different pathologies related to Alzheimer's disease as well as dementia and cognitive change generally in the population.(ABSTRACT TRUNCATED AT 250 WORDS)