International journal of epidemiology
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In a re-analysis of eight case-control studies on Alzheimer's disease we explored several medical conditions that had previously been suggested as possible risk factors for Alzheimer's disease. History of hypothyroidism was increased in cases as compared to controls (relative risk 2.3; 95% confidence interval 1.0-5.4). ⋯ More cases than controls reported epilepsy before onset of Alzheimer's disease (relative risk 1.6; 95% confidence interval 0.7-3.5), especially for epilepsy with an onset within 10 years of onset of dementia. Neurotropic viruses, allergic conditions, general anaesthesia and blood transfusions were not associated with Alzheimer's disease.
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A re-analysis of the data from 11 case-control studies was performed to investigate the association between head trauma and Alzheimer's disease (AD). To increase comparability of studies, exposures were limited to head trauma with loss of consciousness (hereafter referred to as 'head trauma') and comparisons were restricted to community (versus hospital) controls. Test for heterogeneity across studies was negative; consequently, data were pooled in subsequent analyses. ⋯ There was no interaction effect between head trauma and family history of dementia, suggesting that these risk factors operate independently. Mean age of onset was not significantly different in cases with a history of head trauma compared to cases without such a history. The findings of the pooled analysis support an association between reported head trauma and AD.
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To investigate the possible association between Alzheimer's disease and late maternal age at index birth, we conducted a collaborative re-analysis of existing case-control data sets. Of the 11 studies participating in the EURODEM project, four were included in the analyses regarding maternal age. In all four studies, cases were matched to controls by age and gender, and only population controls were considered. ⋯ The association was confirmed by a test of consistency with the Down's syndrome risk model; results of this test were again more definite for sporadic Alzheimer's disease. In addition, three of the four studies also suggested an increased risk for maternal age at index birth between 15 and 19 years (overall relative risk = 1.5; 95% confidence intervals: 0.8-3.0). Although consistency across studies was not always complete, only some of the increased relative risks reached statistical significance, and information regarding maternal age obtained through a next-of-kin interview may have limitations, our study suggests that both early and late maternal age should be further investigated as possible risk factors for Alzheimer's disease.
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Meta Analysis
Familial aggregation of Alzheimer's disease and related disorders: a collaborative re-analysis of case-control studies.
Case-control studies of Alzheimer's disease were re-analysed to examine the association of Alzheimer's disease with family history in first degree relatives of dementia, Down's syndrome and Parkinson's disease. Overall, the relative risk of Alzheimer's disease for those with at least one first degree relative with dementia was 3.5 (95% confidence interval 2.6-4.6). Stratification according to age of onset of Alzheimer's disease showed that the relative risk decreased with increasing onset age. ⋯ The relative risk of Alzheimer's disease was significantly lower in patients who had one first degree relative with dementia (relative risk 2.6; 95% confidence interval 2.0-3.5) as compared to those who had two or more affected relatives (relative risk 7.5; 95% confidence interval 3.3-16.7). Furthermore, the re-analysis showed a significant association between Alzheimer's disease and family history of Down's syndrome (relative risk 2.7; 95% confidence interval 1.2-5.7), which was strongest in those patients who had a positive family history of dementia. The relative risk of Alzheimer's disease for those with a positive family history of Parkinson's disease was 2.4 (95% confidence interval 1.0-5.8).
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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 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'. ⋯ 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.