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 traumawith 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. The pooled relative risk for head trauma was 1.82 (95% confidence interval: 1.26-2.67). Stratifiedanalyses showed stronger associations in cases without a positive family history of dementia and in males (versusfemales). Adjustment of the pooled relative risk for family history of dementia, education and alcohol consumption didnot alter significantly the association between head trauma and AD. There was no interaction effect between headtrauma and family history of dementia, suggesting that these risk factors operate independently. Mean age of onsetwas not significantly different in cases with a history of head trauma compared to cases without such a history. Thefindings of the pooled analysis support an association between reported head trauma and AD.
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