Head Injury and the Risk of Alzheimer's Disease: A Case Control Study

OBJECTIVES: The objective of this study is to examine the association between Alzheimer's disease and head injury in elderly patients referred to an EMI unit. METHOD: An unmatched case control study comparing 198 cases of Alzheimer's disease (NINCDS-ADRDA diagnostic criteria) to selected controls (164 other dementias and 176 non-dementing group) with respect to history of head trauma, with or without loss of consciousness, prior to the onset of dementia. SETTING: EMI unit in Warrington serving an elderly population of 28,000. The subjects included all patients referred to and seen by the first author during a 2-year study period 1991-1993. MAIN OUTCOME MEASURE: Relative risk (odds ratio) of Alzheimer's disease. RESULTS: For having history of head injury, the odds ratio was 1.52 (0.98-2.35), significant only in male patients (OR 2.1 p < 0.05). For dementias other than Alzheimer's disease the odds ratio of head injury was 2.36 and 2.46 for all dementias combined (p < 0.05). CONCLUSION: The study confirms a positive association between reported head injury and Alzheimer's disease as well as non-Alzheimer type dementia. Head trauma did not appear to be a specific risk for Alzheimer's disease as previously claimed. The association was modified by sex being only significant in male patients.