ALZHEIMERS-DISEASE AFTER REMOTE HEAD-INJURY - AN INCIDENCE STUDY

Objective-To remote head injury as a risk factor for subsequent dement ia due to Alzheimer's disease. Methods-271 participants of a community based longitudinal study of aging in north Manhattan without evidence of significant cognitive impairment were interrogated for a history o f head injury on two occasions at entry into the study. The examining physician sought a history of head injury with loss of conciousness. I ndependently, a risk factor interviewer inquired about a history of he ad injury with loss of consiousness or amnesia, the duration of any lo ss of consiousness, and the date of the head injury. Patients were fol lowed up with standardised annual evaluations for up to five years to determine the first occurrence of dementia. Results-Over the course of the study incident dementia due to probable or possible Alzheimer's d isease was diagnosed in 39 patients. Cox proportional hazards modellin g showed that a history of head injury with loss of consiousness repor ted to the physician was associated with earlier onset of dementia due to Alzheimer's disease (relative risk (RR) = 4.1, 95% confidence inte rval (95% CI) 1.3-12.7). head injury with loss of consiousness or amne sia reported to the risk factor interviewer was not significantly asso ciated with earlier onset of Alzheimer's disease overall (RR 2.0, 95% CI 0.7-6.2), but those who reported loss of consiousness exceeding fiv e minutes were at significantly increased risk (RR 11.2, 95% CI 2.3-59 .8). Incident Alzheimer's disease was significantly associated with he ad injury which occurred within the preceding 30 years (RR 5.4, 95% CI 1.5-19.5). Conclusion-The results of this cohort study are consistent with the findings of several case-control studies suggesting that hea d injury may be a risk factor for Alzheimer's disease.