Incidence and predictors of cognitive impairment and dementia in Aboriginal Australians: A follow-up study of 5 years.

Introduction: Aboriginal Australians are reported to develop dementia earlier than the general population. The causes remain unknown.

Methods: This was a longitudinal study of 363 participants aged ≥45 years. Consensus diagnoses were established for cognitive impairment or dementia.

Results: At follow-up, 189 people (mean ± standard deviation age, 65.4 ± 10.3 years) participated, as 109 (30%) had died and 65 (18%) were unavailable. The incidence of cognitive impairment or dementia was 52.6 (95% confidence interval 33.9, 81.5) per 1000 person-years (380.3 total person-years) and for dementia was 21.0 (10.5, 42.1) per 1000 person-years (380.3 person-years total) over the age 60 years. Longitudinal risk factors associated with a decline from normal cognition to impairment were age and head injury. Other associations with cognitive decline were stroke, head injury, nonaspirin analgesics, lower BMI, and higher systolic BP.

Discussion: Dementia incidence in Aboriginal Australians is among the highest in the world, and is associated with age and head injury.