To What Extent Does Age at Death Account for Sex Differences in Rates of Mortality from Alzheimer Disease?

Abstract

Our objective was to compare sex-specific rates of death with Alzheimer disease (AD) or dementia as the underlying or associated cause of death using death records. Deidentified individual records on causes of death for all people aged 60 years or more who died in Australia during 2006-2014 (n = 1,104,684) were analyzed. There were 184,562 records with International Classification of Diseases, Tenth Revision, codes for dementia (AD, vascular dementia, or unspecified dementia). Death rate ratios for women versus men were estimated using Poisson regression. Women had a greater crude rate of death from all types of dementia than men (5.9 deaths per 1,000 person-years as compared with 3.8 deaths per 1,000 person-years), which disappeared after adjustment for age. For AD, the age-adjusted rate was higher among women (rate ratio = 1.14, 95% confidence interval: 1.12, 1.16), while for vascular dementia age-adjusted rates were higher for men (rate ratio = 0.80, 95% confidence interval: 0.78, 0.82). There was no evidence of a differential bias in coding of dementia type between men and women. Women's older age at death explained much of the sex-related difference in rates of death from AD or dementia. However, excess numbers of AD deaths among women and vascular dementia deaths among men remained, providing support for the hypothesis of greater biological risk of AD in women.