Mortality rates among African Americans and Caucasians with mild cognitive impairment (MCI) and Alzheimer’s disease are comparable and higher than rates in persons without cognitive impairment, according to a study in the June issue of Archives of Neurology.
Robert S. Wilson, PhD, Senior Neuropsychologist at the Rush Alzheimer’s Disease Center in Chicago, and colleagues conducted a longitudinal, population-based observational study in four adjacent urban neighborhoods in the Chicago area. The researchers included 1,715 persons who were diagnosed as dementia-free in a previous data collection; 802 (46.8%) had no cognitive impairment, 597 (34.8%) had MCI, 296 (17.3%) had Alzheimer’s disease, and 20 (1.2%) had other dementia forms. All-cause mortality was the main outcome measure.
Risk of death increased by 50% among patients with MCI (hazard ratio [HR], 1.48) and was almost threefold greater among individuals with Alzheimer’s disease (HR, 2.84). “These effects were seen among African Americans and whites and did not differ by race,” Dr. Wilson and study authors stated. For subjects with MCI, risk of death increased with the severity of cognitive impairment—this effect also did not vary by race (HR, 2.54 for African Americans; HR, 2.44 for Caucasians).
“A similar effect was seen among participants with Alzheimer’s disease, but it was slightly stronger for African Americans [HR, 3.38] vs. whites [HR, 1.62],” Dr. Wilson and his team continued.
The researchers also assessed whether association of severity of cognitive impairment with mortality in each condition varied across domains of cognition. Lower levels of function in nearly all cognitive domains were linked with increased risk of death in the MCI and Alzheimer’s disease groups; this is consistent with the global severity effect. “By contrast, in the simultaneous models, only perceptual speed was related to increased mortality in both groups, and there were no other associations in the other cognitive domains, suggesting a much more selective effect,” Dr. Wilson and colleagues noted.
“Overall, these results do not suggest strong racial differences in survival for persons with MCI and Alzheimer’s disease,” Dr. Wilson and authors concluded.