Cognitive impairment linked to reduced survival regardless of race

June 8, 2009

Alzheimer's disease and its precursor, mild cognitive impairment, appear to be associated with an increased risk of death among both white and African American older adults, according to a report in the June issue of Archives of Neurology, one of the JAMA/Archives journals.

Alzheimer's disease reduces life expectancy and has emerged as a leading cause of death in the United States, according to background information in the article. "Data from two national surveys suggest that life expectancy among patients with Alzheimer's disease may be greater for African Americans than for whites," the authors write. "However, not all surveys have reported this difference. Furthermore, in these surveys, the diagnosis of Alzheimer's disease is not based on a uniform clinical evaluation but derived from medical records, increasing the likelihood of substantial variation in the quality of diagnostic classifications."

Robert S. Wilson, Ph.D., and colleagues at Rush University Medical Center, Chicago, studied 1,715 older adults (average age 80.1, 52.5 percent African American) from four adjacent neighborhoods in Chicago. Each participant had a clinical evaluation that included medical history, a neurological examination and cognitive (thinking, learning and memory) function testing. Based on these evaluations, an experienced physician diagnosed 296 (17.3 percent) of the participants with Alzheimer's disease, 597 (34.8 percent) with mild cognitive impairment and 20 (1.2 percent) with other forms of dementia, while 802 (46.8 percent) had no cognitive impairment.

During up to 10 years of follow-up (average observation period, 4.7 years) 634 individuals died (37 percent), including 25.8 percent of those without cognitive impairment, 40.4 percent of those with mild cognitive impairment, 59.1 percent of those with Alzheimer's disease and 60 percent of those with other forms of dementia. "Compared with people without cognitive impairment, risk of death was increased by about 50 percent among those with mild cognitive impairment and was nearly three-fold greater among those with Alzheimer's disease," the authors write. "These effects were seen among African Americans and whites and did not differ by race."

Among individuals with mild cognitive impairment, risk of death increased as cognitive impairment became more severe, another association that did not differ by race. A similar association between disease severity and survival was seen among patients with Alzheimer's disease, although that effect was slightly stronger for African Americans than for whites.

"Overall, these results do not suggest strong racial differences in survival for persons with mild cognitive impairment and Alzheimer's disease," the authors conclude.

Source: JAMA and Archives Journals (news : web)