December 23, 2009
People with Alzheimer's disease tend to die earlier than their mentally intact, age-matched peers. So do those with mild cognitive impairment, or MCI, a form of memory loss that sometimes precedes Alzheimer's. Both whites and blacks seem to be equally affected, according to a new study out of Rush University Medical Center in Chicago.
"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 noted. But in the current report, Robert S. Wilson, Ph.D., and colleagues at Rush found that both groups were at equally increased risk of early death. The findings appeared in the June issue of Archives of Neurology, one of the journals from the American Medical Association.
The researchers studied 1,715 older adults, average age 80, living in four neighborhoods in Chicago. About half were African-American. All were given a thorough medical checkup that included a neurologic exam as well as tests of thinking and memory.
At the start of the study, about one in six, or 296, were given a diagnosis of Alzheimer's; another 20 had another form of dementia. About one in three, or 597, were diagnosed with mild cognitive impairment. Just under half, or 802, remained mentally alert.
Doctors continued to evaluate the study participants over the next 10 years. During that time, 634 individuals, or 37 percent, died. The overall death rate consisted of 25 percent of those without cognitive impairment; 40 percent of those with mild cognitive impairment; 59 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 wrote. "These effects were seen among African Americans and whites and did not differ by race."
Among individuals with mild cognitive impairment, the 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 concluded.
Robert S. Wilson; Neelum T. Aggarwal; Lisa L. Barnes; Julia L. Bienias; Carlos F. Mendes de Leon; Denis A. Evans: "Biracial Population Study of Mortality in Mild Cognitive Impairment and Alzheimer Disease." Archives of Neurology, Volume 66, Number 6, pages 767-772.