In a study of people with mild cognitive impairment, a decreased sense of smell accurately predicted whose memory loss would progress to Alzheimer’s disease. The ability to diagnose Alzheimer’s before the onset of symptoms would allow physicians to treat it before extensive brain damage has occurred. The results were reported this month, at the 2014 Alzheimer’s Association International Conference in Copenhagen, Denmark.
A team led by Columbia’s Davangere Devanand, MD, professor of psychiatry (in neurology and in the Sergievsky Center), investigated a multi-ethnic (34 percent white, 30 percent African-American, 36 percent Hispanic) sample of 1,037 nondemented elderly people in New York City, with an average age of 80.7. The researchers assessed the participants in a variety of ways at three time periods: from 2004–2006, 2006–2008, and 2008–2010. The smell identification tests were administered, in English or Spanish, between 2004 and 2006.
In 767 subjects who were followed (after 270 of the original participants had died), lower odor-identification scores were significantly associated with the transition to dementia and Alzheimer’s disease, after controlling for such factors as demographic, cognitive, and functional measures and language of administration. For each point lower that a person scored on the smell test, the risk of Alzheimer’s increased by about 10 percent. Even in participants without baseline cognitive impairment, lower baseline smell-test scores—but not measures of verbal memory—were associated with cognitive decline.