Older adults having difficulty in identifying common odours may be at a higher risk of cognitive impairment-a decline in thinking, learning, and memory abilities-which is a precursor to Alzheimer's disease, suggests a study.
Dr. Robert S. Wilson and his colleagues at Rush University Medical Center, Chicago, studied 589 older adults, who did not have cognitive impairment in 1997. The participants, having an average age of 79.9 years, were exposed to 12 familiar odours.
The participants were asked to match each odour to one of four possible alternatives, and were scored from one to 12 based on the number of correct responses.
The researchers say that 177 individuals developed mild cognitive impairment during the study, and the risk of developing mild cognitive impairment increased as odour identification decreased. According to them, participants who had scored below average on the odour identification test were 50 per cent more likely to develop the condition than those who scored above average.
Dr. Wilson says that the association between cognitive impairment and reduction in odour identification did not change even when it was considered that factors like stroke and smoking habits might have influenced the results.
The researcher also said that the impaired odour identification was also associated with lower cognitive scores at the beginning of the study, and with a more rapid decline in the memory of past experiences, memory of words and symbols, and perceptual speed.
"Among older persons without manifest cognitive impairment, difficulty in identifying odours predicts subsequent development of mild cognitive impairment," the authors conclude.
"The findings suggest that olfactory dysfunction can be an early manifestation of Alzheimer's disease ... and that olfactory assessment may be useful for early disease identification," they write.