The scent of freshly baked bread; the smell of a recently-mown lawn on a summer’s breeze; the aroma of an open bottle of wine – people often take particular delight in smell. But as we get older our olfactory function starts to decline. Interestingly, previous research has shown that adults with dementia have more difficulty distinguishing smells, compared to adults without dementia. However, we do not know whether this olfactory dysfunction is predictive of subsequent dementia.
A longitudinal study of 2,906 US adults aged 57-85 measured their ability to identify five odours (rose, leather, orange, fish and peppermint) using a validated test, then looked at the incidence of dementia five years later. They found that adults who had difficulty identifying the smells at baseline were more than twice as likely to have developed dementia by the five year follow up (odds ratio = 2.13, 95% CI 1.32-3.43). This was after controlling for age, sex, race and ethnicity, education, comorbidities, and cognition at baseline. Further, more errors in identification was associated with greater probability of dementia diagnosis (p=0.04). Unfortunately, as the authors admit, they did not control for confounders already associated with olfactory function, such as smoking or depression.
It is hoped that using such an odour identification test will be an efficient and cost-effective addition to current examinations that assess an individual’s risk of dementia, thereby allowing early interventions and give individuals more time to plan for their future. It may also be a useful tool for early diagnosis of Parkinson’s disease, which is also associated with olfactory dysfunction.
— Peter Chilton, Research Fellow
- Adams DR, Kern DW, Wroblewski KE, McClintock MK, Dale W, Pinto JM. Olfactory Dysfunction Predicts Subsequent Dementia in Older U.S. Adults. J Am Geriatr Soc. 2017.