Changes in Brain, Nose Contribute to Impaired Sense of Smell in Old AgeOlfactory sensory neurons in those 60 years old and over respond in a way that makes it more difficult for the individual to distinguish specific smells.

Why does this matter? This difficulty puts them at greater risk for poor nutrition and coming into contact with dangerous chemicals.

“We found clear changes in olfactory sensory neuron responses to odors for those 60 and up,” said Professor Diego Restrepo, Ph.D., director of the Center for NeuroScience at the University of Colorado School of Medicine, who led the researchers.

“When we presented two different odors to the olfactory sensory neurons of younger people they responded to one or the other. The sensory neurons from the elderly responded to both. This would make it harder for the elderly to differentiate between them.”

Researchers evaluated  a total of 440 participants categorized into one of the following age groups: individuals younger than 45 and individuals 60 and older. Researchers tested the olfactory sensory neurons (OSNs) in both age groups for their responses to two distinct odors as well as subsets of those odors.

Restrepo wanted to know if age-related differences in the function of OSNs might contribute to an impairment of the sense of smell. With the help of Monell Chemical Senses Center in Philadelphia, researchers biopsied cells from both age groups.

“Whereas cells from younger donors were highly selective in the odorants to which they responded, cells from older donors were more likely to respond to multiple odor stimuli… suggesting a loss of specificity,” the study said.

The scientists had expected to find fewer OSNs in older subjects and believed the neurons would be less likely to respond to stimuli. Surprisingly, they found that the older participants had as as many neurons as the young but the older group could not differentiate between two odors; instead, they blended together.

The results suggest that changes in nose and the brain contribute to smell loss in old age, Restrepo said.

The study is published in the latest issue of Neurobiology of Aging.

Source: University of Colorado Denver