Poor sense of smell linked to depression in older adults: study

A poor sense of smell has been linked to an increased risk of depression in older adults.

According to the new study from researchers at the Johns Hopkins University School of Medicine Baltimore, while a poor sense of smell might not cause depression, it could be an indicator for issues affecting overall health and wellbeing.

Lead author Vidya Kamath is an associate professor of psychiatry and behavioral sciences.

“We’ve seen repeatedly that a poor sense of smell can be an early warning sign of neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease, as well as a mortality risk,” Kamath said in a news release. “This study underscores its association with depressive symptoms. Additionally, this study explores factors that might influence the relationship between olfaction and depression, including poor cognition and inflammation.”

The study used data collected over eight years from 2,125 seniors who lived in community environments in the U.S. Tests regularly tracked subjects’ mobility, depression and ability to detect certain odours. When sense of smell was measured starting in 1999, nearly half had a normal sense (48 per cent) while the rest reported decreased sense of smell (28 per cent), known as hyposmia, or profound loss of smell (24 per cent), known as anosmia.

During the eight-year study, a quarter of participants (25 per cent) developed significant symptoms of depression. Through analysis, poor sense of smell was associated with a six per cent heightened risk of moderate to high depressive symptoms. Those with a stronger sense tended to be younger.

Researchers believe sense of smell and depression may be linked through both behavioural and biological factors. Smells are processed by the brain’s olfactory bulb, which is associated with important brain structures that enable memory, decision-making and emotions.

“Losing your sense of smell influences many aspects of our health and behavior, such as sensing spoiled food or noxious gas, and eating enjoyment,” Kamath said. “Now we can see that it may also be an important vulnerability indicator of something in your health gone awry. Smell is an important way to engage with the world around us, and this study shows it may be a warning sign for late-life depression.”

Researchers now plan to examine changes to the olfactory bulb to determine if it becomes altered in those experiencing depression. The peer-reviewed study was published Monday in the Journal of Gerontology: Medical Sciences.