Researchers at the Hebrew University of Jerusalem in Israel examined the medical records of people with type 2 diabetes. They found that people taking GLP-1 were significantly more likely to be diagnosed with smell or taste disorders than those taking a different diabetes drug. Although the absolute risk appears to be small, researchers say more studies are needed to confirm whether GLP-1 may negatively affect some people’s sense of smell and taste.
“The findings highlight the need for closer surveillance and greater public health awareness,” they wrote in their paper published Thursday in JAMA Otolaryngology-Head and Neck Surgery.
Smelly?
GLP-1 drugs have greatly improved the treatment of type 2 diabetes and obesity. Yet no drug is completely risk-free. And as the popularity of GLP-1 has skyrocketed over the past few years, researchers have identified new, if generally rare, potential side effects associated with them.
Some reports have recently linked smell and taste issues to the use of GLP-1, which made the current study researchers curious to learn more. Researchers analyzed medical records from a large database of patients treated in more than 170 health care centers around the world. Finally, they compared the results of nearly 439,000 type 2 diabetes patients taking GLP-1 with a similar-sized group of patients, closely matched in age and other characteristics, who were taking another drug.
The researchers found that in both groups, the prevalence of newly reported smell or taste disturbances was low, but those taking GLP-1 were still 48% more likely to develop them. Overall, 0.37% of GLP-1 users were diagnosed with smell or taste problems in a matched comparison, compared with 0.22% of non-users. These included conditions such as anosmia (partial or complete loss of smell), parosmia (distorted sense of smell), and paragesia (distorted sense of taste).
what should it mean
This study is retrospective and observational, meaning it is not able to conclusively show a cause-and-effect link between GLP-1 and these sensory disturbances. The researchers also note that some studies have actually linked GLP-1 use to improved perception of taste and smell, although most of the people in these studies were taking GLP-1 for their obesity rather than type 2 diabetes. It is therefore possible that the risk of loss of smell and taste from these medications is complex and associated with multiple factors.
“Future research is needed to validate these findings and further explore the mechanisms underlying this association,” the authors wrote. For example, our taste buds and olfactory bulbs (the brain area that primarily controls smell perception) both contain GLP-1 receptors, so perhaps these drugs could directly affect the cells there.
Importantly, given the small absolute risk, the researchers are not telling everyone to dump their GLP-1s over their findings. But they still say doctors and patients should keep an eye on these symptoms. The sooner such issues are identified, the better the chance that treatments such as olfactory training can work to recover a person’s sense of smell and taste.
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