Most adults who lose smell or taste due to COVID-19 infection regain those senses within months, but a quick recovery is more likely in those under 40, a new study finds.

It included 798 participants in an ongoing survey who reported a loss of either sense after testing positive for COVID.

"We did see about an 80% recovery rate in a six-month period or longer. However, 20% is still a lot of people, given the millions that have been afflicted with COVID-19," said study co-author Dr. Evan Reiter, vice chairman of otolaryngology-head and neck surgery at Virginia Commonwealth University School of Medicine in Richmond.

Along with age, pre-existing conditions also affected recovery of lost taste or smell. Those with a history of head injury and those who had shortness of breath while sick with COVID were less likely to recover their sense of smell. Those with nasal congestion had a better chance of doing so.

"Certainly a subset of those people who are congested might have just lost their sense of smell because they were badly congested, rather than because of nerve damage due to the virus, as in other cases," Reiter said.

The study was published recently in the American Journal of Otolaryngology.

Worldwide, there have been more than 230 million cases of COVID-19, according to the World Health Organization. If survey responses reflect worldwide trends, more than 20 million people could have lingering loss of smell or taste more than six months after their COVID diagnosis.

To date, nearly 3,000 people across the United States have taken part in the survey that tracks symptoms over time.

For people who've suffered smell loss due to COVID-19, smell training using essential oils may help, according to Reiter.

"I continue to recommend that to my patients," he said. "It's low-cost and low-risk."

Reiter explained that "it may get people a little bit more tuned into whatever level of function they have left so it might make them more sensitive and better able to use the remaining sensors and neurons that are working."

In previous survey findings, 43% of respondents reported feeling depressed and 56% reported decreased enjoyment of life in general due to loss of smell or taste.

The most common quality-of-life concern was reduced enjoyment of food (87%), and the inability to smell smoke was the most common safety risk (45%).