People with impairment in sense of taste and smell are likely to see improvement three years after a COVID-19 infection, suggested a study.

Loss of smell and taste was one of the early indicators of the infectious disease. However, subsequent variants have had far less impact on taste and smell, with the Omicron variant having almost no perceptible impact.

The study, published in JAMA Otolaryngology-Head & Neck Surgery, researchers investigated the long-term loss of the ability to smell and taste in 88 individuals who had mild symptoms of COVID who had tested positive for SARS-CoV-2 in March and April of 2020.

The prevalence of self-reported smell or taste dysfunction was 64.8 per cent, 31.8 per cent, 20.5 per cent and 15.9 per cent during the acute phase of COVID, at 1-year, 2-year, and 3-year follow-up, respectively, said the researchers from the University of Trieste, Italy.

If participants were age 50 or younger at the time of enrollment, they were less likely to report long-lasting loss of taste or smell.

The study led by suggests a favourable rehabilitation of smell and taste function over the 3-year observation period, with taste showing lower frequency and faster recovery than smell.

By year 3, there was no statistically significant excess of olfactory dysfunction (OD) between cases and controls (13.6 per cent vs 10.2 per cent).

"Patients with PCC (post-COVID condition) exhibiting chemosensory alterations should be reassured that a recovery of olfaction appears to continue over 3 years after initial infection," the researchers said.