An Explanation for Reports of Increased Prevalence of Olfactory Dysfunction with Omicron: Asymptomatic Infections.

The prevalence of olfactory dysfunction (OD) in people infected with the omicron variant is substantially reduced compared with previous variants. However, four recent studies reported a greatly increased prevalence of OD with omicron. We provide a likely explanation for these outlier studies and reveal a major methodological flaw. When the proportion of asymptomatic infections is large, then studies on the prevalence of OD will examine and report predominantly on non-representative cohorts, those with symptomatic subjects, thereby artificially inflating OD prevalence by up to ten-fold. Estimation of the true OD prevalence requires representative cohorts that include relevant fractions of asymptomatic cases.