The following is a summary of “Associations between olfactory dysfunction and cognition: a scoping review,” published in the January 2024 issue of Neurology by Jacobson et al.

Though potent in aging minds, olfactory dysfunction (OD) grip on younger cognition remains a fragrant enigma.

Researchers conducted a retrospective study to sniff out the link between non-COVID-related OD and cognitive changes in younger adults.

They conducted an extensive literature search on PubMed, Ovid Embase, Web of Science, and Cochrane Library for this scoping review. The primary outcome of interest focused on the correlation between olfactory dysfunction (OD) and cognitive functioning in adults under 60.

The results showed that 2,878 studies underwent title and abstract review, 167 experienced full-text reviews, and 54 were chosen for data extraction. Among these, 34 studies focused on individuals aged 18–60, while the remaining 20 included a more diverse population, mainly within the target age range but some above 60. Etiologies for smell loss included neuropsychiatric disorders (37%), idiopathic causes (25%), type 2 diabetes (7%), trauma (5%), infection (4%), intellectual disability (4%), and others (18%). Some studies reported multiple associations, occasionally mixed, resulting in more than 54 studies. In total, 21/54 studies showed a positive olfaction-cognition association, 7/54 showed no association, 25/54 reported mixed results, and only 1/54 showed a negative association.

Investigators concluded that though OD and cognition likely link up, the evidence weakens in younger adults, calling for more targeted studies free of confounding factors.

Source: link.springer.com/article/10.1007/s00415-023-12057-7