Title: Effect of Gender and Age on Odor Identification in Humans: A Meta-analysis

Xiaochun Wang

Shanghai University of Sport, China


Chenping Zhang is now a master student in Shanghai University of Sport, majoring in Applied Psychology; Her research focuses on “How sports will facilitate human’s olfaction”; She is the first author of the publication “Initiation of the age-related decline of odor identification in humans - A meta-analysis”, which was published in the Journal “Ageing Research Reviews” whose 2017 impact factor was 8.973.


The aim of this study was to investigate the gender and age effect on human olfaction. Data Source and Study SelectionWe initiated 2 steps to complete this investigation. First, Studies cited in the PubMed database were searched from its inception to March 2017 using the terms “olfac*” or “smell” and “ag*”. The effect size of each comparison was calculated. Second, we used “olfact*” or “smell” and “gender” or “sex” to search studies cited in the PubMed database from its inception to August 2017, then calculated the effect size of each comparison. The first step was to determine the decade in which olfactory function begins to deteriorate in healthy humans, and the second step was to find out if there is gender difference in human olfaction in different life stages. In first meta-analysis, the effect sizes as determined using Cohen’s d for the comparisons between 30–39.9- and 40–49.9-year-olds was 0.06 (95% CI:−0.17 to 0.29), between40–49.9- and 50–59.9-year-oldswas 0.62 (95% CI: 0.20–1.04), considered a medium effect size, and between 35-55-year-olds and those >55 years old was 1.12 (95% CI: 1.06–1.45), considered a very large effect. For second meta-analysis, the effect sizes as determined using Cohen’s d for the comparisons between female versus male in Group A (age<18years) was 0.18 (95% CI: −0.13 to 0.49), in Group B (age18-50years) was 0.65 (95% CI: 0.46 to 0.84), in Group C (ag e>50years), was 0.37 (95% CI: 0.02 to 0.71), which considered a relatively small effect in Group A (age<18years) and Group C (ag e>50years), and a medium effect in Group B (age18-50years). 1) Olfactory function deterioration, as determined by an impaired ability to identify odors, starts in the fifth decade of life in healthy humans. the comparison between 40–49.9- and 50–59.9-year-olds suggested the deterioration of olfaction from 50-year-olds and the comparison between 35-55-year-olds and those >55 years old deepened this conclusion; 2) the gender differences only existed in young adult (age 18-50years), other than in prepubertal (age< 18years) or aged cohort (age >50years).