Background: Although conflicting findings abound, gender-related differences in olfactory identification have received continuous attention. To our best knowledge, no systematic and quantitative research has examined gender differences in olfaction identification at various stages of life. The present study aimed to find out if there is gender difference in human olfaction identification in different life stages.
Methodology: Studies cited in the PubMed database were searched from its inception to August 2017 using the terms "olfact" or "smell" and "gender" or "sex". The effect size of each comparison was calculated. 24 studies were included in this meta-analysis.
Results: In this meta-analysis, we used Cohen's d to determine the effects sizes for the comparisons between women versus men among different groups. Its value was 0.18 (95% CI: -0.13 to 0.49) in Group A (age less than 18 years), 0.62 (95% CI: 0.43 to 0.81) in Group B (age 18-50 years), and 0.33 (95% CI: -0.01 to 0.66) in Group C. The effect was considered relatively small in Group A (age less than 18 years) and Group C (age more than 50 years), and a medium effect in Group B (age 18-50 years). Moreover, a significant difference was only present in Group B (age 18-50 years). Summarizing, the gender effect was only present in the group aged 18-50 years, in which women outperformed men significantly in odor identification.
Conclusions: This meta-analytic review indicated that the gender differences only exist in young adults (age 18-50 years), while absent in juveniles (age less than 18 years) or an aged cohort (age more than 50 years). Females outperformed males in the young adults.