Sex Steroid Hormones and Olfactory Dysfunction in US Adults

Background Olfactory dysfunction is a common disorder linked to adverse health outcomes and is more prevalent in men than in women. Sex steroid hormones have been proposed to underlie these sex differences, but population-based evidence remains limited. Objective To examine the associations of serum free testosterone and estradiol with olfactory dysfunction in US adults and to explore sex and age differences. Methods We analyzed data from 2750 participants (1373 men and 1377 women) aged ≥40 years in the 2013-2014 National Health and Nutrition Examination Survey. Olfactory function was assessed using the 8-item Pocket Smell Test. Dysfunction was defined as a score ≤5. Serum sex hormones were measured by mass spectrometry, and free testosterone was calculated from total testosterone, sex hormone-binding globulin, and albumin. Survey-weighted multivariable logistic and linear regression models evaluated associations between hormone quartiles and olfactory dysfunction or test scores, adjusting for sociodemographic factors, lifestyle, comorbidities, and olfaction-related medical history. Results The weighted prevalence of olfactory dysfunction was 16.49% in men and 10.58% in women. Among men, higher free testosterone was associated with lower odds of olfactory dysfunction (adjusted odds ratio for highest vs lowest quartile, 0.47; 95% CI, 0.26-0.83; P for trend = .004), particularly in those older than 50 years. No significant associations were observed for free testosterone or estradiol in women. Conclusion Higher free testosterone levels are associated with a lower prevalence of olfactory dysfunction in men, whereas no clear hormone–olfaction associations were detected in women. Circulating testosterone may contribute to sex differences in olfactory performance.