Olfactory Dysfunction and Mental Health Disparities Within a US Population

Research continues to uncover the complex relationships between olfactory dysfunction (OD), a condition characterized by either a partial or complete loss of the sense of smell, and various comorbidities and health disparities. Among the disparities seen in OD, associations with mental health are increasingly recognized and include increased rates of psychological distress [1, 2]. Addressing mental health among patients affected by OD is critical for guiding effective individual and public health strategies [3]. This study characterizes mental health disparities among patients with OD in a large, contemporary cohort representative of the United States. Understanding mental health challenges in this population can serve to better direct individual and public health approaches to improve disease screening and management of patient populations with OD. An exploratory, cross-sectional analysis was performed using 2021 National Health Interview Survey (NHIS) data, which collects self-reported health status among a nationally representative sample of US households [4]. Adults (≥18 years of age) who answered: “During the past 12 months, have you had difficulty with your sense of smell or ability to detect odors?” were included. Subjects with answers including either “a little difficulty,” “moderate difficulty,” “a lot of difficulty,” or “cannot smell at all” were considered to have OD (primary outcome), while those with the response of “no difficulty” were considered not to have OD. Measures of mental health, as the primary independent exposures, included self-reported anxiety, depression, and life satisfaction. Anxiety and depression were encoded from multiple survey items, suggesting increased symptom burden and higher likelihood of diagnostic accuracy, as previously described [5]. Each was considered positive if patients reported experiencing these conditions “daily” and “weekly” in frequency, and the level of these symptoms was reported to be “a lot” or “somewhere between a little or a lot” but not “a little.” Additional self-reported mental health measures, including use of medications and social/healthcare support, were identified. Data were analyzed using R-studio (version 4.4.0), the “survey” (version 4.4.2) package, and 2021 NHIS sampling weights were used to produce representative national estimates. Significant covariate associations, identified by a univariate p-value ≤ 0.05, were included in final logistic regression models for each independent mental health variable of interest. Odds ratios (OR) and 95% confidence intervals (CIs) were reported, and p-values < 0.050 were considered statistically significant. Sample weighting provided a raw sample size of ∼28,600 US adults and generated a nationally representative sample of ∼240 million patients, with ∼26 million adults in the US reporting some severity of OD (raw N = 2944, ∼10.8%). Demographics and clinical differences between OD and non-OD patients are shown in Table 1. Patients with OD reported increased prevalence of anxiety and depression (24% vs. 18%, p < 0.01; 32% vs. 25%, p < 0.01), treatment with prescription medications (17% vs. 12%, p < 0.01; 13% vs. 10%, p < 0.01, respectively), and rates of social support needs being unmet (20% vs. 18%, p = 0.02). Despite similar rates of mental health therapy during the last year as non-OD patients, OD patients had higher rates of delaying (6.4% vs. 4.1%, p < 0.01) or refusing (7.1% vs. 3.9%, p < 0.01) therapy treatments due to costs. They also reported a higher prevalence of life dissatisfaction (6.9% vs. 4.5%, p < 0.01). Sub-group analyses separated by OD severity showed increased anxiety and depression in all groups compared to non-OD populations (18%, 25%, respectively): OD groups (little OD: 24%, 33%; moderate OD: 20%, 30%; severe OD/anosmic: 24%, 32%; p < 0.01). After multivariate adjustments for demographic and clinical variables, OD remained significantly associated with anxiety (OR = 1.19, 95% CI: 1.05–1.36, p < 0.01; Table 2), depression (OR = 1.26, 95% CI: 1.13–1.42, p < 0.01), and life dissatisfaction (OR = 1.54, 95% CI: 1.26–1.90, p < 0.01). Exploratory analyses failed to identify multicollinearity between anxiety, depression, and life satisfaction within final regression models (variance inflation factors < 2.0). When further adjusting for OD severity, little OD was associated with anxiety (OR = 1.26, 95% CI: 1.05–1.56, p = 0.01), depression (OR = 1.33, 95% CI: 1.13–1.56, p < 0.01), and life dissatisfaction (OR = 1.57, 95% CI: 1.20–2.04, p < 0.01), moderate OD was associated with life dissatisfaction (OR = 1.82, 95% CI: 1.20–2.77, p < 0.01), and severe OD was associated with anxiety (OR = 1.22, 95% CI: 1.02–1.46, p = 0.03) and depression (OR = 1.23, 95% CI: 1.04–1.47, p = 0.02). This study identified associations between patient-reported OD and measures of mental health including anxiety, depression, and life dissatisfaction. These findings provide potential insights into the mental health disparities faced by individuals with OD and suggest the need to facilitate screening and treatment interventions to address these complex issues in this population. OD appeared associated with increased odds of anxiety, depression, and life dissatisfaction, even after adjusting for socioeconomic status and comorbidities. This suggests that the psychological consequences of OD may not only reflect broader health inequities, but may also be linked to olfactory impairment itself. Emerging evidence from other sensory disorders underscores the importance of addressing mental health conditions in affected patients using interventions such as cognitive-behavioral therapy (CBT) [6-8]. However, there appears to be a critical research gap in evaluating improvement in mental health among patients with OD, even in those undergoing treatment for OD [9]. We suggest screening for mental health conditions in this population using validated questionnaires for anxiety and depression, which may facilitate referral to mental-health resources and consideration for tailored therapy interventions [10]. This study is limited by cross-sectional design and self-reported nature of OD and mental health features. The inability to characterize OD etiology limits the evaluation of mental health outcomes associated with causes of OD, suggesting an important inclusion for future evaluation. Future work should incorporate objective olfactory measures and validated psychiatric tools in prospective cohorts. The authors declare no conflicts of interest.