Chronic Cigarette Smoking Associates Directly and Indirectly with Self-Reported Olfactory Alterations: Analysis of the 2011-2014 National Health and Nutrition Examination Survey (NHANES).

Introduction: Population-based studies show inconsistent effects of cigarette smoking on olfactory function. We aimed to identify direct and indirect associations between measures of smoking exposure/nicotine dependence and altered olfaction in a nationally-representative sample of adults.

Methods: NHANES 2011-2014 (n=7,418) participants (mean age=57.8±12.2 years) self-reported olfaction and related health and demographic risks. Affirmative answers to three questions defined altered olfaction (olfactory problems in past year; worse ability since age 25; phantom smells). Smoking (never, former, current) was self-reported by chronicity (pack years, PY) and dependency (time to first cigarette upon waking), and verified by serum cotinine. Associations were tested with logistic regression, reporting odds ratios (OR) and 95% confidence intervals (CI), and mediation models.

Results: Estimated prevalence of altered olfaction was 22.3%, with age-related increases. Nearly half of the sample were former/current smokers (47.4%). Controlling for olfactory-related risks, ≥10 PY smokers had significantly greater odds of altered olfaction versus never smokers [OR 1.36, CI: 1.06-1.74]. The odds of altered olfaction were heightened among current smokers (≥10 PY) who also had high nicotine dependence (smoked ≤30 minutes of waking) [OR 1.41, CI: 1.01-1.99]. Light smokers (≤10 PY smokers) did not show increased odds versus never smokers. Current smokers who also were heavy drinkers (≥4 drinks/day) had the highest odds for altered olfaction (OR 1.96, CI: 1.20-3.19). Olfactory-related pathologies (sinonasal problems, serious head injury, tonsillectomy, xerostomia) partially-mediated the association between smoking and altered olfaction.

Conclusions: Chronic cigarette smoking was associated with increased odds of self-reported olfactory alterations, directly and indirectly via olfactory-related pathologies.

IMPLICATIONS: Analysis of U.S. nationally-representative data revealed significant positive associations between chronic smoking and alterations in the sense of smell. Rates of smell alteration (self-reported problems in the past year, losses with aging, phantom smells) increased from 23% among adults to 33% for chronic smokers and 38% for chronic smokers who also reported heavy drinking. Chronic smoking showed associations with smell alteration that were direct and indirect through exposure to olfactory-related pathologies (naso-sinus problems, dry mouth, head/facial injury). Smell alteration can impact smokers' quality of life by challenging the ability to sense warning odors, food flavor, and olfactory-stimulated emotions and memories.