Familial aggregation of olfactory impairment and odor identification in older adults

Objectives/Hypothesis: The objective of this analysis was to estimate the genetic contributions to olfactory impairment. Study Design: Population based. Methods: Olfactory impairment was measured using the San Diego Odor Identification Test at the 5-year follow-up examination for the population-based Epidemiology of Hearing Loss study. Subjects were classified as impaired if they correctly identified fewer than six out of eight odorants. To reduce confounding by age, analysis was restricted to subjects who were 60 to 79 years of age. Familial aggregation was evaluated by heritability estimates, tetrachoric correlations, and odds ratios in 207 sibling pairs from 135 sibships. Results: The prevalence of olfactory impairment was 20.2% overall and was higher in men. After adjustment for sex, age, and smoking, heritability of olfactory impairment was moderate (h² = 0.55), although not statistically significantly different from 0 (P = .09). By contrast, the adjusted heritability estimate for bubble gum, one of the individual odorants, was significant (h² = 0.51; P = .01). Conclusions: Genetic factors might contribute to general olfactory impairment in older adults, but the strength of familial aggregation differs for individual odorants, a finding consistent with prior research.