Measured olfactory dysfunction without past-year symptom reporting: Prevalence and nutritional correlates in U.S. adults

To characterize discordance between measured olfactory function and past-year symptom reporting and examine nutritional correlates of measured dysfunction without such reporting.

This cross-sectional analysis used NHANES 2013-2014 data from adults aged ≥ 40 years. Measured dysfunction was defined as ≤ 5 correct responses on an eight-item odor-identification test. Survey-weighted models compared participants with dysfunction versus normal scores, both without past-year symptom reporting. The primary outcome was day-1 Healthy Eating Index-2015 (HEI-2015). A National Cancer Institute model estimated usual protein intake; six secondary comparisons underwent false-discovery-rate correction. Post-review sensitivity analyses assessed cognition, sinonasal factors, impairment severity and measured anthropometry.

Among 3,515 participants, 531 had measured dysfunction without symptom reporting (weighted prevalence, 10.9%; 95% confidence interval [CI], 8.8%-13.0%). Among participants with dysfunction, 80.5% reported no past-year problem, equivalent to symptom-question sensitivity of 19.5% (95% CI, 14.9%-24.1%). In 2,599 complete cases, the adjusted HEI-2015 difference was - 0.09 points (95% CI, - 2.37 to 2.20; P=.937). No original secondary comparison met the false-discovery-rate threshold (minimum q=0.096). Additional analyses did not establish a consistent nutritional deficit.

Measured olfactory dysfunction frequently occurred without past-year symptom reporting, although nonreporting does not establish unawareness. This phenotype showed no clear difference in day-1 HEI-2015; protein findings remained exploratory. Its clinical relevance warrants prospective assessment with comprehensive olfactory and nutritional measures.