Correlates of olfactory impairment in middle-aged non-diabetic Caucasian subjects with stage I-II obesity.

Purpose: This study evaluates among middle-aged subjects with obesity the prevalence of olfactory impairment (OI) with respect to normative values and its correlation with body composition, cognition, sleep quality, and inflammation.
Methods: In 60 (31 women, 29 men) volunteers with a body mass index ≥ 30 to ≤ 40 kg/m ² , aged ≥ 50 to ≤ 70 years, we assessed olfaction by the Sniffin' Stick test. We measured anthropometrics, body composition and metabolic profiles and evaluated cognition by the MiniMental State Examination (MMSE) and sleep disturbances by the Insomnia Severity Index (ISI). Patients were classified into two groups according to a total olfactory score (odor Threshold, Discrimination, Identification, TDI) below or above the 25th percentile from age and gender-adjusted normative data.
Results: Overall, 25 subjects (42%) had OI (TDI < 25th percentile). The largest differences between subjects with and without OI were observed in discrimination and identification scores, with a large overlap in olfactory threshold. Subjects with an abnormal TDI showed significantly higher fat mass index, ISI scores and urinary neopterin and lower MMSE scores than those without OI. By multivariable logistic regression, MMSE, ISI score and urinary neopterin were significantly associated to OI.
Conclusions: Among middle-aged subjects with stage I and II obesity, OI is highly prevalent and is independently associated with poor self-reported sleep quality, lower cognition scores and higher levels of the inflammatory marker neopterin.