Associations between self-reported smell impairment and adiposity in adult women: Results from the 2011-2012 U.S. National Health and Nutrition Examination Survey (NHANES)

Background:  Smell impairments disproportionately affect older adults, decreasing detection of warning odors, and increasing risk of altered dietary behaviors and nutritional status. From just released data and new chemosensory protocol in NHANES 2011-2012, we examined, for the first time, associations between self-reported smell impairment and body mass index (BMI) in a nationally-representative sample of US adults.

Methods: NHANES 2011-2012 participants aged 40+ years (n=3603, mean age 60±12 years) reported by survey their smell ability, smell loss with age, and phantom odor symptoms. Smell impairment (yes/no) was defined from an index of three smell-related questions, previously shown to have good correspondence with measured olfaction. Participants varied in adiposity (34.2% overweight, 37.7% obese). Associations between constructed smell impairment index and BMI were examined via survey-weighted linear regression models controlling for age, race/ethnicity, education, physical activity, smoking, and income-to-poverty ratio. Models were stratified by sex and age (<65/≥65 years).

Results:The prevalence of self-reported smell impairment was 23%, which did not differ by sex, but showed age-related increases. In women <65 years, self-reported smell impairment was associated with a 1.4 unit increase in BMI (p<0.005), whereas in women ≥65 years, perceived impairment was associated with a 1.4 unit decrease in BMI (p<0.005). No significant associations were seen in men.

Conclusions: Smell impairment has broad implications for healthy aging—perceived impairments are prevalent in the US and may influence risk of obesity differently in younger versus older women. Future NHANES data can test whether diet mediates smell-adiposity associations and if measured and self-reported impairment interact to influence health outcomes.