Association between Body Mass Index (BMI) and fraction of exhaled nitric oxide (FeNO) levels in the National Health and Nutrition Examination Survey (NHANES) 2007-2010.

PURPOSE: Obesity is characterised by chronic, low-grade systemic inflammation. Elevated FeNO levels reflect airway inflammation in various lung diseases including asthma.

METHODS

This is a cross-sectional analysis of data from NHANES 2007-2010. Participants younger than 20 years old with history of cough/cold symptoms in the past 7 days, smoking, exercise in the previous hour, consumption of nitric oxide rich meats/vegetables, or use of inhaled corticosteroids during the previous 2 days were excluded. BMI (in kg/m2) was divided in to 4 categories: underweight (UW) (0-18.5), Normal (N) (≥18.5 to <25), Overweight (OW) (≥25 and <30) and Obese (O) ≥30.

RESULTS

There were a total of 149,629,652 weighted participants: UW (22,235,218), N (45,021,536), OW (5,1670,522) and O (50,199,974); 50.36% were men and 49.63% were women. The mean age increased with BMI category [p<.0001]. Mean FeNO levels (in ppb) increased with increasing BMI category: UW (12.52±1.05) N (16.25±0.64), OW (16.62±0.34), and O (16.78±0.39) [p=0.0035]. FEV1/FVC (%) decreased with increasing BMI category: UW (80.68) compared to N (78.51), OW (77.67) and O (78.72) [p=0.0014]. There is a weak yet statistically significant correlation between FeNO levels and both age, BMI. Multivariate analysis predicting FeNO based on BMI category, adjusting for age, gender, race and airway obstruction found age less than 60 years, male gender, certain races and UW BMI category were associated with statistically significantly lower FeNO levels.

CONCLUSIONS

Older age and male gender are associated with increased FeNO levels. Controlling for age, gender, and race, obese individuals have a statistically significantly higher FENO than underweight individuals.