Exhaled nitric oxide: The effects of age, gender and body size

Since little is known of the effects of age, gender, and body size on exhaled nitric oxide (NO) production, we have conducted a prospective study to examine these factors in a healthy nonsmoking women (mean age +/- SD 47.7 +/- 15.8, range 20-79 years). Exhaled NO was measured by an automatic chemiluminescence analyzer (Sievers NO Analyser 280) at steady expiration. Men had significantly higher exhaled NO levels than women (p = 0.001). Although exhaled NO levels did not correlate with age (r = 0.12, p = 0.17), it correlated significantly with height (r = 0.23,p = 0.02), weight (r = 0.34,p < 0.001), body mass index (r = 0.25,p = 0.009), and body surface area (r = 0.42,p < 0.001) for the entire cohort. After making adjustment for age, height, weight, body mass index, and body surface area, exhaled NO levels were still significantly higher for men than for women (p = 0.004). Our data, therefore, could help explain the discrepancy in results of previous studies on exhaled NO production, which had not taken these parameters into account. Our findings should help researchers design future studies on evaluation of exhaled NO levels.