The effects of age on exhaled breath nitric oxide levels

A variety of factors influence exhaled breath nitric oxide (ENO) but few studies have examined ENO at the extremes of adult age. This investigation explores whether there is a difference in ENO between groups of older and younger individuals. A total of 48 normal subjects consisting of 23 younger (median age - 24 years) and 25 older (median age - 72 years) participants were studied. Carefully defined clinical and spirometric parameters, smoking history, and drug/medication documentation were determined to insure normalcy. Measurements of ENO were made using ATS/ERS recommended methodologies. The older group consistently showed higher ENO concentrations than-the younger subjects; median ENO values were 36.9 and 18.7 ppb, respectively (p < 0.001). The statistical significance held true when adjusting for multiple testing with the Holm method and accounting for outliers and medication usage. ENO levels are significantly higher in a normal older population. Comparing ENO between individuals at the extremes of age may depict differences more decidedly. Whether elevated ENO reflects underlying airway inflammation in older persons remains unanswered. It is possible that the difference in NO concentrations between older and younger groups represents only a marker of past oxidant exposures and holds no clinical significance. Additional investigations are necessary to elucidate the mechanisms and significances of elevated NO levels in the aged.