title: Circadian variation in exhaled nitric oxide in nocturnal asthma.
abstract: Asthma is characterized by airway inflammation and shows a circadian variation with nocturnal exacerbations. Because exhaled nitric oxide (ENO) measurement appears to be a noninvasive marker of airway inflammation, we examined the hypothesis that ENO would increase at night. In five nocturnal and five non-nocturnal asthmatics, ENO was measured at 4 P.M., 10 P.M., and 4 A.M. before and after bronchodilator. Both pre- and post-bronchodilator ENO (mean pre- and post-bronchodilator +/- SEM, ppb) unexpectedly fell significantly in nocturnal asthma from 4 P.M. (77.2 +/- 8.2) compared to 10 P.M. (68.4 +/- 8.7, p < 0.003) and 4 A.M. (66.0 +/- 8.5, p < 0.001) with no significant difference between 10 P.M. and 4 A.M.. In contrast, there were no significant differences in mean ENO at 4 P.M., 10 P.M., and 4 A.M. in non-nocturnal asthma. (51.3 +/- 10.8, 57.7 +/- 13.4, 53.8 +/- 12.5 ppb, respectively). Following bronchodilator, ENO rose significantly by 10.5 +/- 1.8 ppb in the nocturnal asthma group alone. The circadian rhythm of ENO differed greatly between nocturnal and non-nocturnal asthma. The significant decrease in ENO in nocturnal asthma may reflect an important chronobiological defect in the endogenous production and/or increased disposition of nitric oxide, which in view of its bronchodilator action, could play a role in nocturnal exacerbations of asthma.
authors.affiliation: National Jewish Medical and Research Center, and The University of Colorado Health Sciences Center, Denver, Colorado, USA.
authors.forename: G
authors.initials: G
authors.lastname: Georges
authors.forename: B B
authors.initials: BB
authors.lastname: Bartelson
authors.forename: R J
authors.initials: RJ
authors.lastname: Martin
authors.forename: P E
authors.initials: PE
authors.lastname: Silkoff
mesh_terms: D000328:Adult; D001249:Asthma / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology*; D001944:Breath Tests; D001993:Bronchodilator Agents / Q000627:therapeutic use; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D013147:Spirometry
chemical_list: D001993:Bronchodilator Agents; D009569:Nitric Oxide