Increased exhaled nitric oxide predicts new-onset rhinitis and persistent rhinitis in adolescents without allergic symptoms.

BACKGROUND

The fraction of nitric oxide in exhaled air (FE(NO)) is increased in rhinitis and asthma. We have previously suggested that elevated FE(NO) levels in the absence of asthma symptoms may be a sign of 'early asthma'. In the present study, we hypothesize that elevated exhaled NO levels may also precede rhinitis symptoms.

OBJECTIVE

To investigate in a cohort of adolescents whether or not increased exhaled NO levels at the age of 13-14 years predicted new-onset or persistent rhinitis within a 4-year period.

METHODS

A total of 959 randomly selected adolescents (13-14 years) completed a questionnaire on respiratory symptoms at baseline and follow-up, 4 years later. Exhaled NO was measured at baseline. After exclusion of subjects with asthma diagnosis or asthma symptoms at baseline, 657 participants were eligible for the present study.

RESULTS

Higher FE(NO) levels at baseline were associated with increased risk for new-onset (P = 0.009) and persistent rhinitis (P = 0.03) within a 4-year period. The risk of new-onset rhinitis was 2.32 (1.23, 4.37) [OR (95% CI)] times higher if FE(NO) > 90th percentile of the group without rhinitis at baseline. This increased risk for new-onset rhinitis was significant [2.49 (1.24, 5.01)] after excluding subjects with allergic symptoms. The risk of persistent rhinitis was 5.11 (1.34, 19.57) times higher if FE(NO) > 90th percentile of the group without rhinitis at baseline.

CONCLUSION

Elevated exhaled nitric oxide levels predicted incident and persistent rhinitis in this population-based study of adolescents. Moreover, these findings were consistent after excluding subjects with allergic symptoms. Thus, it appears that elevation of exhaled NO precedes airway symptoms and predicts development of rhinitis in subjects without allergic symptoms or family history of allergic disease.