Associations between fractional exhaled nitric oxide (FeNO), asthma, respiratory symptoms and self-reported allergies in female university students in Kobe, Japan

Fractional exhaled nitric oxide (FeNO) is a non-invasive biomarker of Th2-driven airway inflammation. There is little data on determinants of FeNO in population studies in Japan. Our aim was to study associations between FeNO in female university students in Japan and asthma, respiratory symptoms, and self-reported allergies. Female students (18-23y) (n=197) answered a medical questionnaire and FeNO was measured by NIOX MINO (96.5% participation rate). Associations were studied using multiple linear regression with 10log transformed FeNO data adjusting for age, height and BMI. Mean FeNO was 12.2 ppb (SD=2.7) and 22.8% had FeNO above 25 ppb. Totally 1.5% were smokers, 15.7% had doctors9 diagnosed asthma, 12.2% current wheeze and 2.5% asthma medication. Totally 57.4% had any allergy (atopy) and 46.7% had pollen allergy. Cumulative incidence of asthma (p<0.001), doctors9 diagnosed asthma (P<0.001), current asthma (p=0.04), current wheeze (P = 0.01), pollen allergy (P=0.02), dog allergy (p=0.002), mould allergy (P=0.02), house dust mite allergy (P=0.001) and atopy (P=0.02) were associated with higher FeNO levels. In conclusion, asthma diagnosis, current respiratory symptoms, especially wheeze, and self-reported allergies can be determinants of increased FeNO in Japanese female students.