Ishizuka et al. Allergy, Asthma & Clinical Immunology 2011, 7:15 http://www.aacijournal.com/content/7/1/15 Page 4 of 8 Figure 2 A gender difference in FENO and the percentage of students whose FENO was ≥ 38.0 ppb. In the 584 students ranging in age from 18 to 24 years, FENO was significantly higher in men than in women (**, p < 0.01) (A). Overall, 32.7% of the 584 students, including 41.2% of male students and 25.2% of female students, had FENO ≥ 38.0 ppb. The percentage of men was significantly higher than that of women (p < 0.01) (B). 6 (1.0%) had a nocturnal attack of shortness of breath, and 24 (4.1%) had a nocturnal attack of cough within the last year. Overall, 10.2% (27 of 266) of men and 7.2% (23 of 318) of women had wheezing. On the other hand, sig- nificantly more women (6.0%, 19 of 318) had a nocturnal attack of cough than men (1.9%, 5 of 266; p < 0.05). 3. The prevalence of asthma symptoms based on the ECRHS questionnaire and FENO measurement FENO was over 38.0 ppb in 42 (25 men and 17 women) of the 77 students who had any asthmatic symptoms. Thus, the prevalence of asthma symptoms over 1 year in Gunma University students was 7.2% of 584 students, based on our definition of a predictive FENO and the information about symptoms obtained from the ECRHS questionnaire (Figure 4B). As a result of this analysis, the prevalence of asthma symptoms was greater in men (9.4%) than in women (5.3%). 4. Past history of asthma and current subjective symptoms A total of 103 students (58 men and 45 women; 17.6% of 584 students) answered that they had suffered from asthma, including 21.8% of 266 male students and 14.2% of 318 female students; the difference between men and women was significant (p < 0.05) (Figure 5A). Thirty six (35.0%) of 103 students who suffered from asthma still had asthmatic symptoms (Figure 5B). Overall, 19 (32.8%) of 58 male students and 17 (37.8%) of 45 female students with a past history of asthma still felt any asthmatic symptoms. Of the 103 students who had suffered from asthma, 16 were being treated at the time of the survey, of whom only 3 had been treated well and had no asth- matic symptoms within the last year. Only 36.1% of the 36 students with current asthmatic symptoms and a past history of asthma were being treated medically at the time of the survey, and the other 63.9% were not being treated. A total of 41 students (14 men and 27 women) who did not have a past history of asthma and did not recognize themselves as having asthma had asthmatic symptoms within the last year. They accounted for 7.0% of the 584 students. Even if the students did not have a past history of asthma, they were also considered to have asthma when they had any asthmatic symptoms within the last year and their FENO was ≥ 38.0 ppb. FENO was ≥ 38.0 ppb in 11 (26.8%; 7 men and 4 women) of 41 stu- dents. A significantly greater percentage of men (50.0%) than women (14.8%) had a FENO ≥ 38.0 ppb (p < 0.05) (Figure 5C). 5. Nasal allergies including hay fever Of the 584 students, 314 (53.8%) answered “Yes” to the question “Do you have any nasal allergies including hay fever?” FENO was significantly higher in students who had any nasal allergies including hay fever than in other students (41.4 ± 32.2 ppb vs. 31.3 ± 25.4 ppb, mean ± SD, p < 0.01). The percentage of students who had any nasal allergies did not differ between men (54.9%, 146 of 266) and women (52.8%, 168 of 318). Discussion The gold standard of asthma diagnosis is obstructive lung disease with airway reversibility, or airway reactivity