Fractional exhaled nitric oxide (FeNO) in students in Northern Thailand: associations with respiratory symptoms, diagnosed allergy and the home environment

Figures & data

Table 1. Descriptive data on demographics and doctor diagnosed allergies (N = 270).

	n	%
Gender
Boy	124	45.9
Girl	146	54.1
Family education
Primary or lower	30	12.1
Secondary education	88	35.6
University education	129	52.2
Doctor diagnosed allergies
Pollen allergy	6	2.2
Cat allergy	8	3.0
Dog allergy	7	2.6
Cockroach allergy	6	2.2
House dust mite allergy	17	6.3
Mold allergy	5	1.9
Any type of allergy	21	7.8
Medical symptoms
Wheeze in the last 12 months	31	11.5
Diagnosed asthma (cumulative incidence)	15	5.6
Asthma attack in the 12 months	10	4.0
Current asthma medication	10	3.7
Current asthma (asthma attack or medication)	13	5.3
Rhinoconjunctivitis in the last 12 months	90	33.7
Eye symptoms in the last 3 days	115	42.8
Rhinitis symptoms in the last 3 days	185	68.8
Dyspnea in the last 3 days	103	38.3

Table 2. Descriptive data on FeNO, stratified by gender, family education and allergy.

	GM	GSD	N
Total	14.54	2.01	270
Boys	16.20	2.05	124
Girls	13.26	1.95	146
Primary or lower	15.66	1.86	30
Secondary education	13.22	1.90	88
University education	14.77	2.09	129
Doctor diagnosed allergy	24.12	2.20	21
No doctor diagnosed allergy	13.94	1.96	249

Difference in FeNO between boys and girls (p = 0.02) and between those with and without diagnosed allergy (p = 0.001) by Student’s t-test.

GM = geometric mean; GSD = Geometric standard deviation; N = number of students in the group.

Table 3. Proportion of students with low, intermediate and high FeNO levels (N = 270).

FeNO	Gender		Allergy diagnosed by doctor		Total
	Boy n  = 124 (%)	Girl n  = 146 (%)	Yes n  = 21	No n  = 249
Cut points: 20–35 ppb
<20 ppb	81 (65.3)	109 (74.6)	10 (47.6)	180 (72.2)	190 (70.4)
20 ≤ FeNO < 35 ppb	22 (17.7)	22 (15.1)	5 (23.8)	39 (15.7)	44 (16.3)
>35 ppb	21 (16.9)	15 (10.3)	6 (28.6)	30 (12.1)	36 (13.3)
Chi-2 test p-value	0.19		0.04

Table 4. Descriptive data on home environment and outdoor air pollution for the students (N = 270).

Home environment factors	n (%)
Cat keeping	38 (14.1)
Dog keeping	67 (24.8)
Visible indoor mold	24 (8.9)
Window pane condensation in winter	39(14.6)
Water leakage index
No water leakage	185 (68.5)
Water leakage one time (last year or last 5 years)	54 (20.0)
Water leakage both times (last year and last 5 years)	31 (11.5)
Second hand smoke (SHS)	42 (15.6)
Type of cooking fuel
Only electricity	15 (5.7)
Gas cooking, but no biomass cooking	189 (71.3)
Any biomass cooking	61 (23.0)
Biomass burning index (other sources than cooking)
No biomass burning at home	120 (44.4)
Biomass burning inside home or outside the home	51 (18.9)
Biomass burning inside home and outside the home	99 (36.7)
Outdoor air pollution (nearest monitoring station)	Mean concentration (city range) (µg/m^3)
PM10 3 days lag time	46 (31-81)
PM10 7 days lag time	46 (28-79)
Ozone 3 days lag time	26 (23-31)
Ozone 7 days lag time	28 (23-39)

Table 5. Associations between FeNO and reported health (N = 270).

Reported health variable	antilog Beta (95% CI)	p-value
Any diagnosed allergy	1.74 (1.24-2.43)	0.001
Hose dust mite allergy	1.67 (1.16-2.41)	0.006
Cat allergy	2.67 (1.47-4.86)	0.001
Doctor diagnosed asthma	1.03 (0.70-1.51)	0.890
Wheezing in last 12 months	1.02 (0.77-1.35)	0.878
Current asthma in last 12 months	1.03 (0.68-1.55)	0.889
Rhinoconjunctivitis in last 12 months	1.18 (0.98-1.42)	0.082
Eye symptoms in last 3 days	1.22 (1.03-1.46)	0.025
Rhinitis symptoms in last 3 days	1.23 (1.02-1.48)	0.032
Dyspnea in last 3 days	1.17 (0.98-1.40)	0.089

Current asthma was defined as asthma attacks or asthma medication.

Analyzed by two level (student, school) linear mixed models, adjusting for gender and family education level (one health variable per model).

Figure 1. Associations between FeNO, home environment and outdoor PM₁₀ in a mutually adjusted model (N = 270). Analyzed by two level (student, school) linear mixed models, adjusting for gender and family education level (all exposure variable with p < 0.1 in Table 6 included in the model)

Table 6. Associations between FeNO, home environment and outdoor air pollution (N = 270).

Home environment factors	Antilog Beta (95% CI)	p-value
Cat keeping	1.09 (0.85-1.41)	0.498
Dog keeping	1.17 (0.95-1.44)	0.130
Mold indoor	0.78 (0.57-1.05)	0.096
Dampness on the windows in winter	0.98 (0.75-1.28)	0.868
Water leakage index
No water leakage	1.00
Water leakage 1 time (12 months/5 years)	1.16 (0.93-1.45)	0.178
Water leakage both times	1.16 (0.87-1.56)	0.316
Second hand smoke (SHS)	1.08 (0.85-1.38)	0.514
Type of cooking fuel
Only electricity	1.00
Gas cooking, but no biomass	0.71 (0.49-1.02)	0.064
Biomass	0.80 (0.54-1.19)	0.265
Biomass burning index
No biomass burning	1.00
Biomass burning inside or outside house area	0.92 (0.72-1.17)	0.488
Biomass burning outside or outside house area	0.95 (0.78-1.16)	0.611
Air pollution factors
PM10 3 days	0.94 (0.89-1.00)	0.038
PM10 7 days	0.95 (0.90-1.00)	0.045
Ozone 3 days	0.79 (0.51-1.23)	0.297
Ozone 7 days	0.86 (0.73-1.01)	0.063

Analyzed by two level (student, school) linear mixed models, adjusting for gender and family education level (one exposure variable per model).