Table 1. Main baseline characteristics of the subjects participating and not participating in the follow-up survey.

	Non participants	Participants	All subjects at baseline	p-value
	n = 140	n = 214	n = 354
Mean age (years), (sd)	33.2 (7.0)	34.2 (7.5)	33.8 (7.3)	0.242
Gender (%)				0.577
Male	49.3	46.3	47.5
Female	50.7	53.7	52.5
Smoking habits (%)				0.125
Non smoker	42.9	48.6	46.3
Ex-smoker	16.4	21.0	19.2
Current smoker	40.7	30.4	34.5
Age at onset of asthma (years), median	14.0	13.0	14.0	0.738
Age at onset of asthma (IQR * )	(5.0–25.0)	(6.0–22.0)	(6.0–24.0)
Asthma attacks in the last 12 months (%)	90.0	79.0	83.3	0.006
Current asthma drug use (%)	66.4	69.2	68.1	0.590
Asthma-like symptoms (wheezing, tightness, shortness of breath) in the last 12 months (%)	84.9	87.8	86.7	0.434
Chronic cough and phlegm (%)	33.1	33.3	33.2	0.963
Allergic rhinitis (%)	65.5	76.2	71.9	0.029
Lost work days in the last 12 months (%)	18.3	14.8	16.2	0.408
Impaired days in the last 12 months (%)	22.2	19.4	20.5	0.531
Hospital or emergency department admissions because of asthma, shortness of breath, or wheezing in the last 12 months (%)	10.4	5.6	7.4	0.099

^*IQR, Interquartile Range: (1^st quartile–3^rd quartile).

P-values refer to the comparison between non participants and participants.