Table 1.

Main characteristics of the parents and grandparents, according to the parental line

	Maternal line	Paternal line
N parents	n = 2233	n = 1964	P-valuea
Grandmother’s ever asthma, %	11.0	7.6	<0.001
Grandfather’s ever asthma, %	9.2	7.4	0.04
Grandparents’ education level, %			0.56
low	45.7	47.0
high	52.1	51.1
unknown	2.2	1.9
Grandmother’s smoking, %			<0.001
when the parent was in utero	10.5	6.7
during other periods (or unknown smoking period)	13.5	15.3
not smoking	76.0	78.0
Parent’s ages (years), median (range)	55 (40–67)	55 (40–67)	0.08
Parent’s ever asthma, %	18.3	12.7	<0.001
Parent’s education level, %			0.35
low	14.1	12.6
high	82.2	83.4
unknown	3.8	4.0
Father’s smoking initiation, %			–
<15 years of age	–	12.2
≥15 years of age	–	51.3
not smoking	–	36.6

^aObtained by using Pearson chi-square and Wilcoxon-Mann-Whitney tests.