Table 1.

Sociodemographics of the respondents.

Variables	Research population N = 659	Reference group Dutch population N (x1000)	p-value
Age in years (SD)		Dutch parentsa
Mean age of mothers in research/reference population	34.7 (4.81)	34.2	0.341
Mean age of fathers in research/reference population	32.1 (4.22)	31.3	<0.001
Gender, n (%)		Dutch population age 20–50 yearsb	<0.001
Male	86 (13.1)	3 304 (50.3)
Female	571 (86.9)	3 266 (49.7)
Missing	2
Ethnicity, n (%)		Dutch population age 20–50 yearsc	<0.001
Dutch	569 (86.9)	4 675 (70.6)
Other	86 (13.1)	1 932 (29.4)
Missing	4
Civil registry, n (%)		Dutch parentsd	<0.001
Single	19 (2.9)	572 (21.6)
Living together/married	637 (97.1)	2 024 (78.4)
Missing	3
Highest education level, n(%)e		Dutch population age 25–45 yearse	<0.001
Low	24 (3.7)	585 (30.9)
Middle	143 (21.8)	1643 (38.1)
High	490 (74.6)	1908 (29.4)
Missing	2
Number of children, n (%)		Dutch parentsf	0.0149
1	324 (49.5)	71.9 (44.2)
2	219 (33.5)	62.5 (38.5)
≥3	111 (17.0)	28.1 (17.3)
Missing	5

Missing values were excluded from the percentages.

^aReference population Dutch Parents (18). One sample t-test.

^bReference population Dutch population age 20–50 years (19). χ² test.

^cReference population Dutch population age 20–50 years (19). χ² test.

^dReference population Dutch population households (20). χ² test.

Low: primary education, lower vocational education, lower, and middle general secondary education.

Middle: middle vocational education, higher secondary education, and pre-university education.

High: higher vocational education and university.

Reference population Dutch population age 25–45 years (21). χ² test.

^fReference population Dutch parents (20). χ² test for trend.