The Nightingale study: rationale, study design and baseline characteristics of a prospective cohort study on shift work and breast cancer risk among nurses

Table 3 Baseline socio-demographic characteristics of 59,947 participants

Characteristic	N (%)^a
Age at cohort entry
18–25 year	3,070 (5%)
26–35 year	8,351 (14%)
36–45 year	12,858 (21%)
46–55 year	22,139 (37%)
56–65 year	13,529 (23%)
Country of birth
Netherlands	57,701 (96%)
Born elsewhere	2,136 (4%)
Top-5 country of birth when born elsewhere: ^b
Former Dutch East Indies (Indonesia)	313 (15%)
Germany	269 (13%)
Suriname	266 (13%)
Belgium	196 (9%)
Antilles (Aruba, Bonaire, Curacao, St. Marten, St. Eustatius)	143 (7%)
Married or living together as married	48,258 (81%)
Highest educational qualification
Intermediate vocational education/community college)	31,593 (53%)
Higher vocational/professional education/college/university of applied science)	22,131 (37%)
University or higher	6,223 (10%)
Employment status (most applicable)
Employed/self-employed	51,401 (86%)
Home duties/caregiver/volunteer	3,348 (6%)
Unemployed (but able to work)	438 (<1%)
Retired	2,539 (4%)
Unable to work	1,663 (3%)
Studying	456 (<1%)
Monthly income estimate ^c
Low	799 (2%)
Medium	43,197 (81%)
High	9,117 (17%)

^aNumbers do not always add up to 100% due to missing values.
^bThe Dutch East Indies, Suriname and the Antilles were all Dutch colonies.
^cbased on linkage individual zip codes with income data of Statistics Netherlands; for each individual the allocated income is the average income in December 2008 in the individuals’ zipcode area (PC6); in December 2008 the cut off value for having a low income was based on 40% of people with lowest income) and that for a high income was based on 20% of people with highest income. Source: CBS Kerncijfers postcodegebieden 2008–2019, http://www.cbc.nl.

ISSN: 1471-2407