Smoking and risk of breast cancer in the Generations Study cohort

Table 1 Characteristics of 102,927 women from the Generations Study, recruited 2003–2013

Study population	No. of subjects	%
Year of birth
1908–1939	5917	5.8
1940–1949	21,488	20.9
1950–1959	24,735	24.0
1960–1969	23,749	23.1
1970–1996	27,038	26.3
Year of recruitment
2003–2005	33,807	32.9
2006–2007	48,489	47.1
2008–2013	20,631	20.0
Age at recruitment, years
16–34	23,289	22.6
35–44	23,116	22.5
45–54	24,385	23.7
55–64	23,837	23.2
65–74	7308	7.1
75–102	992	1.0
Age at menarche, years
7–11	20,658	20.1
12–14	62,291	60.5
15–19	9353	9.1
Not known or anomalous^a	10,625	10.3
Family history of breast cancer in first-degree relatives
No	87,030	84.6
Yes	15,897	15.4
Smoking status, at entry into cohort
Never smoked	66,013	64.1
Current smoker	8491	8.3
Former smoker	28,300	27.5
Ever smoker, status unknown at this time	123	0.1
Alcohol consumption, at entry into cohort
Never regular	10,574	10.3
Current drinker (< 60 g/day)	63,690	61.9
Current drinker (≥ 60 g/day)	1280	1.2
Current drinker, amount unknown	4306	4.2
Former drinker	13,513	13.1
Ever drinker, status unknown at this time	9564	9.3
Total number of subjects	102,927	100.0

Total number of subjects excludes 13 women (including 1 who developed breast cancer) with self-contradictory information for parity or smoking
^aIncludes 2 women reporting menarche before age 5 years, 23 at ages 20–33 years, and 23 reporting never having periods