Table 1

Demographic and reproductive characteristics of Kaiser Permanente members with incident breast cancer diagnosed 1973–1995 and controls

Cases and controls were ≤12 years old at first entry into Kaiser Permanente during 1946–1975.

CharacteristicCases (%) n = 189Controls (%) n = 201
Age at reference date, yr
26–3543 (22.8)51 (25.4)
36–4056 (29.6)54 (26.9)
41–4555 (29.1)60 (29.9)
46–5935 (18.5)36 (17.9)
Year of reference date
1974–198748 (25.4)54 (26.9)
1988–199036 (19.0)37 (18.4)
1991–199348 (25.4)56 (27.9)
1994–199557 (30.2)54 (26.9)
Ethnicity
White141 (74.6)155 (77.1)
African-American32 (16.9)33 (16.4)
Other16 (8.5)13 (6.5)
Marital status
Single27 (14.3)33 (16.4)
Married113 (59.8)85 (42.3)
Other36 (19.0)18 (9.0)
Unknown13 (6.9)65 (32.3)
Alcohol use
Nondrinker43 (22.8)42 (20.9)
Drinker128 (67.7)119 (59.2)
Unknown18 (9.5)40 (19.9)
Parity
Nulliparous53 (28.0)62 (30.8)
142 (22.2)36 (17.9)
262 (32.8)48 (23.9)
≥332 (16.9)37 (18.4)
Unknown0 (0.0)18 (9.0)
Age at first full-term birth, yr
Nulliparous53 (28.0)62 (30.8)
15–1937 (19.6)25 (12.4)
20–2438 (20.1)51 (25.4)
25–2935 (18.5)20 (10.0)
30–4220 (10.6)17 (8.5)
Unknown6 (3.2)26 (12.9)
Age at menarche, yr
9–1138 (20.1)33 (16.4)
1248 (25.4)45 (22.2)
1342 (22.2)37 (18.4)
14–1822 (11.6)27 (13.4)
Unknown39 (20.6)59 (29.4)
Menopausal status
Premenopausal148 (78.3)132 (66.0)
Postmenopausal29 (15.3)18 (9.0)
Unknown12 (6.3)50 (25.0)
Mother’s history breast cancera
Yes38 (20.1)15 (7.5)
No150 (79.4)183 (91.0)
Unknown1 (0.5)3 (1.5)
Mother’s history of any cancera
Yes57 (30.2)34 (16.9)
No128 (67.7)162 (80.6)
Unknown4 (2.1)5 (2.5)
  • a Those for whom there was no mention of personal history of breast cancer in the mother’s record are coded “No.” Those for whom more than 10 years had elapsed since last chart entry before the diagnosis date or reference date are coded as “Unknown.”