Table 3.

Breast cancer in Oxford after benign breast disease in year periods^a: time between admission for BBD and admission for breast cancer, number of women with breast cancer in the reference cohort, observed (Obs) number of women with cancer in the BBD cohort, expected (Exp) number of women with cancer in the BBD cohort, ratio of rate in BBD cohort to that in the reference cohort and 95% confidence intervals for the RR

Year periods	Time intervalsb	Obs	Exp	Adjusted RRc	95% confidence interval
1963–1978	All (2059)	422	211.4	2.2	2.0–2.4
1979–1988	All (1604)	296	151.5	2.1	1.9–2.4
1989–1999	All (779)	132	37.8	3.9	3.2–4.7
1963–1978	1st month	32	4.6	12.2	7.4–20.2
1979–1988	1st month	41	4.2	20.3	12.5–32.9
1989–1999	1st month	40	3.8	26.0	15.4–44.7
1963–1978	1–11 months	21	5.8	4.4	2.6–7.2
1979–1988	1–11 months	17	7.5	2.5	1.4–4.1
1989–1999	1–11 months	32	5.2	7.5	4.9–11.2
1963–1978	1–4 years	75	31.4	2.7	2.1–3.5
1979–1988	1–4 years	64	30.5	2.3	1.7–3.0
1989–1999	1–4 years	34	16.1	2.2	1.5–3.1
1963–1978	5–9 years	72	36.5	2.2	1.7–2.8
1979–1988	5–9 years	83	47.8	1.9	1.5–2.3
1989–1999	5–9 years	25	11.9	2.2	1.4–3.4
1963–1978	10–19 years	149	83.3	1.9	1.6–2.3
1979–1988	10–19 years	91	60.9	1.6	1.3–2.0
1963–1978	20+ years	73	49.9	1.5	1.2–2.0

^aThe number of women admitted with BBD from 1963 to 1978 was 8350, from 1979 to 1988 was 9988 and from 1989 to 1999 was 5134.

^bNumber of women with breast cancer in the reference cohort in parentheses.

^cAdjusted for age in 5-year age bands, time period in single calendar years and district of residence; comparing Obs/Exp in the BBD cohort (data in table) with Obs/Exp in the reference cohort (data not shown separately).