Table 2.

HRs for shift work exposure groups applying multiple Cox analysis for prediction of breast cancer* after baseline among female night workers, and with 95% CIs

	Duration of exposure, years	Cases/no cases	Complete follow-up HR (95% CI)†	Follow-up to 60 years HR (95% CI)‡
No night work versus ever night work
No night work	0	354/9320	1	1
Working nights for: (unadjusted)	1–45	109/3120	0.93 (0.75 to 1.16)	0.86 (0.70 to 1.07)
No night work	0	354/9320	1	1
Working nights for: (adjusted)§	1–45	109/3120	0.94 (0.73 to 1.22)	0.96 (0.74 to 1.24)
No night work versus years of shift work
No night work	0	354/9320	1	1
Working nights for: (unadjusted)	1–5	57/1614	0.94 (0.71 to 1.24)	0.85 (0.65 to 1.13)
	6–10	16/623	0.69 (0.42 to 1.14)	0.63 (0.38 to 1.04)
	11–20	18/596	0.81 (0.50 to 1.30)	0.72 (0.45 to 1.16)
	21–45	18/287	1.62 (1.01 to 2.60)	1.92 (1.19 to 3.08)
No night work	0	354/9320	1	1
Working nights for: (adjusted)§	1–5	57/1614	0.92 (0.65 to 1.29)	0.93 (0.66 to 1.31)
	6–10	16/623	0.79 (0.45 to 1.37)	0.79 (0.45 to 1.38)
	11–20	18/596	0.77 (0.43 to 1.38)	0.80 (0.45 to 1.42)
	21–45	18/287	1.68 (0.98 to 2.88)	1.77 (1.03 to 3.04)

Reference: non-exposed. N=13 656, total number of cases=463.

*No cancer as reference.

†Follow-up until 31 December 2010.

‡Follow-up until the age of 60.

§Adjusted for: age+education level+tobacco consumption+body mass index+having children+coffee consumption+previous cancer+use of hormones including oral contraceptives. Bold typeface indicates significance at p<0.05.