. Author manuscript; available in PMC: 2018 Sep 1.

Published in final edited form as: Am J Epidemiol. 2017 Sep 1;186(5):532–540. doi: 10.1093/aje/kwx140

Table 5.

Associations of duration of rotating night shift work and estrogen receptor (ER) and progesterone receptor (PR) status of invasive breast cancer tumors during 24 years of follow-up (NHS: 1988–2012; NHS II: 1989–2013)

	ER+PR+			ER+PR−			ER-PR−

	No. of cases	Age-adjusted HR (95%CI)	Multivariable- adjusted HR (95% CI)^b	No. of cases	Age-adjusted HR (95%CI)	Multivariable- adjusted HR (95% CI)^b	No. of cases	Age-adjusted HR (95%CI)	Multivariable- adjusted HR (95% CI)^b	MV P_{heterogeneity}
NHS rotating night shift work history
Never	1390	Ref	Ref	319	Ref	Ref	327	Ref	Ref
1–14 yrs	1879	1.05 (0.98–1.13)	1.03 (0.96–1.10)	414	1.00 (0.86–1.16)	0.98 (0.85–1.14)	398	0.95 (0.82–1.10)	0.94 (0.81–1.09)
15–29 yrs	199	1.05 (0.90–1.22)	1.11 (0.95–1.29)	34	0.76 (0.53–1.08)	0.82 (0.57–1.17)	45	1.01 (0.74–1.38)	1.06 (0.77–1.45)
30+ yrs	54	0.92 (0.70–1.21)	0.96 (0.73–1.27)	11	0.74 (0.40–1.35)	0.77 (0.42–1.40)	8	0.59 (0.29–1.20)	0.63 (0.31–1.27)
	3522	p_trend = 0.56	p_trend = 0.33	778	p_trend = 0.12	p_trend = 0.21	778	p_trend = 0.34	p_trend = 0.47	p_het= 0.17
NHS II 1989 baseline rotating night shift work history (early career)
Never	708	Ref	Ref	112	Ref	Ref	200	Ref	Ref
1–9 yrs	1166	1.11 (1.01–1.22)	1.11 (1.01–1.22)	201	1.21 (0.96–1.52)	1.20 (0.95–1.52)	268	0.90 (0.75–1.08)	0.92 (0.76–1.11)
10–19 yrs	87	0.90 (0.72–1.13)	0.97 (0.77–1.21)	16	1.03 (0.61–1.74)	1.13 (0.66–1.92)	23	0.88 (0.57–1.35)	0.95 (0.61–1.46)
20+ yrs	5	1.33 (0.55–3.22)	1.59 (0.65–3.86)	1	1.29 (0.18–9.35)	1.61 (0.22–11.91)	2	2.08 (0.51–8.47)	2.14 (0.52–8.86)
	1966	p_trend = 0.67	p_trend = 0.32	330	p_trend = 041	p_trend = 026	493	p_trend = 0.44	p_trend = 0.70	p_het= 0.49
NHS II cumulative rotating night shift work (updated)^a
Never	539	Ref	Ref	81	Ref	Ref	146	Ref	Ref
1–9 yrs	1152	1.04 (0.94–1.15)	1.05 (0.94–1.16)	204	1.24 (0.96–1.61)	1.25 (0.96–1.62)	269	0.90 (0.73–1.10)	0.92 (0.75–1.12)
10–19 yrs	105	0.81 (0.66–1.00)	0.85 (0.69–1.05)	20	1.09 (0.67–1.78)	1.20 (0.73–1.96)	42	1.22 (0.86–1.72)	1.29 (0.91–1.82)
20+ yrs	24	1.50 (1.00–2.27)	1.63 (1.08–2.46)	2	0.79 (0.19–3.24)	0.88 (0.21–3.60)	2	0.50 (0.12–2.02)	0.53 (0.13–2.14)
	1820	p_trend = 0. 53	p_trend = 090	307	p_trend = 060	p_trend = 0.37	459	p_trend = 0.74	p_trend = 0.54	p_het= 0.71

For NHS II, analyses using updated duration of shift work excluded participants during the cycles in which they were missing shift work exposure information, resulting in fewer cases and person-years, compared to analyses using history of shift work reported at baseline in 1989.

Multivariable-adjusted models. See Table 2 footnotes for list of covariates.