Table 3.

Rotating night shift work duration and incident colorectal cancer risk in the Nurses’ Health Study 2 (N = 113,371) 1989–2013

	No. of cases	Person‐yrs	RR (95%CI)1	p‐trend1 , 3	RR (95% CI)2	p‐trend2 , 3
NHS2 baseline rotating night shift work history in years
Never	183	970,255	1.0 (ref)		1.0 (ref)
1–2	102	741,924	0.74 (0.58, 0.95)		0.75 (0.59, 0.95)
3–4	83	503,839	0.90 (0.69, 1.17)		0.90 (0.70, 1.17)
5–9	42	218,082	1.02 (0.73, 1.43)		1.02 (0.72, 1.43)
10–14	21	88,147	1.15 (0.73, 1.81)		1.15 (0.73, 1.81)
15+	7	26,753	1.02 (0.47, 2.17)	0.44	0.97 (0.45, 2.09)	0.49
	438	2,549,000
NHS2 baseline rotating night shift work history in years4
Never	183	970,255	1.0 (ref)		1.0 (ref)
1–14	248	1,551,992	0.86 (0.71, 1.04)		0.86 (0.71, 1.04)
15+	7	26,753	1.01 (0.47, 2.17)		0.97 (0.45, 2.09)
	438	2,549,000
NHS2 updated rotating night shift work history in years
Never	149	780,176	1.0 (ref)		1.0 (ref)
1–4	187	1,262,145	0.77 (0.62, 0.96)		0.77 (0.62, 0.95)
5–9	60	329,260	0.92 (0.68, 1.24)		0.90 (0.66, 1.21)
10–14	27	120,745	1.03 (0.68, 1.55)		1.00 (0.66, 1.51)
15+	15	56,674	1.02 (0.60, 1.75)	0.69	0.96 (0.56, 1.64)	0.88
	438	2,549,000
NHS2 updated rotating night shift work history in years4
Never	149	780,176	1.0 (ref)		1.0 (ref)
1–14	274	1,712,149	0.82 (0.67, 1.00)		0.81 (0.66, 0.99)
15+	15	56,674	1.02 (0.60, 1.74)		0.96 (0.56, 1.64)
	438	2,549,000

¹ Adjusted for age (months) and follow‐up cycle.

² See footnote Table 2.

³ p‐trend was calculated using the midpoint of each category of rotating shift work duration in years (1–4, 5–9, 10–14, 15+).

⁴ Categories of shift work duration (Never, 1–14 years, 15+ years) were used to compare with our previously published results.