Table 3.

Meta-analysis of night work and breast cancer

Authors (years)	Overall OR or RR (95% CI)	Night work exposure category
Megdal et al. (2005) [34]	1.51 (1.36–1.68)	Ever
Jia et al. (2013) [35]	1.20 (1.08–1.33)	Ever
	1.15 (1.03–1.29)	≥ 15 years
Kamdar et al. (2013) [36]	1.21 (1.00–1.47)	Ever
	1.04 (0.92–1.18)	≥ 8 years
Wang et al. (2013) [37]	1.19 (1.05–1.35)	Ever
	1.03 (1.01–1.05)	Every 5 years of exposure increased
Ijaz et al. (2013) [38]	1.05 (1.01–1.10)	Every 5 years of exposure increased
Travis et al. (2016) [39]	0.99 (0.95–1.03)	Ever
	1.01 (0.93–1.10)	≥ 20 years
	1.00 (0.87–1.14)	≥ 30 years

OR Odds ratio, RR Relative risk