TY - JOUR T1 - Night-shift work and breast cancer – a systematic review and meta-analysis JO - Scandinavian Journal of Work, Environment & Health PY - 2013/9VL - 39 IS - 5 SP - 431 EP - 447 AU - Ijaz, Sharea AU - Verbeek, Jos AU - Seidler, Andreas AU - Lindbohm, Marja-Liisa AU - Ojajärvi, Anneli AU - Orsini, Nicola AU - Costa, Giovanni AU - Neuvonen, Kaisa M3 - doi: 10.5271/sjweh.3371 UR - https://www.sjweh.fi/show_abstract.php?abstract_id=3371 KW - breast cancer KW - cancer KW - dose–response KW - evidence synthesis KW - meta-analysis KW - night shift KW - night-shift work KW - shift work KW - systematic review N2 - '

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OBJECTIVE ': 'The aim of this review was to synthesize the evidence on the potential relationship between nightshift work and breast cancer.

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METHODS ': 'We searched multiple databases for studies comparing women in shift work to those with no-shift work reporting incidence of breast cancer. We calculated incremental risk ratios (RR) per five years of night-shift work and per 300 night shift increases in exposure and combined these in a random effects dose–response meta-analysis. We assessed study quality in ten domains of bias. Results We identified 16 studies: 12 case–control and 4 cohort studies. There was a 9% risk increase per five years of night-shift work exposure in case–control studies [RR 1.09, 95% confidence interval (95% CI) 1.02–1.20; I2=37%, 9 studies], but not in cohort studies (RR 1.01, 95% CI 0.97–1.05; I2 =53%, 3 studies). Heterogeneity was significant overall (I2=55%, 12 studies). Results for 300 night shifts were similar (RR 1.04, 95% CI 1.00–1.10; I2=58%, 8 studies). Sensitivity analysis using exposure transformations such as cubic splines, a fixed-effect model, or including only better quality studies did not change the results. None of the 16 studies had a low risk of bias, and 6 studies had a moderate risk.

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CONCLUSIONS ': 'Based on the low quality of exposure data and the difference in effect by study design, our findings indicate insufficient evidence for a link between night-shift work and breast cancer. Objective prospective exposure measurement is needed in future studies.

SN - 0355-3140 ER -