%0 Journal Article %T Night-shift work and breast cancer – a systematic review and meta-analysis %A Ijaz, Sharea %A Verbeek, Jos %A Seidler, Andreas %A Lindbohm, Marja-Liisa %A Ojajärvi, Anneli %A Orsini, Nicola %A Costa, Giovanni %A Neuvonen, Kaisa %J Scandinavian Journal of Work, Environment & Health %D 2013 %8 September 39 %N 5 %@ 0355-3140 %F Ijaz2013 %X '

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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.

%K breast cancer %K cancer %K dose–response %K evidence synthesis %K meta-analysis %K night shift %K night-shift work %K shift work %K systematic review %R 10.5271/sjweh.3371 %U https://www.sjweh.fi/show_abstract.php?abstract_id=3371 %U https://doi.org/10.5271/sjweh.3371 %P 431-447