August/September 2013 (vol. 10/2)

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Research Plus

Nightshift and breast cancer

There is insufficient current evidence to support a causal link between nightwork and breast cancer, according to this systematic review and meta-analysis. Sixteen studies of women doing nightwork met inclusion criteria (12 case–control and four cohort studies) – research on airline crew were among those excluded from the review, on grounds of possible exposure to cosmic radiation and time zone changes. The meta-analysis (12 included studies) showed a small, but significant raised risk for working at night for every five years’ nightwork (relative risk 1.05; 95% confidence interval 1.01–1.10). Meta-analysis of the cohort studies alone showed no increased risk, while there was an elevated risk when only case–control studies were included (RR 1.09; CI 1.02–1.20). Although there is insufficient evidence to establish a definite link, the authors point out that a causal relationship cannot be ruled out. None of the studies had a low risk of bias for all the study characteristics, and better exposure data is required.

Scandinavian Journal of Work, Environment and Health 2013; online first: doi: 10.5271/sjweh.3371


Occupational Health at Work August/September 2013 (vol. 10/2) pp41