Associations of shift work and night work with risk of all-cause, cardiovascular and cancer mortality: a meta-analysis of cohort studies.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational cohort studies
PubMed 34479052 · doi:10.1016/j.sleep.2021.08.017
What was done
Embase, PubMed, Web of Science, and Scopus were searched through March 2021 for cohort studies examining associations between shift work or night work and all-cause, cardiovascular, or cancer mortality. Study quality was evaluated using the Newcastle-Ottawa Scale. Study-specific risk estimates were pooled using fixed-effect or random-effects models depending on heterogeneity. Seventeen articles representing 16 cohorts and 958,674 participants (38,413 total deaths, 24,713 cardiovascular deaths, 10,219 cancer deaths) were included.
What was found
Fifteen studies were rated as high quality with low risk of bias, and no publication bias was detected. Compared with regular daytime workers, ever exposure to shift work yielded pooled relative risks of 1.02 (95% CI: 0.99, 1.06) for all-cause mortality, 1.18 (95% CI: 0.94, 1.47) for cardiovascular mortality, and 1.05 (95% CI: 0.83, 1.34) for cancer mortality. Compared with daytime workers or those never exposed to night work, ever exposure to night work yielded pooled relative risks of 1.06 (95% CI: 1.03, 1.08) for all-cause mortality, 1.15 (95% CI: 1.03, 1.29) for cardiovascular mortality, and 1.04 (95% CI: 1.00, 1.08) for cancer mortality. Moderate to high between-study heterogeneity was present.
Why it matters
The analysis helps clarify conflicting evidence by demonstrating that night work specifically, rather than shift work in general, is associated with small increases in all-cause, cancer, and especially cardiovascular mortality.
Limits
All included data are observational, leaving findings vulnerable to residual confounding by lifestyle, diet, or socioeconomic differences between shift workers and day workers. Moderate to high heterogeneity was observed across studies. The abstract does not provide dose-response analyses regarding cumulative years or intensity of night shift exposure.
Cited by
- supports Extensive research demonstrates that shift work impairs gastrointestinal health, elevates cancer risk, and reduces longevity.