The longer you work night shifts, the higher your cardiovascular risk — switch jobs if you can
People who work night shifts develop cardiovascular disease about 13% more often than those who don’t, and cardiovascular-related deaths are about 27% higher. The longer you work nights, the worse it gets: for every additional five night shifts, cardiovascular disease risk rises by roughly 7%. So, when you calculate this over years, it makes sense to switch jobs early on. As for cancer and night shifts, the evidence is far weaker than commonly believed. A meta-analysis of 12 studies involving 12,132 breast cancer cases found only a 5% higher risk among night-shift workers (RR 1.05, 95% CI 0.96–1.14). For those who worked night shifts for 20 years, the risk rose to 25% (RR 1.25, 1.01–1.55), but after correcting for publication bias this figure became non-significant and essentially close to 1; the authors concluded this link “is far from established.” Another long-term study of Chinese men followed for 16.1 years found no overall link between night shifts and cancer; only pancreatic cancer risk rose about 59% (HR 1.59, 1.09–2.31) among those who worked night shifts for 11–20 years. The absolute number of pancreatic cancer cases in this group was 8,202. Therefore, this discussion focuses on cardiovascular risk, not cancer.
Switching jobs or changing roles may mean a lower salary a…
A pooled analysis of 23 studies — all observational, no subgrouping — shows that night-shift workers face a ro…
Switching jobs or changing roles may mean a lower salary and the loss of night-shift allowances. Job hunting takes time and requires a firm decision. If you factor this cost in when choosing a job, it effectively becomes zero.
A pooled analysis of 23 studies — all observational, no subgrouping — shows that night-shift workers face a roughly 13% higher risk of cardiovascular events (RR 1.13, 95% CI 1.10–1.16). Cardiovascular-related deaths are about 27% higher (RR 1.27, 1.18–1.36). Over time, each extra five night shifts adds roughly 7% to cardiovascular disease risk (RR 1.07, 1.04–1.09) and about 5% to cardiovascular deaths (RR 1.05, 1.03–1.06). Specific conditions show similar trends: coronary heart disease incidence rises about 22% (RR 1.22, 1.16–1.28), as does coronary death risk (1.22, 1.10–1.36). Ischemic heart disease death risk climbs about 39% (1.39, 1.06–1.84), while stroke death risk increases about 49% (1.49, 1.04–2.12). Stroke incidence, however, shows no significant change (RR 1.06, 0.95–1.18).
Xi J, Ma W, Tao Y, 等 (2025). Association between night shift work and cardiovascular disease: a systematic review and dose-response meta-analysis. Frontiers in Public Health. https://doi.org/10.3389/fpubh.2025.1668848；Esposito G, Bravi F, Santucci C, 等 (2025). Night shift work and breast cancer risk in healthcare workers: a systematic review and meta-analysis. Occupational Medicine. https://doi.org/10.1093/occmed/kqaf040；Shen QM, Li ZY, Tan YT, 等 (2026). Night shift work and risk of total and site-specific cancer: results from a prospective cohort study among Chinese men. Scandinavian Journal of Work, Environment & Health. https://doi.org/10.5271/sjweh.4290；Czeisler CA, Johnson MP, Duffy JF, 等 (1990). Exposure to bright light and darkness to treat physiologic maladaptation to night work. New England Journal of Medicine, 322(18), 1253-1259. https://doi.org/10.1056/NEJM199005033221801
Open source linkAll these studies are purely observational and do not adjust for key factors like smoking, weight, or income — differences that naturally exist between night-shift workers and others. Cancer and night shifts: the evidence is much weaker than popular belief suggests. A meta-analysis of 12 studies involving 12,132 breast cancer cases found only a 5% higher risk among night-shift workers (RR 1.05, 95% CI 0.96–1.14). For those who worked night shifts for 20 years, the risk rose to 25% (RR 1.25, 1.01–1.55), but after correcting for publication bias this figure became non-significant and essentially close to 1; the authors concluded this link “is far from established.” Another long-term study of Chinese men followed for 16.1 years found no overall link between night shifts and cancer; only pancreatic cancer risk rose about 59% (HR 1.59, 1.09–2.31) among those who worked night shifts for 11–20 years. The absolute number of pancreatic cancer cases in this group was 8,202. Therefore, this discussion focuses on cardiovascular risk, not cancer. Not everyone must quit night shifts — you should weigh the yearly cost-benefit yourself. For those already working nights, several steps can help: quit smoking (see Section 1), control blood pressure and cholesterol (Section 12), and make up lost sleep properly (Section 39). Two additional strategies are worth trying: eat mainly during daytime hours and use bright light during shifts while strictly avoiding light at night to reset your circadian rhythm. The latter is the only proven method to shift circadian timing; ordinary indoor lighting leaves the rhythm unchanged even after six night shifts, but exposure to 7,000–12,000 lux during shifts plus near-total darkness by day can reset it in just four days. Crucially, bright nighttime light, strict daytime darkness, and wearing sunglasses on the way home are all essential — missing any one of them negates the effect. Neither strategy has been shown to lower cardiovascular risk; returning to a daytime routine on days off also resets the rhythm. Full details on exact figures, sources, and how the body tracks time can be found in docs/生物钟和夜班.md.