Does Working Night Shifts Affect Your Lifespan? What the Evidence Says

Short answer: Working rotating night shifts for many years is linked to a small increase in mortality, mainly from cardiovascular disease, and the risk grows with the number of years. For junior doctors working a few years of nights during training, the absolute risk is very low, but the evidence is a good reason to protect your sleep.

What the largest long term study found

The single most informative study on this question comes from the Nurses’ Health Study in the United States, which followed 74,862 female nurses for 22 years. The researchers compared women who worked rotating night shifts (at least three nights a month alongside day shifts) with women who never worked nights.

The results, published in the American Journal of Preventive Medicine in 2015, were clear but modest. Women who worked rotating night shifts for five or more years had an 11 percent higher risk of death from any cause than women who never worked nights. The increase was driven mainly by cardiovascular deaths, which were 19 to 23 percent higher in long term night shift workers.

There was no significant association with death from cancer overall. The exception was lung cancer mortality, which appeared higher, though the researchers noted this could partly reflect differences in smoking patterns rather than night work itself.

Why does a nursing study matter to doctors? Because it is the best long term data available on rotating night shift work and mortality, and the exposure, rotating nights in a caring profession with high cognitive demands, closely resembles hospital medicine.

Does the risk grow with every extra year?

One of the strongest patterns in the evidence is dose dependence: the longer the exposure to night shift work, the larger the associated risk. A dose response meta analysis of prospective cohort studies, published in the European Journal of Preventive Cardiology in 2018, estimated that each additional five years of shift work was associated with a 4 percent increase in cardiovascular disease mortality.

A more recent systematic review and meta analysis from 2025, covering 23 cohort studies and more than 3.3 million participants, found night shift work associated with a 27 percent higher risk of cardiovascular mortality and a 13 percent higher incidence of cardiovascular disease overall. A separate meta analysis by Torquati and colleagues reported an approximately 22 percent higher cardiovascular mortality among shift workers compared with non shift workers.

The pattern is consistent with what epidemiologists expect from a genuine biological effect rather than a statistical fluke: small per year increments that compound over a working lifetime.

Why would night work shorten life at all?

The central mechanism is circadian disruption. Humans are diurnal animals: our physiology is organised around a roughly 24 hour internal clock that expects activity and feeding during the day and sleep at night. Night shift work forces behaviour into direct conflict with that clock. Core body temperature, cortisol rhythms, blood pressure dipping and glucose tolerance all follow circadian patterns, and working through the night misaligns them.

Several downstream effects follow from that misalignment. Sleep becomes shorter and more fragmented: night shift workers typically sleep less during the day than day workers sleep at night, and the sleep they get is lighter. Chronic sleep restriction is independently associated with hypertension, obesity, type 2 diabetes and metabolic syndrome. Blood pressure shows a blunted night time dip in shift workers, and impaired glucose tolerance has been demonstrated after even short periods of circadian misalignment in laboratory studies.

None of this is speculative biology: each of these pathways is supported by experimental and observational evidence, and together they provide a plausible chain from night work to the cardiovascular mortality seen in the cohort studies.

Is cancer part of the story?

In 2019, the International Agency for Research on Cancer reviewed the evidence on night shift work and cancer. It classified night shift work as “probably carcinogenic to humans” (Group 2A). The classification was based on limited evidence in humans, mainly for breast, prostate and colorectal cancers, together with sufficient evidence in experimental animals and strong mechanistic evidence involving circadian disruption.

An updated meta analysis of prospective cohort studies, published in 2022, added numbers to the cancer question. Across 31 cohort studies and 9.3 million participants, night shift work was linked to a 2.9 percent higher incidence of breast cancer, rising to 8.6 percent with more than ten years of exposure.

These are small relative increases, and relative risk needs context. A 3 percent increase in the incidence of a disease is very different from a 3 percentage point increase in absolute risk. But the IARC classification means the cancer question deserves to be taken seriously alongside the stronger cardiovascular evidence.

What does this mean for junior doctors specifically?

A direct answer requires honesty about what the evidence does and does not cover. The strongest mortality data come from nurses working rotating nights for many years, often decades. Junior doctors typically work intense night rotas for a few years during foundation and specialty training, not for twenty years. The absolute risk from a few years of nights in your twenties is very low, and no study has directly measured mortality in doctors by years of night shifts.

That does not mean the findings are irrelevant. The cardiovascular and metabolic pathways implicated, circadian disruption, fragmented daytime sleep, impaired glucose tolerance, apply to anyone working against their body clock. And junior doctors face an additional, more immediate risk profile: fatigue related errors, needlestick injuries, road traffic accidents after nights, and effects on mental health. The long term mortality data is one more reason to treat sleep protection as a professional duty, not a luxury.

There is also a short term dimension that matters more to trainees than the long term mortality figures. Cognitive performance after a night shift resembles performance under the influence of alcohol, and clinical decision making, procedural skill and empathy all degrade with sleep loss. Protecting sleep on nights is about patient safety today as well as your own health decades from now.

Can you work nights more safely?

No rota redesign or sleep trick can make night work biologically neutral, but the evidence points to several ways of reducing the harm.

Protect your daytime sleep as the single most important habit. The NHS advises that most healthy adults need around 7 to 9 hours of sleep a night, and that target still applies to daytime sleep after nights. Make your bedroom dark (blackout blinds or an eye mask), cool and quiet (earplugs if needed), and tell the household your sleep is protected time.

Keep a consistent sleep window where you can. Going to bed and getting up at roughly the same times, even on days off, stabilises the circadian system. Anchor sleep, a core block of at least 4 hours at the same time each day with top up naps around it, is a practical compromise when full consistency is impossible.

Use light deliberately. Bright light during the night shift helps alertness, while bright daylight on the morning commute home pushes the clock in the wrong direction; sunglasses for the journey home are a simple, evidence backed habit.

Time your caffeine and your naps. Caffeine early in the shift supports alertness; caffeine in the last few hours before daytime sleep will fragment it. A planned nap of 20 to 40 minutes during the shift, where the rota and workload allow, measurably improves performance.

Plan recovery after a run of nights. The transition back to days deserves at least one full sleep opportunity, and safety critical tasks, including driving home after the last night, should be treated with the same caution as the shift itself.

Finally, keep perspective on the numbers. An 11 percent relative increase in all cause mortality after five or more years of rotating nights is a real signal, but it is not a fate. Most of the risk is modifiable through the same habits that protect health generally: not smoking, staying active, eating well and keeping blood pressure and weight in check.

The bottom line

Does working night shifts affect your lifespan? The best available evidence says yes, modestly, and mainly through cardiovascular disease, with the risk compounding over years of exposure. Night shift work is also classified as probably carcinogenic to humans, with small increases in breast cancer incidence at longer exposures. For junior doctors, a few years of nights carry very low absolute risk, but the evidence is a strong argument for protecting daytime sleep, using light and caffeine strategically, and treating recovery as non negotiable.

Related reading

Frequently asked questions

Does working night shifts shorten your life?

Long term studies link rotating night shift work to a modest increase in mortality. In the Nurses’ Health Study, women who worked rotating night shifts for five or more years had an 11 percent higher risk of death from any cause and a 19 to 23 percent higher risk of cardiovascular death than women who never worked nights. The risk grows with years of exposure.

How many years of night shifts raise mortality risk?

The elevated risks in the major studies appear from around five years of rotating night shift work onwards. Meta analyses show a steady dose response: roughly 4 percent more cardiovascular mortality risk for each additional five years of shift work. A few years of nights during medical training sits well below the exposure levels where the clearest signals were found.

Do night shifts cause cancer?

The International Agency for Research on Cancer classifies night shift work as “probably carcinogenic to humans” (Group 2A), based on limited human evidence for breast, prostate and colorectal cancers. A 2022 meta analysis of 31 cohort studies found night shift work linked to a 2.9 percent higher incidence of breast cancer, rising to 8.6 percent with more than ten years of exposure.

Are permanent night shifts healthier than rotating shifts?

The evidence does not give a clean answer. Rotating shifts repeatedly disrupt the circadian system, while permanent nights allow partial adaptation but never full alignment with a diurnal biology, and they carry social and mental health costs. Most of the mortality evidence comes from rotating shift workers, so comparisons rest on weaker data.

How can junior doctors protect their health on night shifts?

Protect daytime sleep first: a dark, cool, quiet bedroom and a consistent sleep window. The NHS recommends seven to nine hours of sleep for adults. Use bright light during the shift and sunglasses on the morning commute home, time caffeine early in the shift, take a planned nap where possible, eat at consistent times, and allow proper recovery sleep before driving or safety critical tasks after a run of nights.

Sources

  1. Gu F et al. Total and cause specific mortality of U.S. nurses working rotating night shifts. American Journal of Preventive Medicine. 2015. DOI: 10.1016/j.amepre.2014.10.018 (PMID: 25576495). Nurses’ Health Study: 74,862 women, 22 years follow up; rotating night shift work for five or more years linked to 11 percent higher all cause mortality and 19 to 23 percent higher cardiovascular mortality.
  2. Dose response meta analysis of prospective cohort studies on shift work duration and cardiovascular disease morbidity and mortality. European Journal of Preventive Cardiology. 2018. Each additional five years of shift work associated with a 4 percent increase in cardiovascular disease mortality (RR 1.04).
  3. Systematic review and dose response meta analysis of 23 cohort studies on night shift work and cardiovascular disease. Frontiers in Public Health. 2025. More than 3.3 million participants; night shift work associated with 27 percent higher cardiovascular mortality (RR 1.27) and 13 percent higher cardiovascular disease incidence.
  4. Night shift work, breast cancer incidence, and all cause mortality: an updated meta analysis of prospective cohort studies. Sleep and Breathing. 2022 (PMID: 34775538). 31 cohort studies, 9.3 million participants; breast cancer incidence 2.9 percent higher overall, 8.6 percent higher with more than ten years of exposure.
  5. IARC Monographs Volume 124: Night Shift Work. International Agency for Research on Cancer. 2 June 2020. Night shift work classified as “probably carcinogenic to humans” (Group 2A) on limited human evidence (breast, prostate, colorectal cancers), sufficient animal evidence and strong mechanistic evidence. https://www.iarc.who.int/news-events/iarc-monographs-volume-124-night-shift-work/
  6. NHS. Sleep problems: how much sleep do adults need? “Most healthy adults need around 7 to 9 hours of sleep a night.” https://www.nhs.uk/every-mind-matters/mental-health-issues/sleep/
  7. Torquati L et al. Shift work and the risk of cardiovascular disease: a systematic review and meta analysis including dose response relationship. Scandinavian Journal of Work, Environment and Health. 2018. Shift workers had approximately 22 percent higher cardiovascular mortality (RR 1.22) than non shift workers.

This article is for information only and is not medical advice. If night work is affecting your health, speak to your GP or your occupational health department.