About 15 million Americans work the night shift (or third shift), clocking in after dark and leaving after the sun rises. In 2021, the demand for night shift workers increased as organizations tried to meet booming consumer demand and work through supply chain bottlenecks from the COVID-19 pandemic. Job search website ZipRecruiter reported that postings for jobs requiring overnight shifts were 14 times higher than before the pandemic.

Although there are potential perks to working the night shift — higher pay, less traffic, more flexibility, and less distraction — research shows that long-term rotating shift work (working both shifts during the day and overnight) comes with dangerous health consequences. These may include an increased risk for developing cancer, including various forms of myeloproliferative neoplasms (MPNs).

This article discusses why night shift work can be dangerous to your health, how third shift work may increase your chances of getting MPNs, and ways to minimize the risk if you find yourself working the night shift.

How Night Shift Work Can Cause Health Risks

The most dangerous aspect of night shift work is the disruption it has on sleep schedules and the circadian rhythm. In 2007, the International Agency for Research on Cancer declared shift work that involves a circadian disruption as a probable human carcinogen (cancer-causing agent).

A normal sleep pattern includes sleeping when the sun is down and being active when the sun is up. However, during night shift work, this pattern is reversed. This reversal can cause the body to miss critical signals that help keep the immune system strong.

Someone working the night shift is exposed to artificial light, which is often the main culprit in disrupting circadian rhythms. Specifically, artificial light exposure at night decreases the production of melatonin, a hormone that is triggered during darkness to help us sleep. Another important function of melatonin is to help stop tumor growth and malignancies.

In addition to melatonin suppression, a sleep pattern imbalance can also cause the following negative health outcomes:

• Cardiovascular disease
• Obesity
• Gastrointestinal problems
• Peptic ulcers
• Anxiety
• Depression
• Diabetes
• Chronic fatigue

Night shift workers may also develop lifestyle habits that may increase their risk of developing certain health conditions, including some blood cancers and MPNs. These risky behaviors may include consuming more energy drinks or caffeine, smoking, routinely using aspirin or ibuprofen, and eating an unhealthy diet, which may lead to obesity and a higher body mass index.

Night Shift Work and Myeloproliferative Neoplasms

Although research shows a strong correlation between night shift work and increased risk of certain cancers such as breast cancer, there is inconclusive evidence linking routine shift work to MPNs. MPNs include essential thrombocythemia, polycythemia vera, primary myelofibrosis, and certain types of leukemia.

The number of years a person spends working the night shift is directly correlated with an increased risk of developing cancer. In one study, the risk of MPNs and other blood cancer subtypes increased when a person spent more than 15 years in a nighttime career.

With an increase in demand for night shift workers, more research and clinical trials are needed to study the long-term outcomes of working during the night, especially when it comes to cancer risk and its implications for public health. Research has commonly used female nurses working the night shift as a sample to study the effects of night shift work on different types of cancer, including breast cancer, lung cancer, and colorectal cancer. Other research including men has examined cancer risk, including non-Hodgkin lymphoma and prostate cancer, with inconclusive results.

Working the night shift can harm your physical and mental health, especially when you work these hours for many years. Preventive measures and changes to company policies can help keep workers safe. These changes include:

• Enforcing rules that workers receive an appropriate number of breaks
• Providing healthy and ergonomic (safe and comfortable) working environments
• Encouraging routine cancer screenings and follow-up for night shift workers

Minimizing Your Health Risk

Many jobs and careers that are critical to our health, safety, and convenience are 24/7 operations that require people to work the night shift. Although the dangers of mixing up your sleep schedule and circadian clock are well known, these shifts are not going away. It is important to take steps to protect your health if you work at night, either in the short term or long term.

The best ways to protect your health include:

• Eating a healthy, balanced diet
• Limiting your alcohol consumption
• Getting routine physical activity
• Minimizing caffeine and energy drink intake
• Drinking lots of water

These suggestions are recommended for everyone, no matter what time of day you work. There are also helpful tips specific to people who work the night shift. These recommendations include:

• Blocking out daytime noises with a white noise machine or earplugs
• Eating your meals at the same time each day
• Eating high-protein foods to help you stay alert
• Taking time to relax after work
• Having a light snack before going to bed
• Using blackout shades to mimic nighttime
• Avoiding sleeping pills and other medications that cause drowsiness
• If you are pregnant, working only one night shift per week

If you enjoy working the night shift, or if your career demands it, try to limit the number of years and number of consecutive shifts that you work. This can help you to avoid the long-term health risks associated with disrupting your natural sleep cycle.

You’re Not Alone

If you have myeloproliferative neoplasms, it can help to have the support of others who understand. By joining myMPNteam, you gain a community of more than 2,000 people affected by MPNs. Members come together to ask questions, give advice, and share their experiences with others who understand life with MPNs.

Do you think night shift work contributed to your risk of MPNs? Share your experience in the comments below, or start a discussion on myMPNteam.