Whether nurses, police officers, or other professionals, an increasing number of people engage in shift work - the practice of working hours outside of a typical day shift. According to new research, this may be contributing to heart disease, certain types of cancer, and a variety of other negative health effects. Could working odd hours actually be bad for your health?  

Heart Disease and Cancer: Modern Pandemics

Heart disease and cancer are two of the most common causes of death in the Western world. The rates of these diseases have been rising almost continuously for the past several decades despite a growing array of medications and treatment options. One American dies every 40 seconds from cardiovascular disease, while almost 40% will be diagnosed with cancer in their lifetime. The combined cost of these diseases adds up to billions of dollars per year. Although there are many treatments that can slow or stop these diseases, prevention and reducing risk are the most important ways to reduce disability and death from these diseases.  

The Importance of a Healthy Circadian Rhythm

Although it may seem surprising, keeping a healthy circadian rhythm with natural sleeping hours may be an important way to reduce both heart disease and cancer rates. A study looking at the health and living conditions of nurses over more than a decade found that those who worked evening or night shifts had an increased risk of several serious diseases, even when controlled for other lifestyle choices and health factors. They also report higher rates of obesity, mental fog, and other health problems.   

Nurses are not the only people affected negatively by shift work. A 2006 study in Japan found that working odd hours, particularly working rotating shifts, was associated with higher rates of ischemic heart disease, the most common cause of cardiovascular death.  

How Shift Work Increases Disease Risk

How can one's working hours increase heart disease and cancer risk? There are multiple explanations. First, melatonin, which is produced in sleeping hours, is an antioxidant that prevents damage to tissues and DNA. When this damage accumulates, cancer and heart disease are common results. People who do not sleep regular hours often have disordered melatonin production, which may reduce their body's ability to repair itself. Second, people who sleep at unusual or changing hours have lower amounts of REM sleep. REM sleep is generally the most restful and also a time when many tissues repair themselves. Losing out on tissue repair repeatedly over years can lead to permanent damage.   

The standard working hours of our past are becoming less common, with less than a quarter of workers in developed nations enjoying this kind of schedule. Our world now operates 24/7, requiring an increased number of workers to keep stores and hospitals open. This appears to have an incredible negative effect on health, particularly on heart disease and cancer risk. Working a job with regular hours may be one of the most important things a person can do to maintain whole body health for a lifetime.   


  1. Shift Work and Health: Current Problems and Preventive Actions. Saf Health Work. 2010 Dec; 1(2): 112–123. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3430894/
  1. American Journal of Epidemiology, Volume 164, Issue 2, 15 July 2006, Pages 128–135,https://doi.org/10.1093/aje/kwj185

Hematology/Oncology (Cancer), Cardiology (Heart)

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