Why does night shift work increase the risk of cancer, diabetes and heart disease?

Since the Industrial Revolution and the development of artificial lighting in the manufacturing and service sectors, shift work has been used to increase productivity and profitability, as well as to provide uninterrupted medical and emergency care.

But work shifts, when you are supposed to sleep and rest, disrupt your normal functions.

More cancer, heart attacks and diabetes

Until the 1990s, little was known about the impact of shift work on health.

Then a landmark study using clinical data from the mid-1990s found that nurses working the night shift were more likely to develop breast cancer. This risk increased with the number of years spent on shift work.

Research has shown that shift work, especially shift work, also increases the risk of heart disease, obesity, type 2 diabetes, dementia, and premature death in general.

It is also associated with decreased vigilance and an increased risk of accidents.

A growing body of evidence points to disruption of the circadian clock caused by being active or waking up at night when we should be sleeping.

Through evolution, living organisms, from bacteria and plants to humans, have acquired clocks to optimize bodily processes in an environment that changes throughout the day. Thus, almost every aspect of behavior, physiology, and metabolism is rhythmically regulated to anticipate these daily changes.

For example, muscle strength, immune system, and cognitive performance are higher during the day, when the body also stores nutrients from food. These functions are reduced at night, when the body begins to use the nutrients stored during this period of fasting.

These daily clocks are present in almost every cell of the body. The central clock in the brain acts as a kind of conduit that is synchronized every day by the light of the environment.

And if that clock is now receiving data from other sources, such as food at night, or if the conductor is distracted by something like lights at night, that synchronization is lost.

This leads to weight gain, type 2 diabetes, high blood pressure and a weakened immune response.

This manifests itself even in low light conditions in the bedroom, for example, on the TV screen.

In animal model studies, this loss of synchrony led to an increase in the incidence of breast cancer and faster tumor growth. It also exacerbated Alzheimer’s symptoms in rat studies.

As in animal models, disruption of normal physiology caused by light at night or feeding at inappropriate times impairs normal organ function, especially the ability to store and use nutrients for an appropriate period of time.

Disruption of circadian rhythms is also associated with a disorder of the autonomic nervous system, which regulates our basic functions, such as breathing or maintaining a heartbeat. This affects the relationship between the brain and surrounding tissues and their proper functioning.

Simulation of shift work has shown an effect on the immune system. This contributes to an increased risk of night shift workers becoming infected, especially COVID-19, and may also play a role in the development of cancer.

Overall, this contributes to increased global susceptibility to many diseases, including diabetes and heart disease.

The circadian clock also plays an important role in the efficacy and toxicity of most drugs, including cancer chemotherapy. A continuous circadian rhythm influences the response to treatment.

What can we do about it?

The first step should be to limit the intermittent work as much as possible. And while people can adjust to work at the “wrong” time to some extent, it’s impossible to adjust to ever-changing schedules.

Numerous experiments studying the effect of lighting have shown that bright light increases nighttime alertness and helps organisms adapt to night work by changing the phase of the circadian clock. However, long-term health effects are yet to be determined.

Controlling and limiting the amount of time people eat seems to be a promising approach that may be beneficial for heart and metabolic health and appears to be compatible with shift work. It also reduced tumor growth in animal breast cancer studies.

Source: Medical Express