Macau Matters | Shift-work dangers

Richard Whitfield

In Macau a lot of people work on shifts – we are all familiar with the associated early morning, mid-afternoon and late evening traffic jams. This poses some special health risks that I suspect we need to manage better in Macau.

The World Health Organization officially classifies night-time shift-work as a possible carcinogen. This finding is based on the results of many large epidemiological studies that have found substantially higher breast, prostrate, uterus and colon cancer rates among night-shift workers. In a world first, the Danish government recently paid workers’ compensation to several women who developed breast cancer after working on night-shift for several years.

Working night-shifts disturbs our circadian rhythm and the quality of our sleep. This is known to adversely affect our immune system and to reduce the natural night-time production of NK cells in our bodies which are known to recognize, attack and kill many types of cancer cells. Sleep deprivation is also known to stimulate our sympathetic nervous system and fight-flight response (so we feel nervous and are easily startled). This stimulates blood flow and body inflammation responses, which some cancers can take advantage of to speed up their growth, and to speed up their spread via metastasis.

Poor and disturbed sleep also leads to several other health problems because it interferes with several bodily repair functions. During sleep our bodies naturally regulate the proper functioning of many of our genes (which are the part of the cells in our bodies that are used as blueprints to make the proteins and other chemicals we need to sustain life).

For example, sleep deprivation stops the production of Growth Hormone which our bodies use to tell its cells to grow and split to repair bodily “wear and tear”. This is an important part of our immune system as well, which is why sick people often just want to sleep (to let their bodies repair themselves).

Furthermore, in separate studies, experimental subjects that were only permitted to have 4 hours of sleep each night for a week before being vaccinated for Flu and for Hepatitis A and Hepatitis B were found to only produce 50% of the anti-bodies of other comparable subjects that were not sleep deprived. Thus prior sleep deprivation may affect the efficacy of vaccinations that help strengthen our immune system.

Similarly, inadequate sleep lowers the concentration of Leptin (which makes us feel satiated) and increases the levels of Ghrelin (which makes us feel hungry) in our bodies. Thus chronic lack of sleep leads to over-eating and poor dietary habits, and thus to obesity and diabetes. It also lowers our energy levels so we do not want to exercise.

Even small amounts of sleep deprivation can have a big impact. It is known that the start of daylight savings time, and its associated 1 hour of sleep loss, is strongly correlated with spikes in heart attack and traffic accident rates.

Some researchers say that good quality and quantity sleep is the essential foundation for a healthy life, along with good dietary practices and regular exercise. Many epidemiological studies have found correlations with sleep and many physical and mental health problems and overall lifespan. In Macau, I believe that we need to put a lot more effort into publicizing the benefits of a good night’s sleep, and how to reduce the deleterious effects of working on night-shift.

Reference: Walker M (2017) Why We Sleep – The New Science of Sleep and Dreams, New York:Penguin Random House