In the largest study of its kind, new research links long-term night shift work to an increased risk of haematopoietic cancer.
Haematopoietic cancers, such as leukaemia and lymphoma, affect immune system cells in the blood, bone marrow, lymph, and lymphatic system. In the United States, a new diagnosis of haematopoietic cancer is made every three minutes, with this type of cancer accounting for 10% of all new cancer diagnosis.
Every type of haematopoietic cancer comes with its own risk factors, however, in most cases the cause is unknown. In an attempt to gain a greater understanding of the risk factors, researchers recently investigated the association between rotating night shift work and the risk of developing haematopoietic cancer. Published in the JNCI Cancer Spectrum a large research study interpreted data from the United States Nurses’ Health Study and Nurses’ Health Study II, which are ongoing studies of female registered nurses. Over 120,000 participants were enrolled in the first Nurses’ Health Study between the ages of 30-55 years and over 115,000 in Nurses’ Health Study II between the ages of 25-42 years.
The researchers found that nurses who work a long duration of rotating night shift work (over 15 years) had a greater risk of developing haematopoietic cancer.
This raises the question as to how night shift work can be associated with greater cancer risk. In 2019, the International Agency for Research on Cancer classified night shift work as a probable carcinogen (a carcinogen is any substance or radiation that promotes the formation of cancer) to humans. Previous studies have demonstrated the carcinogenicity of altering the body clock and light-dark schedule. It is speculated that night shift work may suppress melatonin, which regulates the sleep-wake cycle and is a powerful antioxidant (protecting cells from harmful free radicals). In addition, people working in a longer duration of night shift work are more likely to be older, have a higher body mass index, higher levels of energy intake, more likely to smoke, and more likely to use certain medications, which may all have an influence.
There are a number of occupational, environmental, lifestyle, and physiological factors that may explain the connection between night shift work and a greater incidence of haematopoietic cancer. However, the results from this study are advised to be interpreted with caution as more research is needed to build an understanding of the association between rotating night shift work and haematopoietic cancer.
Written by Helen Massy BSc
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