A study in China collating 61 studies has found a link between night shift workers and certain types of cancer.
I find this interesting because I recently read Matthew Walker’s book “Why We Sleep” and he mentions 8 hours sleep per night is absolutely necessary for good health.
The increase may come from the lymph system not removing cells that are due for recycling (about every 6 weeks) which occurs at night, instead they fester and can turn cancerous.
Two separate hormones are at play here, 1) Melatonin, released by the pineal gland which builds up gradually as darkness falls to begin the scavenging process and 2) Seratonin which increases with daylight.
Two other major factors in cancer prevalence are Vitamin D and high meat consumption. Vitamin D is a essential to maintain a healthy immune system, and meat is extremely healthy when eaten in the right quantities, but not when out of proportion to vegetables.
Obesity is also a known factor, thought to be the second major cause of cancer in the UK.