Working Night Shifts May Increase Likelihood Of Ovarian Cancer

Ovarian cancer research

You may casually assume whatever shift you work has an equal impact on your health, but, before you accept the later shift with slightly higher differential pay, consider the research published in Occupational and Environmental Medicine which suggests working night shifts may increase ovarian cancer risk.

Standard working hours are broken down into three shifts in a 24 hour period. First shift is usually considered 7 am to 3:30 pm, second shift 3:00 pm to 11:00 pm, and third shift is 11 pm to 7 am, give or take an hour on each.

Researchers determined their cancer findings after combining and reviewing 1,101 women with ovarian (epithelial) cancer, 389 with borderline disease (non-invasive ovarian tumors) and a comparison group of 1,832 women without ovarian cancer. All 3,322 participants were between 35 and 74 years of age.

Subjects were questioned about the hours they worked and which shifts. Many were employed as healthcare workers, in food preparation, or administrative support staff. Night shifts averaged between 2.7 and 3.5 years across all three groups of women.

Of those with invasive cancer, 26.6 percent had worked night shifts as well as 32.4 percent with non-invasive cancer and 22.5 percent in the non-cancer comparison group. Night shifts were associated with a 24 percent increase in advanced cancer and 49 percent for early stage compared to those working regular daytime hours.

Approximately 22,000 women are diagnosed with ovarian cancer every year in the United States. Surface epithelial-stromal tumors, also known as ovarian epithelial carcinoma, is the most common type of ovarian cancer. Surface epithelial-stromal tumors are a class of ovarian neoplasms that may be benign or malignant. Tumors of this type are also called ovarian adenocarcinoma.

These types of tumors account for nearly 90 percent of all cases of ovarian cancer. Malignant tumors, cancer prone to metastasize (proliferate to other surrounding cells), account for about 30 percent of all ovarian tumors. Borderline growths are considered non-invasive tumors and respond well to treatment.

Study author Parveen Bhatti, of the Fred Hutchinson Cancer Research Center in Seattle, noted only women 50 and older were significantly more prone to have night shift related ovarian cancer. Still, it was determined, overall, second shift work was allied with a heightened manifestation of both invasive and non-invasive ovarian cancer.

It has been theorized the increased risk for cancers among those who work at night may have to do with melatonin. Melatonin is a hormone secreted by the pineal gland in the brain. It helps regulate other hormones and maintains the body’s circadian rhythm. The circadian rhythm is an internal 24-hour biological clock.

Hormones and circadian rhythms play critical roles in sleep homeostasis. Along with sleep, melatonin governs menstrual cycles. Production of melatonin is higher at night during sleep. When ambient light is detected by photoreceptors in the retina and is relayed to the brain, production of melatonin drops.

Several studies suggest that low melatonin levels may be associated with breast cancer risk. Laboratory experiments have found that low levels of melatonin stimulate the growth of certain types of breast cancer cells, while adding melatonin to these cells slows their growth. Preliminary evidence also suggests that melatonin may strengthen the effects of some chemotherapy drugs used to treat breast cancer. Similar health research has also shown lower levels of melatonin in prostate cancer victims.

The International Agency for Research on Cancer asserts second and third shift work disrupts the body’s natural circadian rhythm, promoting an environment for health problems. Working second or third shift hours can impact a person’s psychological and physiological health, as seen with an amplified occurrence of insomnia, anxiety, and depression.

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