【By Cai Wenying and Ning Weiyu】

The International Agency for Research on Cancer (IARC), a branch of the World Health Organization, recently classified night shift work as a potential carcinogen. Domestic experts indicate that working night shifts may disrupt hormone and melatonin secretion, weaken immunity, and increase cancer risk, advising people to minimize overnight work.

### Latest Report

Published in the December issue of *The Lancet*, the report newly identifies night shift work as a human carcinogen. The American Cancer Society suggests that night shifts may soon be listed among "known and probable carcinogens."

### 10% of Domestic Workers Rotate Night Shifts

Steven Stevens, a professor of cancer epidemiology at the University of Connecticut Health Center, was among the first to link night shifts to cancer. His 1987 study found that night work increased breast cancer risk. Recent studies also suggest long-term female night shift workers face higher breast cancer rates, while animal experiments show disrupted sleep cycles lead to faster cancer progression and mortality. Other research indicates male night shift workers have a higher risk of prostate cancer.

However, most studies focus on nurses or airline crews, necessitating broader research. If confirmed, this could affect millions globally, with an estimated 20% of workers in developed nations working night shifts. In Taiwan, Labor Ministry statistics show about 10% of workers rotate night shifts.

Peng Wang-Jia Kang, director of the National Health Research Institutes' Cancer Research Center, notes that night work disrupts circadian rhythms, particularly hormone secretion. Chang Chin-Chien, chairman of the Cancer Society, explains that irregular sleep cycles disturb the biological clock, weaken immunity, and alter melatonin and hormone levels. Ding Qi-Wen, vice superintendent of Landseed Hospital, adds that melatonin, secreted by the pineal gland (highlighted in red), peaks at night and drops during the day. Artificial light during night shifts suppresses its production, potentially leading to abnormal cell replication and higher cancer risk.

### Health Ministry: Not Yet Confirmed

Deputy Director-General Chao Kun-Yu of the Health Promotion Administration urges calm, as the link remains unproven. However, flight attendant Mr. Lin shares, "Night shifts already cause insomnia—now I learn they might raise cancer risk too."

### Melatonin and the Biological Clock

Melatonin, produced by the pineal gland, regulates sleep, supports immunity, and inhibits cancer cell growth. Disrupted rhythms may lead to faulty cell division.

### Tips for Night Shift Workers

- Sleep in complete darkness (e.g., use blackout curtains during daytime rest).
- Maintain a consistent routine; avoid caffeine during shifts.
- Moderate exercise helps adjust to shift changes and boosts alertness.
- Rotate shifts clockwise: day → evening → night.
- Prepare for schedule changes by gradually adjusting sleep times 2–3 days before switching shifts.
- Chronic disease patients (e.g., hypertension, diabetes) should consult doctors to adjust medication timing with shift changes.

*Sources: Cancer Society Chairman Chang Chin-Chien, Landseed Hospital VP Ding Qi-Wen*Consult with a physician to discuss whether to enhance screening for specific diseases or cancers.

Source: http:/ / tw. nextmedia. com/ appl……id/ 30028790/ IssueID/ 20071201