Breast cancer in healthcare shift-and night-workers – preliminary results of a case control study and risk management

Shift work, in particular the night shift, has a significant impact on health, especially increasing the onset of digestive, cardiovascular and oncological pathologies. In 2019, IARC confirmed the shift and night work as a probable carcinogen for humans (Group 2A), due to its association with breast cancer. Mechanisms involved are genetic predisposition, de-synchronization of circadian rhythms due to sleep losses with alterations in the cell cycle’ regulation and immunological deficiencies. Nevertheless, epidemiological evidences are still limited. The purpose of this case-control study was to estimate breast cancer risk due to night shift work in health settings also considering some possible confounders such as personal and organizational factors. Data were collected by a dedicated questionnaire investigating shift work exposure, along with other personal risk factors for breast cancer. Overall 433 subjects (79 cases and 354 controls) were recruited from two large health settings in central Italy. The preliminary results showed an increased risk of developing breast cancer in female workers who have used oral contraceptives for a period from 5 to 20 years, compared to the subpopulation that does not use it (OR 2.70, IC 95% 1.21 – 6.01). No significant association was found with shift work exposure. The prolonged use of oral contraceptives as birth control method could have relevant health and organizational implications in health care settings. Further efforts are warranted to clarify the role shift work and contraceptive use on the development of breast cancer.