Breast cancer risk and epigenetic effects of the rotating night shift work and lifestyle.

Polish cross-sectional study

Nurses were selected from the Local Registry of the Chamber of Nurses and Midwives in Lodz. Nurses and midwives, aged 40 to 60 years and currently working, were eligible for the study. 725 women (84% of the eligible) agreed to participate in the study, including 354 working rotating night shifts and 371 nurses working only during the day (for details see Peplonska et al 2012).
A structured questionnaire was administered during in-person interviews, and occupational history data and information on potential confounders were collected. Body weight, height and hip and waist circumferences were measured. 705 women provided blood samples, from which DNA was extracted. The occupational data collected included information on both current work situations and every previous job performed for at least half a year. Additionally data were collected on sleep and work using one week diary preceding blood collection.