Characteristics of studies on breast cancer regarding definitions of non-day time work
Reference. Country, state | Study design | Breast cancer cases | Study population | Primary exposure | Sources of primary exposure information | Non-day time exposure definition | Reference group | Reported exposed categories |
Tynes et al,8 Norway | Nested case-control | 50 | Female naval radio-telegraph operators | Light at night, radio frequency fields, low frequency fields | Database with job history on certified telegraph operators from Norwegian Telecom. Shift work and travel through time zones was assessed from job history by a shipping journalist and a researcher | Frequent present in radio room both at night and during the day | No shift work |
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Hansen,10 Denmark | Population based nested case-control | 7035 | Female employees | Night work | Job exposure matrix based on survey (1976) on working condition, linked to population registry (job title) and pension fund registry data (duration of employment since 1964 on company and trade level) | Working at least half a year at least 5 years prior to reference date in trades where at least 60% of survey responders had nighttime schedules | Working in trades where less than 40% of survey responders had nighttime schedules | Overall > 6 years |
Davis et al,6 USA | Case-control | 763 | Females | Light at night: sleep habits, bedroom lightning, shift work | In-person interview of all jobs held for 6 months or longer | Graveyard shift: beginning work after 19:00 and leaving work before 9:00 | Never worked graveyard shift |
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Schernhammer,11 USA | Prospective cohort | 2441 | Nurses participating in Nurses Health Study I | Night work as a surrogate of light at night | Postal questionnaire in 1988 | Rotating night shifts: Years in total worked at least three nights per month in addition to days or evening in that month: never, 1–2, 3–5, 6–9, 10–14, 15–19, 20–29, ≥ 30 years. | Never working on rotating night shifts |
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Schernhammer,12 USA | Prospective cohort | 1352 | Nurses participating in Nurses Health Study II | Rotating night shift work | Postal questionnaire in 1989 (baseline), updated in 1991, 1993 and 1997. Information obtained retrospectively in 2001 for the periods 1993–1995 and 1997–1999. | Rotating night shifts: total months worked for at least three nights per month in addition to days or evening in that month: none, 1–4, 5–9, 10–14, 15–19, 20–29, >=20 months. Also information on permanent night shift for ≥6 month. | Never working on rotating night shifts |
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Lie et al,14 Norway | Nested case-control | 537 | Nurses | Night work | Job exposure matrix based on information from the Norwegian board of Health's registry on nurses and censuses from 1960, 1970 and 1980 | Nurses working at infirmaries (hospitals) | Other work sites than infirmaries |
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Schwartzbaum, et al,13 Sweden | Retrospectiv cohort | 70 | Female participants from censuses in 1960 and 1970 | Shift workers | Job exposure matrix based on survey (1977–1981) and occupational information from census | Occupation-industry combinations in which at least 40% of the workers had a rotating schedule with three or more possible shifts per day or had work hours during the night (any hour between 0100 and 0400) at least 1 day during the week | Occupation- industry combinations in which < 30% of the workers had shift work (as defined to the left) |
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Pesch et al,7 Germany | Population based case-control | 892 | Gene Environment Interaction and Breast Cancer (GENICA) participants | Night shift work | Personal interview of occupational history. Subsequent telephone interviews on shift work | Working the full-time period between 24.00 and 05:00 h (ILO definition) for at least 1 year | Ever employed, but never in shift work |
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O'Leary et al,9 USA | Case-control | 487 | Long Island Breast Cancer Study Project participants, who had lived in the same residence for 15 years or longer | Light-at-night exposure from shift work and at home | In-home interview obtaining information on all jobs held for 6 months or longer for the last 15 years. | Frequency (days per week, months or years) and type of shift work for each job: Evening work (starting afternoon and ending as late as 2:00) Overnight work (starting as early as 19:00. and continue until the following morning) | Participants who had never held jobs involving shift work |
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