Table 2.

Characteristics of the selected (nested) case–control studies on breast cancer and night-shift work

Author	Sample size Case/control	Exposure data source	Adjusted confounders	Definition of night shift	NSW category	Quality score
Hansen and Lassen [20]	218/899	Nationwide pension fund and Danish military’s company registration	HRT, number of childbirths, age at menarche, length of education, occasional sun-bathing, tobacco smoking status	Working during hours beginning after 17:00 and ending before 9:00 for at least 1 year, not including overtime	Short/long	High
Hansen and Stevens [58]	310/1240	Danish nurses association	Age, family history of BC, MHT, number of mammograms	Graveyard shifts which worked after midnight (about 8 h of work between 19 and 9) for at least 1 year	Short/long	High
Li et al. [21]	1709/4780	Factory records (80%), interviews (20%)	Parity, live births, BF, alcohol	Working at least once per week for at least 6 months between midnight and 6 a.m	Short/long	Moderate
Tynes et al. [55]	50/259	Telecom registry	Duration of employment, age, and age of first birth	Years on ships known to involve night shift work and cross time zones	Short/long	Moderate
Linnersjo et al. [57]	16/174	Airline archives	None	––-	Short	Moderate
Rafnsson et al. [56]	35/140	Employment records	Age, age at first childbirth, live births	Employed full-time ≥ 5 years; frequent long distance flights due to remote Iceland location	Short	Moderate
Hansen [61]	6281/6024	Nationwide Pension Fund	Age, age at first and last childbirth, parity, SES	≥ 6 months employment in a trade where ≥ 60% of randomly surveyed women worked at night	Short	High
Fritschi et al. [22]	1205/1789	Western Australian (WA) Cancer Registry	Age, reproductive history, alcohol intake, smoking, PA and sleep, SES, remoteness of residence, family history of BC	Working for any number of hours between midnight and 0500 h	Short/long	High
Menegaux et al. [59]	1232/1317	French departments of ‘‘Coˆte d’Or’’ or ‘‘Ille-et-Vilaine’’	Age, age at menarche, age at first full-term pregnancy, parity, MHT, family history of BC in first-degree relatives, BMI, alcohol consumption, and tobacco consumption	Working for at least 1 h between 11:00 pm and 5:00 am during all or part of each job	Short	High
Grundy et al. [62]	1034/1179	BC Cancer Registry (Vancouver), Hotel Dieu Breast Assessment Program (Kingston)	Age, ethnicity; household income; education; menopausal status; use of fertility drugs, OC, non-steroidal anti-inflammatory drugs (NSAIDs), antidepressants and HRT; reproductive factors including ever having been pregnant, number of pregnancies, age at first birth, BF and age at first mammogram; family history of BC among first-degree relatives; lifestyle factors, including smoking status, pack-years smoking, lifetime alcohol consumption; and BMI	≥ 50% of time was reported to have been spent on evening and/or night shifts, capturing both rotating and permanent night shift schedules	Short/long	High
Pesch et al. [65]	857/892	Telephone interview	Age, family history, HRT, Mammograms	Working the fulltime period between 24:00–05:00 h	Short/long	High
O'Leary et al. [60]	576/585	In-person occupational history	Age, live births, family history, education, benign breast disease	Overnight shift which could start as early as 7:00 p.m. and continue until the following morning	Short	High
Davis et al. [63]	763/741	In-person occupational interview	Parity, family history, OC use, recent HRT	Graveyard shift which began after 7:00 PM and leaving work before 9:00 AM	Short	High
Papantoniou et al. [64]	1708/1778	MCC-Spain Study	Age, family history, education, marital status, BMI, Tobacco smoking, PA, sleep habits, diet habits, Menopausal status, Parity, age at first birth, BF, ever OC, ever hormonal therapy, past sun exposure	Night work was defined as a working schedule that involved partly or entirely working between 00:00 and 6:00 a.m. at least three nights per month. This definition included overnight, late evening (end after 00:00) and early morning (start before 6:00) shifts	Short/long	High
Santi et al. [67]	743/775	Questionnaire	Age, family history, level of education, OC use, alcohol consumption, number of births, and age of first menstruation	Nurses were classified as night-shift workers if they worked in hospitals	Short/long	High
Rabstein et al. [66]	857/892	GENICA (Gene–ENvironment Interaction and breast CAncer)	Family history of BC, HRT, number of mammograms, and estrogen receptor status	Ever having worked in night shifts for ≥ 1 year and working the fulltime period between 24:00–05:00 h	Short/long	High
Lie et al. [68]	172/474	Cancer Registry of Norway	Age at diagnosis, period of diagnosis, parity, family history of BC in mother or sister, hormonal treatment in the previous 2 years before diagnosis, and frequency of alcohol consumption at the time of diagnosis	Work between 12 pm and 6 am	Short/long	High
Truong et al. [16]	1126/1174	CECILE study	Age, study area, age at menarche, age at first full-term pregnancy, parity, MHT, BMI, alcohol consumption, and tobacco consumption	Work for at least 1 h between 1100 and 0500 h during all or part of each job period	Ever/short	High
Pham et al. [69]	1721/1721	Questionnaire and face to face interview	Age, educational level, number of pregnancies, age at birth of first child, body mass index, age at menarche, alcohol consumption, smoking, use of female hormone treatment, and family history of breast cancer in first degree relatives	Ever having worked in night shifts regularly between 9:00 pm and 8:00 am for at least 2 months in their lifetime	Short/long	High

NSW night shift work, HRT hormone replacement therapy, BC breast cancer, MHT menopausal hormone therapy, BF breastfeeding, PA physical activity, SES socioeconomic status, BMI body mass index