Table 2 Case-control studies of night work and breast cancer

Tynes et al.

(1996) [27]

Norway

Nested case-control study of a cohort of 2619 female radio and telegraph operators enrolled 1920–1980, with follow-up 1961–1991; 50 cases and 4–7 matched (year of birth) controls

Collected detailed job histories from Norwegian seamen registry; “Work at night with exposure to artificial light?” From cases and controls, detailed information on job histories on ships, as well as shift work and travel through time zones was collected

Aged < 50

None

1.0 (ref)

<  3.1 years.

0.3 (0.1–1.2)

>  3.1 years

0.9 (0.3–2.9)

P for trend

0.97

Aged 50+

None

1.0 (ref)

<  3.1 years

3.2 (0.6–17.3)

>  3.1 years

4.3 (0.7–26.0)

P for trend

0.13

Hansen

(2001) [20]

Denmark

Nested case-control study with

follow-up 1964–1999; 7565 cases and 1:1 matched controls (year of birth and sex)

Individual employment histories were obtained from files of national pension funds

All night work combined in trades with > 60% night work

1.5 (1.3–1.7)

Employed > 6 years

1.7 (1.3–1.7)

Nurses

1.3 (1.1–1.4)

Davis et al.

(2001) [21]

USA

Cancer register-based case–control study; 813 cases (1992–1995) and 793 matched (5-year age groups) controls identified by random-digit dialing

Information on sleeping habits, light exposure, lifetime occupational history obtained from in-person interviews; night workers defined if ≥1 graveyard shift/wk. (8 h) in 10 years before diagnosis of cancer

Years worked

≥ 3 nights/wk.

None

1.0 (ref)

<  1

1.2 (0.6–2.3)

1–3

1.4 (0.7–2.8)

3–4.6

0.6 (0.3–1.5)

4.7+

2.3 (1.2–4.2)

P for trend

0.01

Lie et al.

(2006) [22]

Norway

Nested case-control study of the cohort of 44,835 Norwegian nurses; 537 cases (1960–1982) and 1:4 matched (year of birth) controls

Total work history reconstructed from occupational information for nurses from the registry censuses of the Norwegian Board of Health in 1960, 1970, and 1980

Years night work

0

1.0 (ref)

1–14

0.95 (0.67–1.33)

15–29

1.29 (0.82–2.02)

30+

2.21 (1.10–4.45)

P for trend

0.01

O’Leary et al.

(2006) [29]

USA

Case-control study of 576 cases (1996–1997) and 585 1:1 matched (age in 5-year age groups) population-based controls

Occupational history since age 16, and residential light-at-night exposures (e.g., sleep hours, frequency of turning on lights during night, length of time light was on) from in-person interviews

Any evening or overnight shift work

1.04 (0.79–1.38)

Any evening shift work only

1.21 (0.90–1.64)

Any overnight shift work only

0.55 (0.32–0.94)

Pesch et al.

(2010) [30]

Germany

GENICA: a population-based case-control study conducted among women from the Greater Region of Bonn, Germany

Night work was defined as working full-time between 24.00–05.00 h

Never

1.0 (ref)

1–4 years

0.64 (0.34–1.24)

5–9 years

0.93 (0.41–2.15)

10–19 years

0.91 (0.38–2.18)

20 years and more

2.49 (0.87–7.18)

Lie et al.

(2011) [26]

Norway

Nested case-control study within a cohort of 49,402 female nurses;

699 cases and 895 controls

“Night work” includes working

periods in both rotating and permanent night schedules, and includes the work of permanent night workers

Never night work

1.0 (ref)

1–11 years

1.2 (0.9–1.5)

12 years

1.3 (0.9–1.8)

P for trend

0.17

Hansen et al.

(2012) [23]

Denmark

Nested case-control study within a nationwide cohort of Danish nurses (N = 91,140), including detailed information on lifetime shift-work and potential confounders

Information on shift work obtained from interviews; Day work defined as working from 6 or 7 to 15 or 16, evening work from 15 or 16 to 23 or 24, and night work from 23 or 24 to 7 or 8

Day-evening only

1.0 (ref)

1–4 years of night work

1.5 (0.99–2.5)

5–9

2.3 (1.4–3.5)

10–19

1.9 (1.1–2.8)

≥ 20

2.1 (1.3–3.2)

Hansen et al.

(2012) [24]

Denmark

Nationwide case-control study

nested within a cohort of 18,551 female military employees born in 1929–1968

Information on shift work, sun exposure habits, diurnal preferences, and other potential confounders

Never

1.0 (ref)

1–5.9 years

0.9 (0.4–1.7)

6–14.9 years

1.7 (0.9–3.2)

15 years and more

2.1 (1.0–4.5)

P for trend

0.06

Fritschi et al.

(2013) [28]

Australia

Case control study of cases from the population-based Western Australian (WA) Cancer Registry, with 1205 incident cases and 1789 frequency age-matched controls

Information on shift work obtained from telephone interviews, with levels of night work being

high: job involved > 4 nights forward rotation or > 6 nights backward rotation, medium: 3–4 nights forward or 4–6 nights backward rotation, or low: 3 nights backward rotation

No rotation

Ever

<  10 years

10–20 years

>  20 years

1.0 (ref)

1.16 (0.97–1.38)

1.25 (1.00–1.56)

1.09 (0.79–1.50)

1.02 (0.71–1.45)

Grundy et al.

(2013) [25]

Canada

A case-control study

from 2005 to 2010

Case definition: where ≥50% of time was reported to have been spent on evening and/or night shifts, capturing both rotating and permanent night shift schedules

No shifts

1.0 (ref)

0–14 years

0.95 (0.79–1.16)

15–29 years

0.93 (0.67–1.30)

>  30 years

2.21 (1.14–4.31)

Menegaux et al.

(2013) [31]

France

Population-based case-control study with 1232 cases of breast cancer and 1317 population controls

Information on shift work obtained from in-person interviews;

Overnight: night shift of 6 consecutive work hours or more spanning the time period 11 pm–5 am

Never

1.0 (ref)

<  4.5 years

1.27 (0.83–1.94)

4.5 years and more

1.40 (0.96–2.04)

Li et al.

(2015) [32]

China

An extension of a series of case-cohort studies of textile industry exposures to dusts, chemicals, and other physical agents in relation to risks of various cancers

Night work was defined as continuous work between 24:00 and 05:00 

Day workers

1.0 (ref)

3 times/month

1.4 (0.8–2.6)

1–14 years

1.2 (0.9–1.6)

15–29 years

1.2 (0.9–1.7)

>  30 years

0.8 (0.5–1.4)

Papantoniou et al.

(2015) [33]

Spain

Population-based case-control study with 1708 breast cancer cases and 1778 population controls from 10 Spanish regions

Lifetime occupational history was assessed by face-to-face interviews

Never night work

1 (ref)

Ever night work

1.18 (0.97, 1.43)

Permanent

1.19 (0.89, 1.60)

Rotating

1.17 (0.91, 1.51)