Table 1.

Main characteristics and risk estimates of the 16 epidemiologic studies on circadian disruption or sleep loss and prostate cancer risk

Study; CountryStudy design, population (participation rate) and time period under observationSource of information for exposure (i.e., circadian disruption or sleep loss)Adjusted covariatesNumber of prostate cancer casesRisk estimate (95% CI)
Light at night
Kloog and colleagues (2009); United StatesEcologic study of 164 different countries; 2002.Per capita light at night obtained from the U.S. Defense Meteorologic Satellite Program. Per capita GDPa, percent urban population, and per capita electricity consumption obtained from the ESRI ArcCI Sdatabase and the CIAb World Fact Book, 1998–1999.Income level and percent urban population.
Sleep duration
Kakizaki and colleagues (2008); JapanProspective cohort study of 22,320 men from the general population of Miyagi (94%); 1995–2001.Sleep duration obtained from questionnaires and categorized into 3 groups: 6 ≤,7–8, ≥9 hours per day. Those who slept less than 4 h or more than 12 h were excluded.Age, marital status, education, job status, history of disease, family history of cancer, body mass index, cigarette smoking, alcohol consumption, and walking status.21 (≤6 h)19 (≥9 h)HR 1.38 (0.77–2.48)HR 0.36 (0.18–0.72)
Shift work
Kubo and colleagues (2011); JapanRetrospective cohort study of 4,995 male workers; 1981–2009.Industry-based health-care database of a Japanese corporation that had recorded the results of annual health check-ups and the work schedule of every employee since 1981. Exposue classified as having worked on continuous counter-clockwise 3-shift system for >80% of their career.Age, body mass index, alcohol intake, smoking, exercise and marriage status.17OR 1.56 (0.51–4.80)
Schwartzbaum and colleagues (2007); SwedenHistorical population-based occupational cohort study of 2,102,126 employed men (84% in ULFc); 1971–1989.Cohort member's occupation obtained from the 1960 and 1970 censuses. Occupation classified as shift work if at least 40% were engaged in rotating shifts or working any hour 0100–0400 at least once a week during 1977–1981 according to the ULFc. Occupations with <30% of people engaged in shift work used as comparison.Age, socioeconomic status, occupational position, county of residence, marital status, and urbanization.1,319SIRd 1.04 (0.99–1.10)
Kubo and colleagues (2006); JapanProspective population-based cohort study of 14,052 employed men (83%); 1991–1997.The longest held work schedule obtained from questionnaires of the JACCe Study in 1988–1990, grouped into daytime, fixed night, or rotating shift work.Age, study area and family history7 (rotating)3 (fixed)HR 3.0 (1.2–7.7)HR 2.3 (0.6–9.2)
Conlon and colleagues (2007); CanadaCase–control study of 760 cases and 1,632 controls; 1995–1998.Ever having worked rotating full-time shift work for 1 year or more. Usual work time obtained from questionnaires. Categories of all subjects and age 23–29 years when first working full-time rotating shift work (other categories of exposure omitted.)Age and family history of prostate cancer.760 (all subjects)107 (young when started shift work)OR 1.19 (1.00–1.42)OR 1.38 (1.05–1.80)
Proxy for shift work
Pukkala and colleagues (2009); Nordic countriesRetrospective cohort study of 14.9 million persons in the 5 Nordic countries.Study base consisted of persons participating in any computerized population census 1960–1990 grouped into 54 occupational categories: we present data for public safety workers and waiters. Followed until December 31st 2005 at latest.Gender, age (5-year categories) and calendar (5-year periods).4,893 (public safety workers)490 (waiters)SIR 1.11 (1.08–1.14)SIR 1.10 (1.01–1.20)
Bates (2007); CaliforniaCase–Control study of 3,659 firefighters diagnosed with cancer.Firefighters aged 21–80 and diagnosed with prostate cancer during 1988–2003. Subjects with all other cancers, except outcome measure and cancers that were associated with firefighter occupation, used as a comparison group.Age (5-year categories), year of diagnosis (4-year categories), ethnicity, socioeconomic status.1,144OR 1.22 (1.12–1.33)
Buja and colleagues (2005); ItalyMeta-analysis of 9 studies of which 5 include prostate cancer incidence; 1943–1996.Pilots (3 studies) and male flight attendants (not included).104SIR 1.47 (1.06–2.05)
Pukkala and colleagues (2002); Nordic countriesRetrospective cohort study of 10,032 male airline pilots; 1943–1997.Male pilots with number of block hours. Aircrafts classified into low altitude, intermediate distance, and long distance categories; total and age >60 years with more than 10,000 block hours.Calendar periods and broad age categories.64 (total)SIR 1.21 (0.93–1.54)
8 (>10,000 h)SIR 3.88 (1.26–11.9)
Ballard and colleagues (2000); ItalyMeta-analysis of 6 studies of which 4 include prostate cancer; 1986–1998.Civilian pilots (2 mortality studies and 2 incidence studies) and female flight attendants.Correction factor of 1.1 for socioeconomic status.23SMR 1.11 (0.70–1.75)
40SIR 1.65 (1.19–2.29)
Irvine and colleagues (1999); Britain6,209 male pilots and 1,153 male flight engineers employed for at least 1 year; 1950–1992.Male British Airways flight deck crew compared with the general population of England and Wales.15SMR 1.11 (0.62–1.83)
Nicholas and colleagues (1998); United StatesCase–control study of 1,538 diseased pilots and navigators; 1984–1991.Death certificates of commercial pilots and navigators. Expected numbers based on the 24-state data for all occupations.Race, gender, age, and region.38MOR 1.46 (1.06–2.03)
Krstev and colleagues (1998); United StatesCase–control study of 60,878 men diagnosed with prostate cancer, by occupation; 1984–1993.Death certificate-based occupational mortality data, with prostate cancer as an underlying cause of death. Comparison group subjects who died of all other causes except cancer.5-year age groups and race.37 (pilots and navigators)140 (firefighters)20 (police and detectives)MOR 1.4 (1.0–2.0)MOR 1.2 (1.0–1.4)MOR 1.6 (1.0–2.5)
Band and colleagues (1996); CanadaRetrospective cohort study of 2,680 pilots (97.8%); 1950–1992.All male pilots employed for at least one year since 1950.5-year age groups and 5-year calendar periods.347SIR 1.87 (1.38–2.49)SMR 1.52 (0.71–2.85)
Band and colleagues (1990); CanadaRetrospective cohort study of 891 pilots (97.6%); 1950–1988.All male pilots employed since 1950.5-year age groups and 5-year calendar periods.6SIR 1.54 (0.70–3.00)f
  • aGDP, gross domestic products; bCIA, Central Intelligence Agency; cULF, annual Survey of Living Condition conducted by Statistics Sweden; dSIR, standardized incidence ratio; eJACC, Japan Collaborative Cohort, f90% CI.