Working at night increases the risk of prostate cancer

People who work for at least a year during the night have a higher risk (about 15%) for prostate cancer compared with people who have never worked at night. This risk increases the longer the duration of exposure, leading to increased risk to about 40% if the person has worked over 28 years in night shifts. The increased risk of prostate cancer associated with night work is also higher (up to 40%) for the most aggressive tumors with poor prognosis.

CREAL researchers, an ISGlobal allied center, focused on the study of chronotype, a concept related to circadian rhythms and adaptation to night work. They found that the risk is greater in workers with an evening chronotype (although they prefer to work night than morning), but the risk also increases for morning chronotypes if the duration of night work increases.

Specifically, 1,095 prostate cancer cases and 1,388 controls randomized population were included. Detailed information on the night shift (permanent vs rotary, schedules, duration, frequency) through occupationl history, but also additional information on sociodemographic and lifestyle, was collected. 20% of Spanish workers had ever worked night shift. All cases and controls come from the MCC-Spain (http://mccspain.org), a multicase control population-based study in frequent tumors in Spain, which includes 23 hospitals in 12 regions and evaluates 5 cancers (breast, colorectal, prostate, stomach and chronic lymphocytic leukemia).

The International Agency for Research on Cancer (IARC) in 2007 classified night work as a probable carcinogen for humans (group 2A) based on scientific studies conducted to date mainly on the risk of breast cancer. Now this study adds the risk for prostate cancer in men and suggests a possible association with tumors with poorer survival.

Reference: Papantoniou K, Castaño-Vinyals G, Espinosa A, Aragonés N, Pérez-Gómez B, Burgos J, Gómez-Acebo I, Llorca J, Peiró R, Jiménez-Monleón JJ, Arredondo F, Tardón A, Pollán M, Kogevinas M. Night shift work, chronotype and prostate cancer risk in the MCC-Spain case-control study.. Int J Cancer 2014: (in press).