Written by Chrystal Moulton, Staff Writer. This study has determined that sleep disorders and sleep disruption resulted in a higher risk of prostate cancer.

In order to investigate the possible relationship between sleep problems and prostate cancer occurrence, researchers recruited 2,102 men of Iceland not previously diagnosed with prostate cancer. These men were arranged into categories of sleep disturbance based on a questionnaire taken at the onset of the study. Basic background, health, and lifestyle information was also collected at enrollment. Researchers followed each individual participant from the time of recruitment (2002-2006) to the end of the trial in December 31, 2009. Information on the occurrence of prostate cancer and all-cause mortality were obtained through the nationwide Icelandic Cancer Registry. Each participant, being a citizen of Iceland, has a unique number (obtained at enrollment) that allows researchers to seek information needed for this study from this registry. Advanced prostate cancer was defined in this system as T3 when the cancer spread through prostatic structures, T4 when prostate cancer invaded nearby structures, and N1/M1 when cancer spread to lymph nodes. Participants who died from prostate cancer were also categorized as advanced prostate cancer.

Average age and BMI of the participants were 76 years old and 26.9 m/kg2, respectively. At the end of this trial, 135 of 2,102 men developed prostate cancer. Of the 135 men diagnosed with prostate cancer, the Icelandic Registry provided disease stage information on 92 men of whom 16 had advanced prostate cancer. Also, 10 of the 135 men diagnosed with prostate cancer died. Overall, researchers found that problems getting to sleep and staying asleep were associated with an increased risk of prostate cancer (Hazard Ratio [HR] = 1.6 and 2.1 respectively, 95% confidence interval). Association remained even after adjusting for confounding factors including family history, prevalence of doctor visits, education, BMI, diabetes, and benign prostatic disease. Advanced prostate cancer was strongly associated with all types of sleep problems when compared to men without sleep problems (HR= 3.2, 95% confidence interval). In order to assess a potential bias in the information where undiagnosed prostate may be causing the sleep disturbances, the researchers excluded men with potential symptoms of nocturia (waking up during the night). However, association between sleep disturbance and prostate cancer remained with an age-adjusted HR of 2.2 for overall prostate cancer and 3.3 for advanced prostate cancer (95% confidence interval).

In all, researchers found that men with sleep disruption had an increased risk of prostate cancer when compared with men with sleep problems (1). Researchers mentioned that even though their sample size was large, the number of cases used in the assessment for advanced prostate cancer and overall cancer was 26 and 135, respectively. It is entirely possible that other underlying factors may play a role in how sleep disruption affects development of prostate cancer and therefore further research could shed light on this relationship.

Interestingly, it has been determined that melatonin, a naturally occurring hormone that regulates sleep cycle has been found to cause death of prostate cancer cells. In a cell study, it was found that melatonin was able to alter the cellular division of prostate cancer cells by inducing the cells to stay in the growth phase, arrest part of cell cycle (2). The use of melatonin to induce cancer cell death should be further investigated in humans; however it seems likely that melatonin will lower the risk of prostate cancer since its use has been widely used to regulate sleep.

Source: Sigurdardottir, Lara G., et al. “Sleep disruption among older men and risk of prostate cancer.” Cancer Epidemiology and Prevention Biomarkers 22.5 (2013): 872-879.

©2013 American Association for Cancer Research.

Posted July 23, 2013.

References:

  1. Sleep disruption among older men and risk of prostate cancer. Sigurdardottir LG, Valdimarsdottir UA, Mucci LA, et al. Cancer Epidemiol Biomarkers Prev. 2013 May;22(5):872-9. doi: 10.1158/1055-9965.
  2. Kim, Chi Hyun, and Yeong-Min Yoo. “Melatonin induces apoptotic cell death via p53 in LNCaP cells.” The Korean Journal of Physiology & Pharmacology 14.6 (2010): 365-369.