Creatures of Habit - Why Sleep is Critical

When people think of carcinogens, they might think of UV radiation, processed meat, or BPA.  A lesser-known carcinogen, according to recent research, is a disrupted circadian rhythm.  In other words, not sleeping enough, or sleeping irregularly, can have negative effects for prostate cancer risk.

Research has found a strong positive association between working the night shift and an increased risk of prostate cancer (Flynn-Evans, Mucci, Stevens & Lockley, 2013).  This is probably due to the presence of artificial light in night work. Another study of 305,057 employed American men found an increased risk of prostate cancer among men who slept less than seven hours a night (Gapstur et al., 2014).  Among older people, the association is strong as well.  A study of elderly Icelandic men found that those who had problems sleeping showed signs of increased prostate cancer risk (Sigurdardottir et al., 2014).  These findings support the notion that good, regular sleep lowers the risk of prostate cancer.

In your daily efforts to prevent prostate cancer, it is essential to get a good night’s sleep.  The biggest factor affecting restful sleep is your circadian rhythm, a schedule in your body that governs the release of specific hormones at specific times of the day.  (Circadian comes from the Latin circa and dies, together meaning approximately a day.)  The circadian rhythm, in turn, responds to the level of light in the environment.  At sunrise, for example, your body releases cortisol.  At sunset, it releases melatonin.  It should be no surprise that increased cortisol indicates arousal, and melatonin induces sleepiness.

The problem for modern aspiring sleepers is that our environment causes problems for our circadian rhythms.  Hundreds of years ago, it was difficult to find light after sunset.  The regular ebb and flow of a single, powerful light source made sleep an easy concept for our bodies to understand.  Today, night lights are difficult to avoid, and our bodies have no idea when to fall asleep.  The artificial light of a smart phone, a computer, a street light, or even a desk lamp can trick our naïve bodies into thinking it’s still daytime at 10PM, or worse, time to wake up and start the day.

Artificial light poses an immediate problem for our daily rest as well as a long term, and more serious, problem for our prostate cancer risk.  One solution to this problem is to manage your routine leading up to bedtime to help your body understand what time it is.  Here are some tips.

  1. Getting a good night’s sleep starts as soon as you wake up.  Breakfast serves as a signal to your body that the day has started and that the metabolism must spring back into action.  Another way to kick start your metabolism in the morning is to do some moderate physical exercise.
  2. Limit caffeine intake during the day, and drink no caffeine in the six hours leading up to sleep.
  3. For two hours before the time you would like to fall asleep, minimize artificial light.  Turn off the computer, the iPad, and the Smart Phone.
  4. If your job requires you to sleep during the day, create darkness at bedtime by shutting the blinds or wearing a sleep mask.  Consider investing in a special alarm clock with a light on it that can simulate dawn or dusk.

For more information, check out our previous posts on sleep and melatonin. 

If you’re not a night worker, listen to your body’s daily cycles.  Establish a sleep routine, and stick to it.  If you are a night worker, don’t quit your job, but design your sleep routine and your sleep environment to make room for your circadian rhythm.  Not only will you feel better in general, but you will lower your risk of prostate cancer long term. 



Drake, C., Roehrs, T., Shambroom, J., & Roth, T. (2013). Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med, 9(11), 1195-1200. doi: 10.5664/jcsm.3170

Flynn-Evans, E. E., Mucci, L., Stevens, R. G., & Lockley, S. W. (2013). Shiftwork and prostate-specific antigen in the National Health and Nutrition Examination Survey. J Natl Cancer Inst, 105(17), 1292-1297. doi: 10.1093/jnci/djt169

Gapstur, S. M., Diver, W. R., Stevens, V. L., Carter, B. D., Teras, L. R., & Jacobs, E. J. (2014). Work schedule, sleep duration, insomnia, and risk of fatal prostate cancer. Am J Prev Med, 46(3 Suppl 1), S26-33. doi: 10.1016/j.amepre.2013.10.033        

Sigurdardottir, L. G., Markt, S. C., Rider, J. R., Haneuse, S., Fall, K., Schernhammer, E. S., . . . Mucci, L. A. (2014). Urinary Melatonin Levels, Sleep Disruption, and Risk of Prostate Cancer in Elderly Men. Eur Urol. doi: 10.1016/j.eururo.2014.07.008     

Sigurdardottir, L. G., Valdimarsdottir, U. A., Mucci, L. A., Fall, K., Rider, J. R., Schernhammer, E., . . . Lockley, S. W. (2013). Sleep disruption among older men and risk of prostate cancer. Cancer Epidemiol Biomarkers Prev, 22(5), 872-879. doi: 10.1158/1055-9965.epi-12-1227-t