The earth completes a full rotation on its axis every 24 hours. For the majority of creatures – including humans – who do not live near either the north or south pole, about half of the time it’s day, and the other half is night. With relatively few fluctuations, this daily division of daylight and darkness sets up a regular internal pattern called the circadian rhythm (circa = about, diem = day). Almost all living beings, including plants, animals, fungi and even certain bacteria, have an internal circadian rhythm. In humans, the “master clock” is a small portion of the hypothalamus that “that controls biochemical, physiological and behavioral rhythms, entrained by light and other external signals.”[i] The circadian rhythm determines our eating and sleeping patterns. For example, a typical rhythm includes being most sleepy between 1-3 pm, and 2-4 am. However, people who get insufficient sleep at night tend to have a greater degree of drowsiness in the afternoon than those who enjoyed a full 7-8 hours of sleep the night before.
Almost all biological activities are influenced by this cycle. Our bodies have “clock” genes and proteins that regulate an amazing range of processes:
… the ability to fall asleep or to snap out of sleep into wakefulness, body temperature, blood pressure, hormone biosynthesis, digestive secretion, and immune responses…. Individual normal cells and even cancer cells keep circadian time by expressing similar clock genes.[ii]
Circadian rhythms of various functions are measurable. For instance, testosterone levels are higher at certain times of the day. When a person has the flu, the ebb and flow of fever is subject to circadian rhythm. One person may have a slightly different rhythm than another, but essentially each person’s rhythm is responding to changes in natural light.
Circadian rhythms are not foolproof. The appearance and disappearance of daylight normally keeps circadian rhythms flowing smoothly and on time. However, research shows that disruption is linked with tumor development and progression. The most common disruption occurs for people whose normal rhythm is in sync with nature’s day/night cycle, but their internal clock is deregulated by the demands of jobs, travel, school or other ongoing conditions. People whose work keeps them up at odd hours, or for long stretches, suffer from a condition called “shift work sleep disorder.” And any traveler who has ever experience jet lag knows how disorienting it can be, and how hard to get back to normal.
Published data actually suggests a correlation between higher rates of prostate cancer, including aggressive disease, among shift workers and airline pilots. The genes that regulate normal cells and keep tumors from starting – or keep them in check if a cell mutates into a cancer cell – become dysfunctional when circadian disruption occurs. In a loose sense, without the orderliness of the rhythm, it’s as if the master clock fails to manage things and chaos results. “Results from a population-based case-control study provide evidence for an association of genetic variations in circadian genes with prostate tumorigenesis [the beginning of a tumor].”[iii]
For millions of men and women, circadian disruption is a fact of life. Gone are the pre-Industrial Revolution days when farmers rose before dawn and were in bed by nightfall, factories shut down at 5 o’clock, and most people went to bed soon after dark rather than use precious lamp oil. We live in a 24-hour-a-day world, thanks to brightly shining electric lights and global production demands. If you live in Des Moines and have to be on a conference call with a colleague in Delhi, which one of you will be up in the middle of the night?
Although some disruption is inevitable, it’s in the best interest of your prostate to honor the daily round of light and dark. Read my blog at https://sperlingprostatecenter.com/poor-sleep-prostate-cancer-risk/ to learn about the importance of a good night’s sleep. Remember, too, that when our circadian rhythm is out of whack, we are more prone to the effects of stress, and we create more stress as well due to poor judgment and increased clumsiness. In other words, preserving a normal circadian rhythm is an investment in your total well-being in addition to your prostate health.
As one wise person recognized, it’s a challenge to preserve the precious commodity: “I try to manage my day by my circadian rhythms because the creativity is such an elusive thing, and I could easily just stomp over it doing my administrative stuff.”[iv] But it’s well worth being aware of, and doing your best to honor it.
[i] Savvidis C, Koutsilieris M. Circadian rhythm disruption in cancer biology. Mol Med. 2012;18(1):1249-60.
[ii] Ibid.
[iii] Ibid.
[iv] https://www.brainyquote.com/search_results?q=circadian%20rhythm
About Dr. Dan Sperling
Dan Sperling, MD, DABR, is a board certified radiologist who is globally recognized as a leader in multiparametric MRI for the detection and diagnosis of a range of disease conditions. As Medical Director of the Sperling Prostate Center, Sperling Medical Group and Sperling Neurosurgery Associates, he and his team are on the leading edge of significant change in medical practice. He is the co-author of the new patient book Redefining Prostate Cancer, and is a contributing author on over 25 published studies. For more information, contact the Sperling Prostate Center.
