Should doctors prescribe exercise?

“Although the data vary by different cancer types, there is a consistent trend suggesting that moderate daily exercise has a beneficial effect on preventing certain cancers. If you are a reasonably healthy adult, your should exercise regularly.” 

Let’s look at the relationship of exercise and selected cancers. The American Society of Clinical Oncology (ASCO) has done a nice job of summarizing:

Breast Cancer

While the amount of risk reduction varies among studies (20-80%), most suggest that 30 to 60 minutes of moderate to high-intensity exercise per day lowers breast cancer risk. Women who are physically active throughout their life appear to benefit the most, but those who increase physical activity after menopause also fare better than inactive women.1

Colon Cancer

Research suggests that people who increase their physical activity can lower the chance of developing colon cancer by 30 to 40% relative to sedentary adults.1,2 A decrease in colon cancer risk can be achieved regardless of body mass index (BMI) and people who are most active benefit the most. There is insufficient evidence of a protective effect of physical activity on the risk of rectal cancer (a protective effect was seen in some case-control studies, but not in cohort studies).3

Endometrial, Lung and Ovarian Cancer

A handful of studies have suggested that women who are physically active have a 20-40% reduced risk of endometrial cancer compared to those who don’t exercise.1 Higher levels of physical activity seem to also protect against lung cancer (up to 20% reduction in risk), particularly among men.1Although less consistent, research suggests that physical activity possibly reduces the risk of ovarian and prostate cancer.

What about Other Cancers?

While observational data on the benefits of exercise for prevention of the types of cancers listed above are fairly consistent, evidence of the effects of exercise on prevention of any other type of cancer either is either insufficient or inconsistent.2,4

Prostate Cancer

Prostate cancer is one disease in which the data are not consistent, however prostate cancer is a heterogeneous disease and risk factor associations for total non-aggressive disease are different from aggressive / lethal disease. Most population based studies show similar findings, with little effect of exercise on overall incidence of prostate cancer but lower risk of aggressive prostate cancers for those with the highest levels of VIGOROUS activity (rather than any type of activity). In the Health Professionals Follow-up Study men 65 years or older who engaged in vigorous physical activity, such as running, jogging, biking, swimming or tennis at least three hours per week  had a 67% lower risk of advanced prostate cancer and 74% lower risk of fatal prostate cancer.5

Conflicting data for other malignancies

For example, one recent study found no association between physical activity and risk of developing gastric, rectal, pancreatic, bladder, testicular, kidney and hematological cancers.4 In contrast, a pooled analysis of data from prospective trials with 1.4 million participants found that physical activity was linked to lower risk of 13 cancers: esophageal, lung, kidney, gastric, endometrial, myeloid leukemia, myeloma, colon, head and neck, rectal, bladder, and breast.6Interestingly, leisure-time physical activity was associated with a higher risk of melanoma (presumably due to time spent outdoors) and prostate cancer, although it is not clear from these data whether that association was with nonaggressive or aggressive prostate cancer.

While we wait for confirmation and clarity on the role of exercise in preventing all the 200+ types of cancer – should doctors prescribe exercise? The answer is simple: yes, because evidence of the protective role of exercise is already strong for some of the most common cancers.

References

  1. Lee I, Oguma Y. Physical activity. In: Schottenfeld D, Fraumeni JF, editors. Cancer Epidemiology and Prevention. 3rd ed. New York: Oxford University Press, 2006.
  2. Slattery, ML. Physical activity and colorectal cancer. Sports Medicine 2004; 34(4): 239–252.
  3. Pham NM, et al. Physical activity and colorectal cancer risk: an evaluation based on a systematic review of epidemiologic evidence among the Japanese population. Jpn J Clin Oncol. 2012 Jan;42(1):2-13.
  4. Friedenreich CM, Neilson HK, Lynch BM. Eur J Cancer. State of the epidemiological evidence on physical activity and cancer prevention. 2010 Sep;46(14):2593-604.
  5. Giovannucci E, Liu Y, Leitzmann MF, et al. A prospective study of physical activity and incident and fatal prostate cancer. Arch Intern Med. 2005; 165(9):1005-1010.
  6. Moore SC, Lee IM, Weiderpass E, et al. Association of Leisure-Time Physical Activity With Risk of 26 Types of Cancer in 1.44 Million Adults. JAMA Intern Med. 2016 Jun 1;176(6):816-25.
  7. http://www.asco.org/about-asco/press-center/asco-resources-media/cancer-perspectives/should-cancer-doctors-prescribe?et_cid=38723632&et_rid=463715101&linkid=Read+more

I’m Dr. Michael Hunter. Of course, the disclaimer: Do not begin an exercise program without input from an appropriate medical professional. Many can simply start with a brisk walk for 30 minutes daily, 5 days per week. Have a wonderful day!

Light-emitting e-readers Before Bedtime Adversely Impact Sleep

What You Need to Know: Use of a light-emitting electronic device (LE-eBook) in the hours before bedtime can adversely impact overall health, alertness, and the circadian clock which synchronizes the daily rhythm of sleep to external environmental time cues.

“We found the body’s natural circadian rhythms were interrupted by the short-wavelength enriched light, otherwise known as blue light, from these electronic devices,” said Anne-Marie Chang, PhD, corresponding author. “Participants reading an LE-eBook took longer to fall asleep and had reduced evening sleepiness, reduced melatonin secretion, later timing of their circadian clock and reduced next-morning alertness than when reading a printed book.”

Background: Previous research has shown that blue light suppresses melatonin, impacts the circadian clock and increase alertness, but little was known about the effects of this popular technology on sleep. The use of light emitting devices immediately before bedtime is a concern because of the extremely powerful effect that light has on the body’s natural sleep/wake pattern, and may thereby play a role in perpetuating sleep deficiency.

The Study: During the two-week inpatient study, twelve participants read LE-e-Books on an iPad for four hours before bedtime each night for five consecutive nights. This was repeated with printed books. The order was randomized with some reading the iPad first and others reading the printed book first.

  • IPad readers took longer to fall asleep, were less sleepy in the evening, and spent less time in REM sleep. IPad readers had reduced secretion of melatonin, a hormone which normally rises in the evening and plays a role in inducing sleepiness.
  • IPad readers had a delayed circadian rhythm, indicated by melatonin levels, of more than an hour. Participants who read from the iPad were less sleepy before bedtime, but sleepier and less alert the following morning after eight hours of sleep.

Although iPads were used in this study, BWH researchers also measured other eReaders, laptops, cell phones, LED monitors, and other electronic devices, all emitting blue light.

“In the past 50 years, there has been a decline in average sleep duration and quality,” stated Charles Czeisler, PhD, MD, FRCP, chief, BWH Division of Sleep and Circadian Disorders. “Since more people are choosing electronic devices for reading, communication and entertainment, particularly children and adolescents who already experience significant sleep loss, epidemiological research evaluating the long-term consequences of these devices on health and safety is urgently needed.”

My Take: These findings are important and should be considered, given recent evidence linking chronic suppression of melatonin secretion by nocturnal light exposure with the increased risk of breast cancer, colorectal cancer and prostate cancer. I’m Dr. Michael Hunter, and I no longer use any blue light-emitting devices in the hour before bedtime.

The small print: The material presented herein is informational only, and is not designed to provide specific guidance for an individual. Please check with a valued health care provider with any questions or concerns. As for me, I am a Harvard- , Yale- and UPenn-educated radiation oncologist, and I practice in the Seattle, WA (USA) area. I feel genuinely privileged to be able to share with you. If you enjoyed today’s offering, please consider clicking the follow button at the bottom of this page.

Available now: Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Both can be found at the Apple Ibooks store. Coming Soon for iPad: Understand Breast Cancer in 60 Minutes; Understand Colon Cancer in 60 Minute; Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Thank you.

Journal References

  • Anne-Marie Chang, Daniel Aeschbach, Jeanne F. Duffy, and Charles A. Czeisler. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. PNAS, December 22, 2014 DOI: 10.1073/pnas.1418490112
  • Brigham and Women’s Hospital (Harvard). “Light-emitting e-readers before bedtime can adversely impact sleep.” ScienceDaily. ScienceDaily, 22 December 2014. <www.sciencedaily.com/releases/2014/12/141222131348.htm>.

Breast Cancer & Circadian Rhythm Disruption from Electric Lighting

woman sleeping serenely

What You Need to Know: With industrialization comes electricity to light the night, both within the home and outside of it. A convergence of research in cells, rodents, and humans suggests that the health consequences of circadian disruption may be substantial. Evidence is accumulating to suggest that exposure to light at night may present a risk for breast cancer. It is not unwise to keep your night sleep time as dark as possible.

Background: Breast cancer is the leading cause of cancer death among women worldwide. Risk is highest in economically developed countries, and is rising rapidly in places that have historically had a low risk of the disease. Until the 1980s the researchers believed that this increase might be primarily related to diet. Yet, the evidence linking fat content in the adult diet to breast cancer (and showing decreases with fruit and vegetable consumption) is rather weak. In fact, other than alcohol, overall diet composition has not been strongly associated with breast cancer risk. Body mass has been linked, however. In fact, less than half of the risk in high-risk societies can be attributed to known risk factors. While recent evidence shows that physical activity can lower risk, a decrease in such activity is not likely accountable for the additional risk found in industrialized countries. So, besides obesity, less physical activity, and the use of hormones, could increased exposure to light during the dark hours (which can disrupt the “sleep hormone” melatonin be a culprit?

breast cancer tumor

The Evidence Linking Circadian Rhythm Disruption and Breast Cancer: The first suggestion that light at night might explain a portion of the breast cancer pandemic was made in 1987. The hypothesis was based on the idea that exposure to light at night would result in melatonin suppression, which in turn would increase breast cancer risk as described in the previous section. Since 1987, a series of predictions of this theory have been tested. Let’s turn to some of the evidence:

  • Shift work: Women who work nights (shift work) are at higher risk of breast cancer. The International Agency for Research on Cancer concluded that “shift work that includes circadian rhythm disruption is probably carcinogenic to humans.” The American Medical Association then broadened the topic in 2012 on the health habits of light at night in general. While subsequent studies have had mixed results, a meta-analysis (including a study of high-quality studies) linked night work to an increased risk (by a factor of 1.4).
  • Blind women: Four studies have suggested that blind women may be at a lower risk of breast cancer than sighted women.
  • Ecological analyses: Kloog analyzed cancers (lung, colon, larynx, and liver) in 164 countries. Breast cancer was significantly associated with nighttime illumination, and it was estimated that the risk was increased by a factor of 1.3 to 1.5, compared with the lowest lighted countries. The investigators controlled for fertility rate, per capita income, percent of urban population, and electricity consumption.
  • Genetics (circadian gene polymorphisms): Researchers first linked a circadian gene polymorphism to breast cancer risk in 2005.
  • Differences in methylation of circadian genes have been found when comparing day shift and night shift workers, offering a possible mechanism for an increased risk among night workers.

My Take: It is clear that electric lighting, including indoor evening light levels, has strong effects on our circadian rhythms. Recent studies show that the lighting used in at the typical home (in the industrialized world) is enough to delay melatonin onset and blunt its night peak. So here is what I would like you to do:

  • Limit your night exposure to light, whether from computer screens (the emitted light in the blue spectrum changes melatonin levels) or to night lights.
  • Sleep in a dark room, if possible (no light from the clock next to the bed, or seeping into your room from street lights, for example). Nocturnal light exposure and circadian disruption may be particularly important for children, and even exposure to light as a pregnant woman may affect fetal exposure to hormone levels in utero.

So many questions remain: Might circadian rhythm disruption affect your response to chemotherapy? Could it affect the natural history of breast cancer and affect the risk or pace of progression? Can we control our lighting in a more sophisticated fashion that might not be so disruptive? I’m Dr. Michael Hunter, and I thank you for reading this very long blog.

The small print: The material presented herein is informational only, and is not designed to provide specific guidance for an individual. Please check with a valued health care provider with any questions or concerns. As for me, I am a Harvard- , Yale- and UPenn-educated radiation oncologist, and I practice in the Seattle, WA (USA) area. I feel genuinely privileged to be able to share with you. If you enjoyed today’s offering, please consider clicking the follow button at the bottom of this page.

Available now: Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Both can be found at the Apple Ibooks store. Coming Soon for iPad: Understand Breast Cancer in 60 Minutes; Understand Colon Cancer in 60 Minute; Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Thank you.

Reference: RG Stevens et al. Breast Cnacer and Cricadian Disruption from Electric Lighting in the Modern World. CA Cancer J Clin 2014;64: 207-218.

 

Want To Stay Young? Start Moving.

women walking exercise

A new study finds that exercise among older adults helps ward off depressiondementia and other health problems, such as heart diseasecancer and diabetes. Exercise increased the odds of healthy aging as much as sevenfold, the researchers found. And apparently it’s never too late to start: Even adults who don’t begin exercising until they’re older could increase their odds of healthy aging threefold, the researchers said.

“In a growing elderly population, it is important to encourage healthy aging. Physical activity is effective in maintaining health in old age,” said lead researcher Mark Hamer, from the department of epidemiology and public health at University College London, in England.

For the study, Hamer and his colleagues collected data on nearly 3,500 people with an average age of 64 who took part in the English Longitudinal Study of Aging.

As part of the study, the participants reported their level of physical activity every two years between 2002-’03 and 2010-’11. The researchers categorized the participants by how much exercise they did each week. There were those who were inactive, those who did moderate exercise and those who exercised vigorously.

People who partook in moderate or vigorous physical activity at least once a week were three to four times more likely to be healthy agers, compared with those who remained inactive, the researchers found. Moreover, people who were active at the start of the study were seven times more likely to be healthy agers than people who were inactive and remained so, the researchers found.

My Take: Want to stay healthy? Get moving. I’m Dr. Michael Hunter.

The small print: The material presented herein is informational only, and is not designed to provide specific guidance for an individual. Please check with a valued health care provider with any questions or concerns. As for me, I am a Harvard- , Yale- and UPenn-educated radiation oncologist, and I practice in the Seattle, WA (USA) area. I feel genuinely privileged to be able to share with you. If you enjoyed today’s offering, please consider clicking the follow button at the bottom of this page.

Available now: Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Both can be found at the Apple Ibooks store. Coming Soon for iPad:  Understand Breast Cancer in 60 Minutes; Understand Colon Cancer in 60 Minute; Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Thank you.

Reference: The report was published online Nov. 25 in the British Journal of Sports Medicine.

Depression Does Not Increase Cancer Risk

depression young woman depressed sad lonely

Does psychological depression increase your risk of getting cancer? We have long-suspected a link, but there is no good study to either confirm or reject this hypothesis. That is, until now.

The Study: The INSERM’s Mixed Research Unit 1018 “Epidemiology and Population Health Research Centre,” AP-HP, University of Versailles Saint-Quentin monitored 14203 people between 1994 and 2009, including 1119 who developed cancer. All of the absences from work for depression (certified by doctors) were recorded as well as many questionnaires measuring depressive moods. Five major types of cancer were monitored, including prostate, breast, colon, cancer associated with smoking, and cancer of the lymph nodes or blood (leukemias). THe mean (average) follow-up was 15.2 years.

The Results: Depression does not appear to increase the risk of getting cancer. Of course, a cancer diagnosis can cause symptoms of depression, so let your care team know if you feel down!

The small print: The material presented herein is informational only, and is not designed to provide specific guidance for an individual. Please check with a valued health care provider with any questions or concerns. As for me, I am a Harvard- , Yale- and UPenn-educated radiation oncologist, and I practice in the Seattle, WA (USA) area. I feel genuinely privileged to be able to share with you. If you enjoyed today’s offering, please consider clicking the follow button at the bottom of this page.

Available now: Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Both can be found at the Apple Ibooks store. Coming Soon for iPad:  Understand Breast Cancer in 60 Minutes; Understand Colon Cancer in 60 Minutes. Available now: Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Thank you.

Reference: C. Lemognem S,N, Consoli, M. Melchior et al. Depression and the Risk of Cancer: A 15-year Follow-up Study of the GAZEL Cohort. Am J of Epidemiology 2013.