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Effects of Physical Inactivity on Health: Part 2 - Heart Disease, Cancer, and Stroke

cancer heart disease physical inactivity stroke Aug 22, 2022

Introduction

How often do you tell yourself “you need to workout”, but then talk yourself out of it? “I just need a little motivation”, one might say, to go on a walk or start an exercise regimen. I think most people inherently know that exercising is good for their health, but what does that actually mean, specifically? What are the health conditions and ailments physical activity protects you from? What are the implications of not being physically active? Why aren’t the answers to these questions common knowledge? Once you’ve established a why for your actions it is easier to go above and beyond to uphold your goals. The purpose of this article is to outline the role physical inactivity plays in the manifestation of major chronic diseases. We’re going to talk specifically about diseases that are within the top 10 causes of death in the US, and how physical activity influences the expression of these diseases. Here are the top 10 causes of death in the US in order: (1)
  1. Heart disease

  2. Cancer

  3. Accidents (unintentional injuries)

  4. Chronic lower respiratory diseases

  5. Stroke (cerebrovascular diseases)

  6. Alzheimer’s disease

  7. Diabetes

  8. Nephritis, nephrotic syndrome, and nephrosis

  9. Influenza and pneumonia

  10. Intentional self-harm (suicide)

The World Health Organization (WHO) defined chronic disease as “diseases of long duration and generally slow progressions”. (2) Another article described chronic disease as “generally characterized by uncertain etiology, multiple risk factors, a long latency period, a prolonged course of illness, non-contagious origin, functional impairment or disability, and incurability.” (3) We’re going to break down heart disease, cancer, and stroke independently and point out the role physical inactivity played in its manifestation, as well as, the risk reduction for engaging in physical activity.
Coronary Heart Disease (Heart Disease)
Coronary heart disease is defined by atherosclerosis (plaquing) in the heart arterial supply, limiting blood flow and therefore oxygen to the heart muscles, resulting in cell death. Cardiorespiratory Fitness (CRF) is described as the maximum amount of oxygen your body can take in and absorb through the tissues to handle aerobic activities (walking, running, swimming, cycling). METs, which are metabolic equivalents, tells us how many calories are being burned during activities and is directly related to the maximum amount of oxygen we can consume (CRF). In a study of CRF, over 19,000 men were tested for their CRF, 15,400 of those men were considered healthy and 3,700 men were diagnosed with metabolic syndrome. Based on their level of CRF, they were divided into 3 groups: High, medium, and low CRF. When they compared the groups together, the middle and lower groups had a 2.08 and 3.48 times greater risk of death of cardiovascular disease, compared to the upper group. (4) Another study that took 44 year old men examined their MET’s and rate of mortality over an 11 year period. They found that for every 1-MET loss in CRF in 14,345 men equated to about a 19% increase of death due to cardiovascular disease. (5) Those within the study who had low CRF had a 27% greater risk of cardiovascular disease death, as opposed to a 39% decreased risk in cardiovascular disease related death in those who had a high CRF. (5)
Cancer
There are specific cancers that have been studied extensively, breast and colon cancer. One meta-analysis (highest level of evidence) regarding breast cancer examined 73 studies and found that there is about a 25% risk reduction for those who are more physically active. (6) It has been stated by the same author in another study that the development of breast cancer is a multifactorial equation, but is likely interrelated with physical activity. (7)
As for colon cancer, a meta-analysis determined that there is about a 24% increased risk of developing colon cancer for those who are the least active; when compared to those who engage in more physical activity. (8) That same study went on to describe the mechanism for those who were least active, such as, insulin resistant, hyperinsulinemia, pro-inflammatory pathways, immune dysfunction, visceral obesity, increased stool transit time (increasing exposure of the carcinogens to the colon) and lower vitamin D levels. (8)
Physical inactivity has been linked to other organ specific cancers, however, the level of evidence is variable. One report looked at over 1.44 million adults with an average age of 59 and their leisure-time physical activity (activity above 3 METs and at their discretion). Through this group they compared 26 different types of cancer with the 186,932 cases of cancer discovered (no cancer was detected at baseline). When they compared the 90th percentile (highest leisure-time physical activity) to the 10th percentile (lowest leisure-time physical activity) there was greater than 20% reduction in esophageal adenocarcinoma, endometrial cancer, gastric cardia, kidney, liver, lung, myeloid leukemia. (9)
Stroke
A stroke is caused by the same core mechanisms that a myocardial infarction (heart attack) is caused by, that is the fact that tissue is not acquiring oxygen; usually due to an obstruction in the main arterial supply or a rupture of an artery. Risk factors identified for strokes are high blood pressure, high cholesterol and lipids, and diabetes. High levels of CRF (oxygen absorption rate) reduces the prevalence of high blood pressure, hyperlipidemia, inflammation, insulin resistance, metabolic syndrome, and type II diabetes (10). In fact, for every 1 MET gained during CRF resulted in a 19% reduced incident risk of hypertension (high blood pressure) amongst women over a 5 year period. As far as stroke itself, a meta-analysis compared a low physical activity group to a moderate and high physical activity group. They found that the moderate physical activity group had an 11% lower risk of stroke and the high physical activity group had a 19% reduced risk of stroke. (11)
Figure 1: Conceptual framework for the benefits of physical activity (12)
Conclusion
I believe we’ve demonized physical activity in society. We’ve disguised physical activity as only being a strategy for losing weight. Weight is controlled in the kitchen, exercising supplements the weight loss process. Physical activity represents increasing cardiorespiratory fitness capacity, which unlocks the benefits provided by moving your body. We have to shift our aim away from weight loss and set our target as cardiorespiratory fitness and strength training. CRF provides the benefits of reducing our risk of all cause mortality, heart disease, diabetes, hypertension, and cancer. Strength training increases our bone density and muscle strength, reducing our frailty. Both CRF and strength training reduce anxiety and depression, supporting our psychological well being. The bottom line of the overwhelming evidence is if you could get the benefits of physical activity in a pill form, everybody would be taking it.

 

References:

  1. “FASTSTATS - Leading Causes of Death.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 19 Oct. 2021, https://www.cdc.gov/nchs/fastats/leading-causes-of-death.htm.
  2. Global Health Risks Report - Who. https://www.who.int/healthinfo/global_burden_disease/GlobalHealthRisks_report_full.pdf.
  3. Goodman, Richard A., et al. “Defining and Measuring Chronic Conditions: Imperatives for Research, Policy, Program, and Practice.” Preventing Chronic Disease, vol. 10, 2013, https://doi.org/10.5888/pcd10.120239.
  4. Katzmarzyk, Peter T., et al. “Cardiorespiratory Fitness Attenuates the Effects of the Metabolic Syndrome on All-Cause and Cardiovascular Disease Mortality in Men.” Archives of Internal Medicine, vol. 164, no. 10, 2004, p. 1092., https://doi.org/10.1001/archinte.164.10.1092.
  5. Lee, Duck-chul, et al. “Long-Term Effects of Changes in Cardiorespiratory Fitness and Body Mass Index on All-Cause and Cardiovascular Disease Mortality in Men.” Circulation, vol. 124, no. 23, 2011, pp. 2483–2490., https://doi.org/10.1161/circulationaha.111.038422.
  6. Friedenreich, Christine M. “The Role of Physical Activity in Breast Cancer Etiology.” Seminars in Oncology, vol. 37, no. 3, 2010, pp. 297–302., https://doi.org/10.1053/j.seminoncol.2010.05.008.
  7. Friedenreich, Christine M. “Physical Activity and Breast Cancer: Review of the Epidemiologic Evidence and Biologic Mechanisms.” Clinical Cancer Prevention, 2010, pp. 125–139., https://doi.org/10.1007/978-3-642-10858-7_11.
  8. Wolin, K Y, et al. “Physical Activity and Colon Cancer Prevention: A Meta-Analysis.” British Journal of Cancer, vol. 100, no. 4, 2009, pp. 611–616., https://doi.org/10.1038/sj.bjc.6604917.
  9. Moore SC, Lee IM, Weiderpass E, Campbell PT, Sampson JN, Kitahara CM, Keadle SK, Arem H, Berrington de Gonzalez A, Hartge P, Adami HO, Blair CK, Borch KB, Boyd E, Check DP, Fournier A, Freedman ND, Gunter M, Johannson M, Khaw KT, Linet MS, Orsini N, Park Y, Riboli E, Robien K, Schairer C, Sesso H, Spriggs M, Van Dusen R, Wolk A, Matthews CE, Patel AV. Association of leisure-time physical activity with risk of 26 types of cancer in 1.44 million adults. JAMA Intern Med 176: 816–825, 2016. doi:10.1001/jamaintermed.2016.1548
  10. Bauman, Adrian, et al. “Updating the Evidence for Physical Activity: Summative Reviews of the Epidemiological Evidence, Prevalence, and Interventions to Promote ‘Active Aging.’” The Gerontologist, vol. 56, no. Suppl 2, 2016, https://doi.org/10.1093/geront/gnw031.
  11. Barlow, Carolyn E., et al. “Cardiorespiratory Fitness Is an Independent Predictor of Hypertension Incidence among Initially Normotensive Healthy Women.” American Journal of Epidemiology, vol. 163, no. 2, 2005, pp. 142–150., https://doi.org/10.1093/aje/kwj019.
  12. United States Department of Health and Human Services. 2008 Physical Activity Guidelines for Americans: Be Active, Healthy, and Happy! Washington, DC: U.S. Dept. of Health and Human Services, 2008, p. Ix.
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