People who walked at least 8,000 steps per day just one or two days a week had a 15 percent lower death rate over the next 10 years, when compared to people who walked less than that (JAMA Netw Open, Mar 29, 2023;6(3):e235184). People who had 3-7 days with 8,000 steps or more had an additional reduction in death rate. This suggests that moving around helps to prolong your life, even if you don’t have an organized exercise program. People who have jobs that require sitting all day can still benefit from being active on weekends. You cover about four miles when you take 8,000 steps.
This study included 3,101 people, average age 50 years, who registered their step counts by wearing wrist accelerometers for seven consecutive days. About 63 percent of those studied took 8,000 steps per day or more at least three days per week, and 17.2 percent more reached 8,000 steps 1-2 days per week. Over the 10-year study period, 14.2 percent of those in the study died and 5.3 percent died from heart disease.
Other studies have shown that increasing the number of steps people take each day:
• decreased dementia risk (JAMA Neurol, 2022;79(10):1059-1063)
• decreased death rate in older people (JAMA, 2006;296(2):171-179)
• decreased death rate in older women, by increasing either the number of steps or the walking speed (JAMA Intern Med, 2019;179(8):1105-1112)
• decreased death rate from heart attacks and cancer just by exercising only on weekends (JAMA Intern Med, 2017;177(3):335-342; Am J Epidemiol, 2004;160(7):636-641; Med Sci Sports Exerc, 2019;51(1):35-40; JAMA Intern Med, 2022;182(8):840-848).
Death from “Natural Causes” Usually Means Death from Inactivity
When you read about people dying of “natural causes,” it usually means that they died of heart failure because they spent too much time lying in bed. When you become inactive, you lose your skeletal muscles at an alarming rate, and losing skeletal muscle causes loss of heart muscle until your heart can become too weak to pump blood to your brain and you die. In 1914, Dr. Ernest Starling described what is today known as Starling’s Law, that strengthening skeletal muscles strengthens heart muscle and not the other way around (Circulation, 2002;106(23):2986-2992). When you contract your skeletal muscles, they squeeze the veins near them to pump extra blood back to your heart. The extra blood flowing back to your heart fills up your heart, which stretches your heart muscle, causing the heart muscle to contract with greater force and pump more blood back to your body. This explains why your heart beats faster and harder to pump more blood when you exercise. The harder your heart muscle has to contract regularly in an exercise program, the greater the gain in heart muscle strength.
• The larger your skeletal muscles, the stronger your heart and the lower your chance of suffering heart attacks and heart disease (J Epidem & Comm Health, Nov 11, 2019).
• The less you exercise, the weaker your heart and the more likely you are to become diabetic (Diabetes Care, 2002; 25:1612–1618).
• The larger your muscles, the less likely you are to die of heart diseases (Am J of Cardiology, Apr 15, 2016;117(8):1355-1360).
• A study of almost a million adults with no history of heart disease followed for 10 years found that those who did not exercise were at 65 percent increased risk for strokes and heart attacks, the same rate as that found for smoking (Euro J of Prev Cardiology, Feb 10, 2020).
• A study of 900 heart failure patients found that those who did not exercise were twice as likely to die within three years (Am J Cardiol, 2016 Apr 1; 117(7): 1135–1143).
• A study of 51,451 people followed for 12.5 years found a strong association between exercise and decreased risk for heart failure (J Amer Col of Cardiol, Mar 2017;69(9)).
• A study of 378 older adults showed that the smaller the muscles in their arms, legs and trunk, the smaller and weaker the upper and lower chambers of their hearts (J Am Geriatr Soc, Dec 2019;67:2568-2573).
• Low skeletal muscle size predicted death in people who had chronic heart failure (Cardiology, March 25, 2019).
Loss of Muscle with Aging is Common
Between 25 and 50 percent of North Americans over the age of 65 suffer from severe loss of skeletal muscle (sarcopenia) that is significant enough to limit their daily activities (J Am Geriatr Soc, 2004;52:80–85). A regular exercise program is the best way to slow down this loss of strength and coordination, but even if you exercise regularly, you will still lose muscle as you age (Aging Male, September-December 2005). After age 40, people lose more than eight percent of their muscle size per decade and by age 70, the rate of muscle loss nearly doubles to 15 percent per decade, markedly increasing risk for disability and disease (Am J Epidemiol, 1998;147(8):755–763; Nutr Rev, May 2003;61(5 Pt 1):157-67).
The people who lose the most skeletal muscle are usually the ones who die earliest. They are also most at risk for falls and broken bones. Muscles are made up of hundreds of thousands of individual fibers, just as a rope is made up of many strands. Each muscle fiber is innervated by a single motor nerve. With aging you lose motor nerves, and with each loss of a nerve, you also lose the corresponding muscle fiber that it innervates. For example, the vastus medialis muscle in the front of your thigh contains about 800,000 muscle fibers when you are 20, but by age 60, it probably has only about 250,000 fibers. However, after a muscle fiber loses its primary nerve, other nerves covering other fibers can move over to stimulate that fiber in addition to stimulating their own primary muscle fibers. A regular exercise program can help to slow the loss of muscle fibers and improve mobility (Physiol Rev, Jan 1, 2019;99(1):427-511). Lifelong competitive athletes over 50 who train four to five times per week did not lose as many of the nerves that innervate muscles and therefore retained more muscle size and strength with aging than their non-athlete peers (The Physician and Sportsmedicine, October 2011;39(3):172-8). Lifelong competitive runners over 60 can have almost the same number of muscle fibers as 25-year-olds.
A key to prolonging your life and preventing disease is to keep on moving. Lying in bed for many hours each day is a certain way eventually to kill yourself. Each day that you spend not moving your muscles weakens your heart, muscles and bones until eventually you can die of heart failure. You do not have to have a specific exercise program (although I recommend having one). You just need to stay active for a large part of each day.
Dr. Gabe Mirkin is a Villager. Learn more at www.drmirkin.com