Charles River Wheelers

Weak Muscles Predict Dementia

2023-11-22 1:44 AM | Anonymous

By Doctor Gabe Mirkin  (This article is curtesy of Dr. Mirkin)

A study of 1275 people found that those who had very weak hand grip strength had signs of accelerated aging, as measured by deterioration of the DNA in their cells (J Cachexia, Sarcopenia and Muscle, Feb 2023;14(1):108-115). The authors of this study cited earlier studies showing that grip strength appears to be a better predictor of life expectancy than blood pressure. Muscle weakness also predicts increased risk for:
• physical disability in older people (J Nutr Health Aging, 2018;22:501-507; Ethn Health 2017;26:1-12)
• long-term disability and development of chronic diseases (Exp Gerontol, 2021;152:111462)
• dementia (Clinical Interventions in Aging, July 5, 2018;13)
• cancer (Cancer Med, Jan 2022;11(2):308-316)
• heart attacks (J of Epidem & Comm Health, Nov 11, 2020;74(1):26-31)
• premature death (J Am Med Dir Assoc, May 2020;21(5):621-626.e2)

Five percent of people in their seventies, 25 percent in their eighties, and almost 40 percent of people in their nineties suffer from some level of dementia. One study of more than 5000 people, average age over 70, found that low muscle size is associated with increased risk for dementia (Age and Ageing, March 2017;469(2):250-257). Many studies show that excess belly fat is a major predictor for dementia, but lack of muscle size and strength appears to be an even stronger predictor of dementia than having excess belly fat (Clinical Interventions in Aging, July 5, 2018;13).

Home Test to Predict Risk for Dementia
You can get a simple Grip Strength Tester at Amazon and other retailers. A male’s average grip strength rating should be 105 or higher, while a woman’s average grip strength rating should be 57 or higher. I realize that a falsely weak handgrip test could cause needless concern. I recommend that if you are worried about your hand strength, check with your doctor who can order a more complete workup if needed.

You can expect to lose muscle size and strength as you age. Between 40 and 50 years of age, the average person loses more than eight percent of their muscle size. This loss increases to 15 percent per decade after age 75. The people who lose the most muscle usually are the least active, exercise the least and are the ones who die earliest. Older people who lose the most muscle are four times more likely to be disabled, have difficulty walking, and need walkers and other mechanical devices to help them walk (Am J Epidemiol, 1998; 147(8):755-763).

Your muscles are made up of thousands of muscle fibers, just as a rope is made up of many strands. Every muscle fiber is innervated by a single nerve fiber. With aging you lose nerves, and when you lose a nerve attached to a muscle fiber, that muscle fiber is lost also. A 20-year-old person may have 800,000 muscle fibers in the vastus medialis muscle in the front of his upper leg, but by age 60, that muscle would have only about 250,000 fibers. For a 60-year-old to have the same strength as a 20-year-old, the average muscle fiber needs to be three times as strong as the 20-year-old’s muscle fibers. You cannot stop this loss of the number of muscle fibers with aging, but you can enlarge each remaining muscle fiber and slow down the loss of strength by exercising muscles against progressive resistance (Experimental Gerontology, August 13, 2013).

My Recommendations
Strength training, aerobic exercise and a healthful diet can help to slow the frightening loss of muscle size and strength in people as they age (Clinical Interventions in Aging, August 6, 2015;1267-1282). I believe that everyone who is able should do some form of resistance exercises to increase their muscle size and strength. If you are not already doing strength training exercise, first check with your doctor to make sure you do not have any condition that may be harmed by exercise. Then see Resistance Exercise You Can Do at Home. I recommend that you hire a knowledgeable personal trainer at least for a few sessions to set up your home program and help with choices of equipment. I also recommend lifting light weights with more repetitions, because lifting lighter weights many times is less likely to cause injuries than lifting heavier weights a few times.

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