Bears emerge from months of hibernation with their muscles largely intact. Not so for humans, who, if bedridden that long, would lose so much muscle they would have trouble standing. Why muscles wither with age is captivating a growing number of scientists and drug and food companies, and people who are confronting the body’s natural loss of muscle tone.
With interest high among the ageing, drug companies already are trying to develop drugs that can build muscles or forestall their weakening without the notoriety of anabolic steroids. Food giants like Nestle and Danone are exploring nutritional products with the same objective.
In addition, geriatric specialists are trying to establish the age-related loss of muscles as a medical condition under the name sarcopenia. Muscle strength is key. Researchers involved in the effort say doctors and patients need to be more aware that muscle deterioration is a major reason the elderly lose mobility and cannot live independently.
“There is no medical terminology that’s been created and made uniform to allow the doctor to make a diagnosis, look at possible causes, and make a treatment plan,” said Dr Studenski, a professor of medicine.
Experts say sarcopenia affects about 10 per cent of those older than 60, with higher rates as age advances. Causes of the loss of muscle mass or strength might include hormonal changes, sedentary lifestyles, oxidative damage, infiltration of fat into muscles, inflammation and resistance to insulin.
Some problems stem from the brain and nervous system. The best approach to restoring or maintaining muscle mass and strength is exercise, particularly resistance training. The National Institute on Aging is now sponsoring a controlled trial to test whether exercise can prevent disability in largely sedentary people, age 70 to 89. There is also some early evidence that nutrition, like vitamin D or high levels of protein, might help.
Muscle mass can be measured by the same scans used for bone density. But some studies have shown that strength, such as gripping force, or muscle function, as measured, say, by walking speed, can be more important than mass in predicting problems seniors might have.
So the definition is shifting to include muscle strength and function. Experts say that to win approval from regulators, a drug must improve walking ability or prevent people from falling. Or perhaps it could restore mobility faster after a person is bedridden. Older people can lose so much muscle during a prolonged hospital stay that they have to move to a nursing home.