Chronic illnesses play a major role.
Sarcopenia, the age-related loss of muscle, is a key factor of the central problem. But it's never too late to start exercising. There are strategies anyone can design no matter what age, no matter what physical condition. Study after study has demonstrated that the single most important activity a person can do to slow down and even reverse the aging process is to exercise. For some people this might be as simple as taking a 30-minute walk once a day.