: Targeted exercises can help maintain the thenar muscles. Using a soft stress ball or practicing "thumb-to-finger" touches can keep the intrinsic muscles active.
: Caloric deficits and certain nutritional deficiencies can accelerate the loss of fat and muscle in the hands, making them appear prematurely aged. How to Maintain Hand Health and Appearance mature skinny thumb
One of the most common changes in aging skeletal muscle in the body is the major reduction in muscle mass ranging from 25% to 45%, Physiopedia How to Lose Finger Fat and Make Your Hands Look Slimmer : Targeted exercises can help maintain the thenar muscles
The appearance of a thinner, more prominent-looking thumb in older adults is typically driven by a combination of muscle loss and skin changes: How to Maintain Hand Health and Appearance One
: The base of the thumb is a common site for arthritis. While it can cause swelling, the associated muscle wasting from lack of use can lead to a thinner appearance in the surrounding areas.