The trunk becomes shorter. The spine is made up of bones (called vertebrae); between each bone is a gel-like cushion (intervertebral disk). The disks gradually lose fluid, making them thinner. In addition, vertebrae lose some of their mineral content, making each bone also thinner. The spinal column becomes curved and compressed (packed together). Bone spurs may also form on the vertebrae, caused by aging and overall use of the spine.

The shoulder blades (scapula) and other bones may become porous (on an X-ray they may look "moth eaten"). The foot arches become less pronounced, contributing (slightly) to height loss. The long bones of the arms and legs, although more brittle because of mineral losses, do not change length. This makes the arms and legs look longer when compared to the body.

The joints become stiffer and less flexible. Fluid in the joints may decrease, and the cartilage may begin to rub. Minerals may deposit in some joints (calcification); this is common in the shoulder. Hip and knee joints may begin to lose structure (degenerative changes). The finger joints lose cartilage and the bones thicken slightly. Finger joint changes are more common in women, and may be hereditary. Some joints, such as the ankle, typically have little change with aging.

Lean body mass decreases, caused in part by loss of muscle tissue (atrophy). The rate and extent of muscle changes seems to be genetically determined. Muscle changes often begin in the 20's in men and the 40's in women.
 

Lipofuscin (an age-related pigment) and fat are deposited in muscle tissue. The muscle fibers shrink. Muscle tissue is replaced more slowly, and lost muscle tissue may be replaced with a tough fibrous tissue. This is most noticeable in the hands, which may become thin and bony. Muscle tissue changes, combined with normal aging changes in the nervous system, cause muscles to have reduced tone and contractility. Muscles may become rigid with age, or may lose tone even if exercised regularly.

EFFECT OF CHANGES

Bones become brittle and are broken easier. Height decreases, primarily caused by shortening of the trunk/spine.

Inflammation, pain, stiffness, and deformity result from breakdown of the joint structures. Almost all older people are affected by joint changes, ranging from minor stiffness to severe arthritis.  The posture becomes progressively stooped (bent) and the knees and hips are more flexed. The neck becomes tilted, and the shoulders narrow. The pelvis, on the other hand, becomes wider.

Movement slows and may become limited. The walking pattern (gait) becomes slower and shorter. Walking becomes unsteady, and there is less arm swinging. Fatigue occurs more readily, and overall energy may be reduced.

Strength and endurance change. Loss of muscle mass reduces strength. However, endurance may be enhanced by changes in the muscle fibers. Aging athletes (with healthy hearts and lungs) may find that performance improves in events that require endurance, and decreases slightly in events that require short bursts of high-speed performance.

COMMON PROBLEMS

Osteoporosis or bones that are below normal density is a common problem, especially for older women. Broken bones occur more readily, and compression fractures of the vertebrae can cause pain and reduce mobility.

Muscle weakness contributes to fatigue, weakness, and reduced activity tolerance. Joint problems are extremely common. This may be anything from mild stiffness to debilitating arthritis (see osteoarthritis).  Injury risk is greater because of falls related to gait changes, instability, and loss of balance.

Sometimes, elderly people have reduced reflexes. This is most often caused by changes in the muscles and tendons, rather than changes in the nerves. Decreased knee jerk or ankle jerk are not unexpected. However, some changes (such as a positive Babinski's reflex) are ALWAYS considered abnormal.

Involuntary movements (muscle tremors and fine movements called fasciculations) are more common in the elderly. Inactive or immobile elderly people may experience weakness or abnormal sensations (paresthesias). Muscle contractions or inability to move a muscle may occur in those unable to move voluntarily or to have their muscles stretched through exercise. Restless leg syndrome may occur.

BODY CHANGES

Fat (adipose) tissue is increasingly deposited toward the center of the body, including around the abdominal organs. The adipose under the skin (subcutaneous fat) is decreased. Lean body mass also decreases. The muscles, liver, kidney, and other organs lose some of their cells (atrophy). Bones lose some of their minerals and become less dense. Tissue atrophy decreases the amount of water in the body.

Height progressively decreases. The tendency to become shorter occurs among all races and both sexes. Height loss is related to aging changes in the bones, muscles, and joints. The average height loss is 1 centimeter (about 0.4 inches) for every 10 years after age 40, and height loss is even greater after 70 years old. In total, aging may cause a loss of 1 to 3 inches in height.

Men often gain weight until about age 50, then begin to lose weight. Women usually gain weight until age 70, then begin to lose weight. Weight loss is, in part, caused by a loss of muscle tissue. Some weight loss is caused by loss of subcutaneous fat stores. Part of the weight loss is caused by loss of bone tissue. Loss of body water also contributes to weight loss. If your appetite is poor (which is common among many older people), weight loss can be even more pronounced.

FACIAL CHANGES

Just like the rest of the body, the typical appearance of the face and neck changes with aging. Muscle tone is lost, causing a flabby or droopy appearance. The jowls may begin to sag, contributing to a "double chin" in some people. The nose lengthens slightly and may look more prominent. There is an increase in the number, size, and color of pigmented spots on the face. The skin thins, becomes dry, and wrinkles develop.

HAIR CHANGES

Hair color change is probably one of the most obvious signs of aging. Hair color is caused by a pigment (melanin) that is produced by the hair follicle. With aging, the follicle produces less melanin. Graying often begins in the 30's although this age varies. Graying usually begins at the temples and extends to the top of the scalp. Hair becomes progressively lighter, eventually turning white. By the time they are in their 40's, about 40% of all people have some gray scalp hair. Body and facial hair also turn gray, but usually later than scalp hair.

Many of the hair follicles stop producing new hairs. Both men and women lose hair as they age. About 25% of men begin to show some signs of baldness by the time they are 30 years old, and about two-thirds are either bald or have a balding pattern by age 60. Men develop a typical pattern of baldness associated with the male hormone testosterone (male-pattern baldness). Hair is lost first from the front and top of the scalp.

CHANGES IN LUNGS

An average person continues to slowly make new alveoli until about age 20. After this age, his lungs begin to lose some of their tissue. The number of alveoli decreases, and there is a corresponding decrease in lung capillaries. The lungs also become less elastic due to various factors including the loss of a tissue protein called elastin.

Changes in the bones and muscles result in a slightly increased front-to-back chest diameter. Loss of bone mass in the ribs and vertebrae, and mineral deposits in the rib cartilage, change the spine curvature. There may be side-to-side curvature (kyphosis) or increased front-to-back curvature (scoliosis).

The maximal force one can generate on inspiration or expiration decreases with age as the diaphragm and muscles between the ribs (intercostals) becomes weaker. The chest is less able to stretch to breathe, and the pattern of breathing may change slightly to compensate for decreased ability to expand the chest.

SENSORY CHANGES

When you age, the way your senses (taste, smell, touch, vision, and hearing) are able to give you information about the world changes. Your senses become less acute, and you may have trouble distinguishing details.
 

Sensory changes can have a tremendous impact on your lifestyle. You may have problems with communication, enjoyment of activities, and social interactions. Sensory changes can contribute to a sense of isolation.