A number of physiological changes occur as we grow older. Some of the common changes that we thought represented aging have turned out to be the result of disease. Most of the normal changes of aging have no impact on normal functioning, although they become apparent when the body is placed under stress (e.g., acute illness, physical exertion). For example, the maximum heart rate of older adults is lower than that of younger adults. However, the resting pulse of a younger and older adults would not show this change. It is important to be able to recognize the changes of normal aging versus the effects of disease. Untreated disease can result in "excess disability" and reduce the quality of life of individuals. In this lecture we identify and describe the most important changes in the body that occur with aging. Healthy aging is an issue of increasing importance as the size of the older population continues to grow. Poor health in later life is not inevitable. Much of the illness and disability associated with aging is related to modifiable lifestyle factors that are present in middle age.

Diseases make old age miserable, not the normal changes of aging.

Although we have more wrinkles, more grey hair, and stiffer arteries the normal changes of aging are unlikely to kill us. No one dies of old age, not even Jeanne Calment in France who died at age 122! Infections or other diseases, most of which might are not life threatining when you are young, are the usual cause of death in old age.

Normal changes of aging reduce your capacity to respond to illness.

Injuries or infections that only slowed you down when you were young can cause disability and dependency when you are old. An acute illness can cause a "cascade of health problems" that can lead to rapid declines in health and function.

Aging diminishes your body's ability to adapt.

Older adults are more vulnerable very cold or very hot weather because they are unable to adapt their body temperature as effectively.

Heterogeneity increases with age.

Everyone ages differently and the rate of aging can vary markedly in individuals. Age-related changes in one system are not predictive of changes in other systems. For example, you may have cataracts in your eyes that severely restrict vision and yet have excellent heart function. In addition, an older person does not age faster than someone who is younger. However, biological age is different from chronological age. Thus, there is tremendous diversity among individuals of similar chronological age. A physically fit 50 year old can have the functional capacity of a thirty year old while someone who smokes and is sedentary may function as if they were several decades older.