While aging is associated with a variety of body changes and an overall tendency towards declining health, there is nothing about the aging process itself that requires elderly people to lose their independence. Rather, it is the various diseases that people become increasingly susceptible to with advancing age that compromise health and independence. Not all older people end up requiring eldercare; for the most part, only those who become ill in their old age will require substantial elder care.
Eldercare becomes necessary when elders start to find it difficult or impossible to go about their activities of daily living (ADLs) safely and independently. Elders' activities of daily living usually become compromised as a result of health problems they develop. All types of health conditions can compromise independence, including physical conditions, mental or cognitive conditions (involving memory or attention), and even emotional conditions.
Elders' care requirements are determined by several factors, including the type of health conditions they develop, the severity of those conditions, the types of deficits caused by those conditions, and the natural course (or prognosis) of those conditions. While it is obvious that more severely ill elders will require more care than healthier elders, there are some distinctions that must be considered. Minor appearing illnesses may result in hard to detect but very real physical or brain deficits that could cause an elder to no longer be competent to drive a car, for example, or to have memory problems that compromise their ability to remember to take pills. Additionally, the natural course of elders' illnesses must be taken into account when planning for care; whether or not an illness will cause a progressive weakening of elders' abilities, or whether their condition is likely to be stable.
Some health conditions (stroke, for example) are static, stable and relatively unchanging in nature. Such conditions may have a profound impact on elder's ability to care for themselves, but they are more or less one time events. If no new strokes occur, it is unlikely that stroke patients' functioning will continue to decline. Other kinds of illnesses are progressive in nature, meaning that they get worse over time. Elders with progressive conditions will require a more ongoing care planning process take place then will elders with more static conditions.
Finally, it must be noted that different health conditions produce different health effects and thus will require different types of care to be made available. For example, elders who lose partial mobility due to a physical impairment will likely require transportation and shopping assistance, and possibly some adaptive technology (such as a motorized wheelchair) but may otherwise be quite capable of continuing to live alone. In contrast, elders who lose their memory and thus their ability to be responsible - to organize and monitor their own lives - will likely require more constant supervision to insure their safety.