The Impact of Decreased Physiologic Reserve
Older adults have lower physiologic reserve in each organ system when compared with younger adults, placing them at risk for more rapid decline when faced with acute or chronic illness.
Some contributors to decreased physiologic reserve may include decreases in muscle mass and strength, bone density, exercise capacity, respiratory function, thirst and nutrition, or ability to mount effective immune responses. For these reasons, older adults are often more vulnerable, for example, to periods of bedrest and inactivity, external temperature fluctuations, illnesses that are otherwise self-limited in younger adults, and complications from common infectious diseases. Although preventive measures, such as vaccinations, may be beneficial, decreased physiologic reserve may also impair older adults’ ability to mount an effective immune response to vaccines. These processes can also delay or impair recovery from serious events or illnesses such as hip fractures or pneumonia. As a result of the interplay of multiple medical conditions in the context of decreased physiologic reserve, older adults are prone to developing complex geriatric syndromes, such as frequent falls.