ABSTRACT
Ageing implies a decreased viability or an increased vulnerability to stress with a diminished ability to maintain homeostasis. The World Health Organization regards people in the age range 45-59 years as ‘middle aged’, 60-74 as ‘elderly’, 75-89 as ‘old’ and over 90 as ‘very old’. Anatomical and physiological changes with ageing usually begin in middle life in almost every body system (Fig. 15.1), but their magnitude and clinical significance vary considerably. There is considerable confusion about what is part of the ageing process and what is due to disease. The exact cause of ageing is unknown. It has been suggested that cellular ageing may occur as a result of some alteration in the information carried by DNA, or by programmed cell death. Other theories of ageing suggest that the changes result from wear and tear, accumulation of substances such as lipofuscin, collagen, amyloid and calcium in abnormal sites, progressive reduction of endocrine function and altered immune function.
