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‘To me, old age is fifteen years older than I am’ (Bernard Baruch (1870–1965), quoted in an interview when he was 85 years old). Definitions of what constitutes old age are naturally somewhat arbitrary, even if we cannot accept Baruch's definition. Hippocrates, the Greek physician regarded as the father of medicine, divided old age into five categories. Up to 70 years, he described as the springtime of old age, 70–75 years as green old age, and 75–80 as real old age. The years 80–90 he considered ultimate old age and over 90 he
Salivary secretion is often reduced in the elderly. This can cause dysphagia which, together with a reduction in the sensitivity of the taste buds, may lead to a loss of appetite and enjoyment of certain foods. Over time, the resulting alterations in diet may contribute to malnutrition. Age-related changes are also seen throughout the GI tract. For example, small intestinal villi shorten, thereby reducing the surface area available for absorption, and the motility of the colon and rectum is reduced. The latter may lead to constipation, which can in turn exacerbate problems of fecal incontinence.
Cardiovascular changes associated with aging free medical books
There are subtle changes to cardiovascular function throughout the normal lifespan. These appear to be related to a gradual decline in the ability of the body to exert control over the heart and blood vessels as well as to specific alterations of cardiac and vascular properties. Although resting heart rate alters little throughout life, there is a gradual reduction in both the intrinsic heart rate (in the absence of any autonomic stimulation) and the maximum heart rate that can be achieved. At the age of 45 years, maximum achievable heart rate is about 94 per cent of that at 25 years, while at 85 years this figure has fallen to 80 per cent. These changes are caused by a loss of pacemaker cells in the sinoatrial node as they become replaced by fibrous tissue. The ability of the heart to respond to challenges such as heavy exercise is thus limited. While resting stroke volume does not appear to change with age, the ability of the heart to increase stroke volume is reduced. This effect, coupled with the reduced maximal heart rate, brings about a fall in the maximum cardiac output achievable. Valvular thickening and calcification may further reduce the efficiency of the heart.
Figure 31.2 illustrates typical age-related changes in systemic arterial blood pressure. Between the ages of about 40 and 70 years systolic pressure rises from an average of 16 kPa (120 mmHg) to an average of around 22.5 kPa (170 mmHg), while diastolic pressure increases from about 10.7 kPa (80 mmHg) to around 12.5 kPa (90–95 mmHg). The increase in systolic pressure is probably due to decreased aortic compliance and a loss of elasticity, while the increase in diastolic pressure may reflect an increased total peripheral resistance, probably caused by narrowing of the blood vessels. After the age of 75 or so, blood pressure begins to fall again, perhaps because of a gradual reduction in the strength of contraction of the myocardium. Elderly people also show a reduced baroreceptor response and this frequently results in postural hypotension on moving from a supine to an upright position. Old people may feel dizzy for a while after standing up, and many falls may be attributed to this delay in restoration of normal blood pressure.
The progressive increase in blood pressure with age. On the left, the figure shows the trend for a cross-section of the male population. On the right, the changes fora group of male subjects at three different ages (a longitudinal study) are shown. The trend in women is similar.
Changes in respiratory function medical book Although some older people suffer from chronic respiratory illnesses as a result of smoking or industrial disease, alveolar function is relatively unchanged with age. The most noticeable changes to the respiratory system include a gradual reduction in lung compliance associated with a loss of elasticity and a reduction in the strength of the muscles of the ribcage. Consequently, there is an increase in the work of breathing, a fall in vital capacity, and an increase in residual volume. Closing volume increases with age and may encroach upon the normal tidal volume. Usable lung capacity typically falls to around 82 per cent of its maximum value by the age of 45, to 62 per cent at the age of 65, and to around 50 per cent by the age of 85. Over time, some alveoli are replaced by fibrous tissue and gas exchange is reduced, so that arterial Po2 declines with age (Fig. 31.3). There may be a small rise in arterial Pco2, particularly during exercise. Overall, the respiratory changes seen in the elderly tend to limit the ability to increase ventilation and oxygen delivery to tissues during periods of increased demand such as exercise.
The fall in arterial Po2 with age. Note that not all healthy young subjects achieve the theoretical value of 13.3 kPa (100 mmHg). However, even when Po2 has fallen to around 10.6 kPa (80 mmHg), there is adequate oxygenation of the arterial blood.
