Medical brain notes 30

  AGING AND DISEASE INTRODUCTION Aging  is difficult to define but is perhaps most widely understood to be adecrease in the ability to survive. As people age ( Figure 18.1 ), they are less able to perform strenuous physical activities which were relatively easy when they were younger. With aging comes a decline in the function of most organs in the body, making elderly people more susceptible to disease. Indeed, most major diseases of the developed world, such as coronary heart disease , cancer , and diabetes type 2 are age-related. With aging comes  senescence , that is, a decline in functions of almost all parts of the body and at all levels of organization, from cells to organ systems. Senescence changes may be responsible for some disease of old age or may increase susceptibility to certain diseases. Thus elderly people make up a large proportion of patients in hospitals and in most countries a high proportion of the health budget is devoted to the care and treatment ...

  AGING OF CELLS, TISSUES, ORGANS AND SYSTEMS The deleterious effects of the aging processes are numerous and diverse. They affect cells, tissues, organs and systems. CELLS Cellular functions decline in efficiency with advancing age. For example, the abilities of mitochondria to survive a hypoxic insult and perform oxidative phosphorylation, the synthesis of structural, enzyme and receptor proteins, the abilities of cells to take up nutrients and repair chromosomal damage all decline with age. Aged cells also have irregular and abnormally shaped organelles, particularly nuclei, Golgi apparatus and endoplasmic reticulum and accumulate waste products. TISSUES All tissues are affected with age. For example, muscle mass is subject to a condition known as muscle atrophy due to a reduction in size of muscle groups and to losses of individual muscle fibers. This results in a decreased capacity for work. Other factors, such as cardiovascular, respiratory and joint functions, also influence...

  CAUSES OF AGING A number of theories have been proposed to explain cellular aging. These theories can be divided into two broad groups: those that are based on ‘wear and tear’ and those that propose a genetic basis. ’WEAR AND TEAR’ THEORIES ‘Wear and tear’ theories suggest that aging processes in cells are due to a continual exposure to harmful agents from both inside and outside the cell throughout life. These agents include: free radicals, glycated proteins, waste products and products of erroneous biosynthesis, the error-catastrophe theory. Free radicals Free radicals are molecules that have an unpaired electron. This makes them highly reactive although they can be stabilized by the donation of electrons to, or removal from, other molecules. As a result of this process new radicals are produced and a chain reaction can be propagated. Free radicals are produced in phagocytic cells in processes aimed at destroying pathogens. They may also be produced during endogenous enzymatic ...

  AGE-RELATED DISEASES Factors that may contribute to causing disease in the elderly include the physiological and biochemical changes associated with normal aging, the cumulative exposure to harmful agents, and an increased sensitivity to agents or the environment. A number of diseases in particular show an increased incidence in older people. These include cancer, cardiovascular disease, type 2 diabetes, cataracts, arthritis, Parkinson’s disease and Alzheimer disease. The latter, and Hutchinson-Gilford syndrome, which affects children.. CANCER In general, the incidence of most cancers increases with age ( Figure 18.10 ) with more than half of all cancers occurring in people over the age of 65 years. Two main hypotheses have been proposed to explain the link between cancer and age. First, an age-related accumulation of carcinogenic substances may increase the incidence of cancers in the elderly. This process is independent of the senescence changes described above that occur in th...

  CALORIE RESTRICTION AND AGING A reduced energy intake (‘calorie restriction’) is known to slow down the rate of aging and onset of age-related disorders, such as cancer (breast, lymphomas, prostate), nephropathy, cataract, diabetes, hypertension, hyperlipidemia and autoimmune diseases. This has been demonstrated in a variety of species including chickens and rodents and is also believed to be true for humans. The effects of calorie restriction were demonstrated in the 1930s using laboratory rats. Rats were divided into two groups. One group was allowed to feed freely while the other was fed on a diet containing 30% of the calories of the first group, although they were provided with sufficient protein, fats, vitamins and minerals to maintain normal health. The calorie-restricted rats lived for four years compared with three years for those allowed to feed freely .  In addition, the calorie-restricted rats developed fewer age-related diseases. Studies on calorie restriction h...

  INVESTIGATIONS AND MANAGEMENT OF THE ELDERLY Investigation and management of illness in the elderly poses a number of problems. Many conditions are more common in the elderly and often the presentation of some of these diseases may differ from that in younger people. For example, diabetes mellitus in the elderly often presents as a complication of, for example, renal failure or impaired healing of wounds, instead of the classical signs of polydipsia or polyuria first seen in younger patients. Elderly people, particularly those with poor mobility, may also suffer from poor nutrition. Furthermore, they are often on multiple medications that may affect test results. The high incidence of many diseases in the elderly population justifies screening programs for such conditions to increase the chances of detecting disease at a more treatable stage. Clinicians, hospitals and geriatric clinics can all carry out screening. Some of the common investigations are listed in  Table 18.1 ....