Aging in Today's Environment (1987) / Chapter Skim
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Executive Summary
Executive Summary
Pages 1-9
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From page 1... ...
. Several relationships must be considered the impact of intermittent or lifelong exposure to environmental agents an the rate of aging, the impact of lifelong exposure on health status when one reaches more advanced age, and the special response of the aged compared with that of the young when exposed to environmental agents.
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But the amount of the decline caused by lifetime exposure to harmful environmental agents and the amount caused by basic, underlying aging processes are questions of great theoretical and practical significance, given the demographic patterns that show an increasing percentage of older persons in the population. Although the increased incidence of chronic diseases is often associated with aging, such diseases need not be characteristic of the aging processes.
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Diet moclulates many adverse effects normally associated with aging, and some dietary regimens actually promote such effects. For instance, a few studies with rodents on a restricted food intake but with ample intake of essential nutrients and other substances for which there is some evidence of antiaging action showed increased longevity.
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For example, the peak in incidence of Hodgkin's disease in the third decade of life suggested an infectious origin for one kind of Hodgkin's disease, and the plateau in incidence of breast cancer around the ages of 45-55 suggested that the cessation of ovarian function had an effect on the development of the disease. Data on the premenopausal and postmenopausal incidence of breast cancer in different countries suggested that environmental factors play an important role in the etiology of postrnenopaus~ breast cancer, whereas genetic, endocrinologic, and other endogenous factors strongly influence the risk of premenopausal disease.
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The qualitative and quantitative differences in the ways older people tend to respond to drugs result from at least two circumstances: multiple chronic diseases are the rule, rather than the exception, and diseases are accompanied by important and sometimes subtle physiologic changes that occur with normal aging. That is, In addition to the normal age-associated changes in the immune system that affect one's ability to ward off disease, alterations in pharmacokinetics and pharmacodynam~cs alter the response to drug exposures.
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By slightly reducing the dosage of potent drugs with low therapeutic indexes or by watching such patients especially carefully, physicians can ensure the therapeutic efficacy of prescribed medications and detect undesirable drug-related side effects early. AGING AND ENVIRONMENTAL FACTORS Among the best documented examples of age-associated pathologic conditions that are related to environmental factors is photoaging the changes in skin appearance and function that are due to habitual exposure to the sun, rather than to the passage of time alone.
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Because the nervous system appears to have a number of components that are vulnerable both to the aging processes and to toxic chemicals, older people with compromised neural structure and function, as well as reduced capacity for liver metabolism and renal clearance, are probably more susceptible to some neurotoxic substances than are younger adults. In addition, it is generally believed that the clinical expression of disordered neural function resulting from aging or chemical toxins becomes evident only after the considerable structural and functional redundancy of the nervous system has been overcome.
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From page 8... ...
In vitro models are economical and efficient, permit repeated assays and the sharing of common stock among different laboratories, and can be used to investigate cell-cell interactions, such as metabolic cooperation and transformation; however, they cannot completely eliminate the need for experimentation with intact animals. Invertebrates have short life spans, are relatively easy to use, and are relatively inexpensive; many have been widely used as models for the study of aging and meet the proposed criteria for models.
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The extent to which major age-related diseases (e.g., cancer, arteriosclerosis, diabetes, osteoarthritis, osteoporosis, cataracts, hearing loss, amyotrophic lateral sclerosis, Parkinson's disease, and senile dementia of the Alzheimer's type) are coupled to underlying aging processes or environmental influences constitutes an important research question, in light of the surge in the size of this segment of the population.
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