![]() ![]() ![]() These two measures of disease frequency (incidence and prevalence) provide different information, and both are important-one for an understanding of the population risk (incidence) and one for an understanding of the burden (prevalence) of a particular disease. Morbidity data reflect either the incidence (new cases) of a disease over a fixed period or its prevalence (total cases) at a given time, depending on the study design or the method of data collection. For example, the role of specific intrinsic and extrinsic factors in adult-onset diabetes mellitus has been extensively investigated, but further studies are needed for an adequate understanding of the relative importance and interaction of endogenous and exogenous factors in the disease.īoth morbidity and mortality data can be used to evaluate the association of disease with age in the elderly population (65 and over). The association of disease susceptibility with age-which might be related to intrinsic factors, extrinsic factors, or some combination-needs to be assessed for each disease. In others, time and age-associated exposure characteristics, such as obesity and duration of exposure, are the direct factors, and not age itself. The role of age as a factor associated with increasing incidence appears to be direct (or independent) in some diseases. Table 6–1 presents some examples.Īge-specific incidence rates for female breast cancer in four population groups. It also discusses evidence of age-associated changes in normal functions, such as vision, bone metabolism, and the immune system. This chapter reviews some of the animal and human studies on the relationships of the environment with age-associated diseases in specific organ systems. Controlled studies of animal populations are also needed to determine both the natural occurrence of diseases with aging and changes in immune response and in metabolic and kinetic responses to xenobiotics throughout the life cycle. Although there are reasonable theoretical grounds for expecting some disease patterns to be normal functions of age, additional research needs to be done to clarify possible mechanisms. Thus, exposures to carcinogens or neurotoxins in infancy and childhood (or in old age) might produce stronger responses than those occurring in the middle stages of life. Susceptibility to disease changes throughout the human life cycle and is believed to be a function of many factors, including changes in the immune system and in the rate of cellular division. For other diseases, such as those reflecting cumulative, chronic exposures, rates might increase with age. For some diseases, such as those for which early antigenic stimulation produces lifelong immunity, resistance usually increases and incidence falls with age. Biologic changes associated with aging can reasonably be expected to be associated with parallel changes in susceptibility to disease. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |