Free radical theory of ageing: Applications

Abstract Ageing is the accumulation of changes that increase the risk of death. Ageing changes can be attributed to development, genetic defects, the environment, disease, and the inborn ageing process. The major contributors of ageing changes after age 28 in the developed countries are endogenous chemical reactions, which, collectively, exponentially increase the chance of disease and death with advancing age. These reactions constitute the “inborn ageing process”. This process is the major risk factor for disease and death of the 98–99% of cohorts still alive at age 28 in the developed countries, where living conditions are near optimum. In these countries average life expectancies at birth (ALE-B) range from 76–79 years, 6–9 years less than the limit of about 85 years imposed by ageing. The Free Radical Theory of Ageing (FRTA) postulates that ageing changes are caused by free radical reactions. This theory suggests the possibility that measures to decrease the rate of initiation and /or the chain length of free radical reactions may, at least in some cases, decrease the rate of reactions which produce ageing changes without significantly depressing those involved in maintenance and function. Many studies support this possibility. Applications of the FRTA have been fruitful. For example, it is a useful guide to the efforts to increase the life span, and it provides plausible explanations for ageing phenomena, (for example, the association of disease with age as well as insight into pathogenesis, the gender gap, the association between events in early life and late onset disease, and the shortening of telomeres with cell division). Further, it is reasonable to expect on the basis of animal and epidemiological studies, that the increasing population-wide use of antioxidant supplements and ingestion of foods high in antioxidant capacity over the past 40 years have helped to increase the functional life span in the U.S.A. by contributing significantly to the decline in “free radical diseases”, to increases in the fraction of elderly in the population, and to the decline in chronic disability in this group.