Factors that impact longevity - Biological, physical, and social
Longevity literally refers to the “length of life” (Merriam-Webster, 2003, p. 726). It encompasses the related concepts of life span, “the maximum number of years and individual can live” and life expectancy, “the number of years that will probably be lived by the average person born in a particular year” (Santrock, 2002, p. 526). Like virtually all other physical and psychological phenomena, longevity is a factor of a combination of heredity and environmental influences – the nature and the nurture.
Some gerontologists have attempted to separate these factors into the distinctive categories of primary aging processes – changes presumed to be genetically programmed (such as brain cell loss) – and secondary aging processes – events and processes that accelerate primary aging, resulting from the lifelong accumulation of insult to one’s body from stress, emotional tension, physical trauma and disease (Selye, 1970; Timiras, 1978; Birren & Schaie, 2001).
Heredity is certainly a key factor influencing an individual’s longevity. In general, an individual’s life expectancy tends to mirror that of his/her close ancestors, within a relatively close range (Hoyer, Roodin, Rybash & Rybash, 2002; Papalia, Camp & Feldman, 1995). Many genetic theorists posit that the rate and progression of biological aging is controlled by a pre-wired genetic program (Hoyer, Roodin, Rybash & Rybash, 2002). Specifically, they argue that the key mechanism contributing to longevity is the genetically based ability of cells to repair age-accumulated damage (strongly influenced by environmental factors) to the DNA molecule, and that the efficiency of this biological repair system varies among hereditary lines (Sacher, 1978; Sacher & Duffy, 1979).
In other words, living ‘to a ripe old age’ tends to ‘run in families’, indicating a strong genetic link. Many aspects of physical/biological health, including, predisposition to illness and disease, body composition, metabolism, etc., are directly related to one’s genetic endowments. These factors seem to serve as a set point for a range within which life choices and environment can influence various health issues (Whitbourne, 2000; Birren & Schaie, 2001).
Additionally, sex differences in longevity have both a biological and a social component. From a biological perspective, females as a whole, in conjunction with the presence of the X chromosome, tend to exhibit more resistance to infections, less tendency toward degenerative diseases and increased production of antibodies in the immune system (Santrock, 2002; Hoyer, Roodin, Rybash & Rybash, 2002).
From the environmental perspective, many factors contribute to longevity (or conversely the lack thereof). Lifestyle patterns, including proper nutrition, medical care, exercise and intellectual stimulation are related to increased life expectancy (Santrock, 2002). Additionally, socioemotional factors such as, comfortable socioeconomic status, satisfying interpersonal relationships and positive self-concept, have also been associated with a longer, healthier life span (Pfeiffer, 2001). Similarly, stress has been implicated in reducing the energy capacity of individuals and contributing to the wear-and-tear explanation of aging. Characteristic differences in temperament play a role in the effects of stress in that stress involves a combination of external events and the internal cognitive and physiological response mechanisms of the individual (Whitbourne, 2000; Birren & Schaie, 2001; Santrock, 2002; Hoyer, Roodin, Rybash & Rybash, 2002).
In a broader sense, cross-cultural differences in longevity are well documented (Whitbourne, 2000; Birren & Schaie, 2001). These differences can be attributed primarily to varying health conditions (i.e., clean and safe water, food supply and sanitation) and availability of adequate health care. Global environmental issues such as hazardous waste disposal, exposure to toxins, pollution and atmospheric deterioration, represent additional issues which can impact the longevity of individuals, especially in high-risk geographic locations (Hoyer, Roodin, Rybash & Rybash, 2002).
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Sacher, G. A. & Duffy, P. H. (1979). Genetic relation of life-span to metabolic rate. Federal Proceedings, 38, 184-188.
Santrock, J. W. (2002). Life-span development, 8e. Boston, MA: McGraw-Hill.
Seyle, H. (1970). Stress and aging. Journal of the American Geriatrics Society, 18, pp. 660-681.
Timiras, P. (1972). Developmental physiology and aging. New York, NY: MacMillian.
Whitbourne, S. K. (2000). Adult development and aging: Biopsychosocial perspectives. New York, NY: Wiley.