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Genetic & Environmental Factors in Longevity

Everyone wants to live longer, and because of this the question of what causes some humans to live longer than others has always been of interest to science and medicine. Environmental factors such as disease, violence and lifestyle obviously play a role. Now that the human genome has been mapped, scientists have been able to start examining more closely the role played by genetics.

  1. Primary Environmental Factors

    • For the purposes of health and longevity, lifestyle activities such as work, exercise and diet are considered environmental factors. According to MIT "Technology Review" research on the Seventh-Day Adventists shows that members of the church have an average life expectancy of 88 years. Seventh Day Adventists because of their religious beliefs don't smoke, drink alcohol or eat meat and devote their weekends to religious services and family activities. These activities both maintain their health and keep their stress levels low. Diet, exercise, smoking, alcohol consumption, exposure to pollution and other environmental factors are known to be significant in determining longevity.

    Biological Clock

    • As early as the 18th century, long before genetics was clearly understood, Georges-Louis Leclerc, Comte de Buffon speculated about the existence of a "biological clock" which determined the length of a person's life if nothing happened to prematurely shorten that life. The biological clock theorists suggested that beyond a certain age, generally 85, there would be a rapid acceleration in the number of deaths by natural causes. A 1996 article -- Determinants of Longevity: Genetic, Environmental and Medical Factors -- published in the "Journal of Internal Medicine," disputes the theory though. Its authors point out that studies of the Odense Archive of Population Data on Ageing, which monitors deaths worldwide, shows that after age 80 individuals are less likely to die of natural causes than younger individuals. In other words, compared to the population as a whole, 80 year olds are more likely to live to 100 than the general population. Additionally the number of individuals living to see the 80-to-100 age range has been increasing for several decades.

    Predisposition to Disease

    • Certain individuals appear to be genetically more likely to contract a variety of diseases than others. This includes diseases such as muscular dystrophy, Lou Gehrig's disease (amyotrophic lateral sclerosis) and lupos, as well as more common diseases such as cancers, heart disease, hypertension and even dementia and Alzheimer's disease. According to Nicholette Zeliadt of "Scientific American," this predisposition to disease, or the lack of it, appears to be the primary genetic factor in determining longevity in all age groups.

    70/30 Split

    • According to "Scientific American," a 2010 study led by Paola Sebastiani and Thomas Perls, professor of medicine and geriatrics, both of Boston University, determined that both genetics and environmental factors play a large role in determining longevity, but of these, environmental factors are the most important. The study examined the DNA of 800 subjects between the ages of 95 and 119 and compared it to the DNA of a random sampling of the population as a whole. It concluded that only 20 to 30 percent of an individuals' chances of reaching age 85 is determined by genetics, with the rest being determined by lifestyle and environment.

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