Aging

Proximity to Death

No one knows when exactly he or she will die. Nevertheless, aging as an indicator of proximity to death is not simply an arbitrary guess. Rather, the risk of mortality (i.e., risk of an individual dying) changes systematically for each species. Fruit flies have a greater risk of dying within weeks than do mice or humans.

Thus, an increase in the risk of death is sometimes considered the benchmark for the onset of aging. The U.S. Social Security Administration Period Life Table shows the proportion of people in each age group who died in a given year. Life insurance companies use similar “actuarial” statistics.

For example, the likelihood that a 1-year-old male in the United States will die is 4 out of 10,000. The risk for a 6-year-old male drops to 1.5 out of 10,000. And the risk that a 10-year-old will die is only 9 out of 100,000. Every year after age 10, the risk of death increases. This information illustrates the rate at which individuals begin to accrue health or system problems associated with risk of death and that may be an indicator of aging.

Of course, there are several dilemmas to using the odds of survival to indicate aging. Among humans, age 10 does not represent the onset of reproductive maturity for most individuals, let alone declines that we typically think of as aging. Although mortality risk is an important facet of aging, conceptualizing human aging as the changes that occur in late life may be more fruitful than considering the risk of dying, per se. More specifically, many theorists have focused on aging as a series of declines.

Aging as Declines

Most colleges and universities offer courses with the title Adult Development and Aging, suggesting that the two topics are distinct; the implication is that aging is the opposite of development, and by definition, aging is decline. Yet the distinctions between development and decline are not clear-cut. For example, in infancy, synaptic pruning begins at birth. Nevertheless, we conceptualize changes to the brain in the first year of life as “development.” Aging decline, or senescence, suggests a process of deterioration, or the loss of capacity for growth.

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