11.2 Introduction Life Expectancy Sensory Abilities

 Is old age to be feared? Or is it the most delightful time of life? What is it like to grow old?  Take the following true/false quiz: 1. Older people become more susceptible to short-term illnesses. 2. During old age many of the brain’s neurons die. 3. If they live to be 90 or older, most elderly people eventually become senile. 4. Recognition memory- the ability to identify things previously experienced- declines with age. 5. Life satisfaction peaks in the fifties and then gradually declines after 65.  All of the above statements are false. They are among the misconceptions about aging.

 The elderly are becoming a bigger population segment due to increasing life expectancy combined with decreasing birthrates.  Life expectancy at birth increased from 49 years in 1950 to 67 in  By 2050, about 35% of Europe’s population will be over the age of 60.  Life expectancy differs for males and females. Males are more prone to dying. The sex ratio is 105 males for every 100 females at birth.  Male infants’ death rates exceed females’ by one fourth during the first year.  Women outlive men by 4 years worldwide and by 5 to 6 years in Canada, the U.S., and Australia. At age 100, females outnumber males 5 to 1.

 Even if no one died before age 50 and all external illnesses were eliminated, average life expectancy would increase only to about 85 or a few years beyond. The body ages, becomes frail, stops cell reproduction, and becomes vulnerable to tiny insults.  Evolutionary biologists theorize that the reason we eventually wear out is due to our survival as a species: We pass on our genes most successfully when we raise our young and then stop consuming resources.  Once we’ve fulfilled our gene-reproducing task, there are no natural selection pressures against genes that cause degeneration in later life.

 Physical decline begins in early adulthood, but we are not usually acutely aware of it until later life.  Visual sharpness diminishes, and adaptation to changes in light level slows.  Muscle strength, reaction time, stamina, hearing, distance perception, and the sense of smell also diminishes.  With age, the eye’s pupil shrinks and its lens becomes less transparent, reducing the amount of light reaching the retina.  A 65-year-old receives only about one-third as much light as its 20-year-old counterpart. Thus, the 65-year-old needs three times as much light when reading or driving.