Presentation on theme: "11.2 Introduction Life Expectancy Sensory Abilities."— Presentation transcript:
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 2004. 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.