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Chapter 16
People want to live long lives. People want to live healthy
lives. People want to live quality lives. Many people want to bear children.
These facts lead to higher mean longevities (MLs) and ongoing
attempts to increase maximum longevity (XL). (For a few people,
increasing their MLs and XLs even means preserving their dead bodies by
freezing with the hope of being revitalized in a future better time.) Chapter 1
described results in terms of past and projected births, birth rates, death
rates, mean longevities, and population trends. The trends focused on changes
in the population of elders.
Results from these facts can also be viewed as changes in survival
curves (Survival
Curves 1999-2100). A survival curve shows the percentages of an initial
population that are still alive as the age of the population increases.
Survival curves often begin with a population at birth and follow that
population through time. Survival curves can also be developed mathematically
for people at different ages.
For more Internet survival curves, search the Images
section of http://www.google.com/ for
survival curve.
In the year 1900, the birth rate and the number of births in
the U.S. were high, but many children died during the first year of life. Many
others died before reaching adulthood. For many who reached adulthood, life
still contained many risks. Risks were high because of inadequate public
health, crowded urban living, low economic status, limited education, dangerous
working conditions, and limited knowledge of techniques for preventing and
curing diseases. Death rates remained substantial at all ages. Therefore, the
percentage of the population born in 1900 continued to decline significantly as
the age of the population increased (Fig.
16.1a).
During the century following 1900, conditions that
contributed to high death rates at all ages improved. Infant mortality rates
plummeted, and death rates at all ages declined. By 1950, almost all children
survived their first year of life and childhood. This trend continued through
2000. Those that reached adulthood continued to have a much lower death rate.
Therefore, the survival curve for a population born in 2000 is more rectangular
in shape than is the survival curve for a population born in 1900. Mean
longevity at all ages increased (Fig.
16.1a).
For the most recent statistics, go to the U.S. Census Bureau
web page at https://www.census.gov/topics/population.html
US Census Bureau 2020 census information is at US Census Bureau Reports - 2020 and 2017 .
People making projections believe that many conditions
affecting ML will continue to improve, and ML will continue to increase. This
book contains many suggestions that can increase ML. If conditions improve, the
survival curves for future populations in the U.S. will be even more
rectangular (Fig.
16.1a). Major changes in immigration since 2000 are likely to
have significant effects on the number and percentages of elders in the US
population. The effects from the Coronavirus COVID-19 pandemic that began in
early 2020 are ongoing. The US Census Bureau is taking these changes into
consideration in making population projections.
For activities related to
determining life expectancy for an individual, go to https://www.biologyofhumanaging.com/activit.htm#Life
Expectancy: Assignment.
For graphs and statistics on life
expectancies in the US, go to https://www.biologyofhumanaging.com/plan22.htm#Graphs.
For recent data on life expectancies in the US, go to the NCHS Life Expectancy
web page (https://www.cdc.gov/nchs/fastats/life-expectancy.htm)
If ML increases as projected, the
total population will gain many more elders 65+, and they will make up a much
larger proportion of the total population (Table
1.1). If birth rates do not decline much, the size of the total population
will also increase because many more people would be living longer. Using
moderate estimates, the U.S. population will increase from 332 million in 2020
to 355 million in 2030, 374 million in 2040, and 389 million in 2050. Using the
2020 population as the reference value, these increases are 7 percent, 12
percent, and 17 percent respectively for the total population. For elders 65+,
the corresponding values will be increases of 30 percent, 44 percent, and 53
percent respectively (Table
1.1). If conditions do not improve from those in 2020, mean longevities
will not increase, but the numbers of elders and the total population will
still increase because of continued births. (See Chapter 1 -
Population
Trends.)
What would happen if only conditions affecting mean
longevity were not changed but fundamental aging processes and age changes
could be slowed? Caloric restriction seems to slow age changes, resulting in
increases in maximum longevity (XL) for animals. If caloric restriction or some
other technique slowed human aging and people adopted that technique, the human
XL would increase. Most people would still die at the usual ages from the usual
causes of death. These causes are not age changes (e.g., atherosclerosis,
Alzheimer's disease, cancer). However, some people would survive longer than
ever before. The survival curve would become less rectangular at high ages (Fig.
16.1b). This change would add a small number of very old people to
the total population. Also, the percentage of elders in the total population
would increase slightly, and the total population would increase slightly.
What would happen if conditions improved AND aging processes
were slowed? Both ML and XL would increase. The survival curve would have
little change in shape, but it would become extended (Fig.
16.1c). The number of elders would increase; there would be many
elders who are very old; and elders would make up a larger proportion of the total
population. The total population would increase substantially. The total
population would become much larger than if only ML were increased.
Compare these different results in altering longevity using Fig.
16.1a, b, c.
If any of these three scenarios occurred globally, the same
trends in the total population on Earth would occur. In fact, the first
scenario has occurred. Historically, survival curves for humans have become
much more rectangular as MLs have increased. The human ML in prehistoric times
was probably under 20 years. The ML in the Roman empire at its peak was 23
years. By 1800, the ML in England was approaching 40 years. By 1900, the ML in
the U.S. was 47 years. Of course, MLs in less developed areas were probably
much lower and continue to be so. However, human MLs are increasing across the
globe. Elders are increasing in numbers and as a percentage of the total
population. The total human population is growing so rapidly that many people
speak of it as a population bomb that is exploding (Fig.
16.2). See also the Chapter 16 Supplementary
online figures.
These trends create complex and difficult challenges.
Present examples include providing adequate living accommodations, health care,
income, and quality of life for elders. These challenges will likely grow in
size and in complexity because aging and age-related changes in diverse realms
interact (e.g., biological, social, psychological, economic, spiritual).
Moreover, the challenges related to elders amplify challenges for society as a
whole. As more elders live longer with less disability and disease, they not
only increase problems and challenge, they also can have a larger role in
solving and meeting them.
Problems and challenges create needs and opportunities. Here
are a few problems and challenges that are creating needs and opportunities
related to aging.
To deal with the growing population of elders, people must
be better educated about all aspects of aging (e.g., biological, social,
psychological, economic, spiritual). Gerontology research and gerontology
education must expand and become more multidisciplinary and interdisciplinary.
They must become more multicultural, cross cultural, and international.
People who help formulate economic and public policy must be
more creative and productive to accommodate present and future changes in
demographics. The elders of the future are already here.
People seeking careers should consider the burgeoning
opportunities brought about by the enlarging elder population. Of course, a
background in gerontology can be invaluable. Almost any career path can be
modified to take advantage of and serve the special concerns, needs, and
desires of elders. Beyond health care,
diverse examples include architecture, art, community and regional planning,
education, law, marketing, management, recreation and leisure activities, and
creating ways by which elders can be contributors to society.
Finally, people must take more responsibility for protecting
the environment as the global population expands rapidly. A desirable human
civilization and quality of life cannot exist without a healthy ecosystem.
For information and discussions concerning potential
benefits and drawbacks from altering life expectancies, go to Controlling Aging:
What Would/Could/Should happen?
For a debate about altering life expectancies, go to Extending
Life Span .
Now you know. Where will you go from here?
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Copyright 2020: Augustine G. DiGiovanna, Ph.D.,
Salisbury University, Maryland
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