Physical Development // 291
Have you ever thought about how
long you are likely to live? Might
you be able to live to be 100 years
old? Type in the following on your
Internet browser: The Living to Be
100 Life Expectancy Calculator. That
will give you access to Dr. Thomas
Perl’s website (www.livingtobe100.
com), where in only about 10
minutes you can answer questions
about different aspects of your life
that will provide a number indicating
how long you are likely to live. A
special beneﬁ t is that you also will
get feedback about how to improve
your number. Dr. Perl is currently
conducting one of the largest studies
of centenarians (those who live to
be100), and his life expectancy
calculator is based on research that
has been conducted on the factors
that predict longevity.
How i s y our c ur r en t
behavi or bui l di ng a f oundat i on
for a healthy late adulthood? I f
your f ut ur e s el f coul d t i me- t r avel
to visit you, would he or she say
“Thanks!”—or inst ead “What
wer e you t hi n ki n g? ”
thinner and grayer due to a lower replacement rate and a decline in melanin production.
Individuals lose height in middle age as a result of bone loss in the vertebrae, and many
gain weight (Onwudiwe & others, 2011). Once individuals reach their 40s, age-related
changes to their vision usually become apparent, especially dif culty in seeing things up
close. The sense of taste can also be affected by age, as taste buds (described in Chapter
3) are less likely to be replaced.
For women, entering middle age means that menopause will soon occur. Usually
in the late 40s or early 50s, a woman’s menstrual periods cease. With menopause comes
a dramatic drop in the ovaries’ production of estrogen. Estrogen decline produces
uncomfortable symptoms in some menopausal women, such as hot ashes (sudden,
brief ushing of the skin and a feeling of elevated body temperature), nausea, fatigue,
and rapid heartbeat. However, menopause overall is not the negative experience for
most women it was once thought to be (Henderson, 2011; Judd, Hickey, & Bryant,
With age, for both men and women, a variety of bodily systems are likely to
show the effects of wear and tear as the body becomes less and less able to repair
damage and regenerate itself (Lamoureux & others, 2010). Physical strength
declines and motor speed slows; bones may become more brittle (especially
for women). Nearly every bodily system changes with age. Signi cantly, how-
ever, even as age is associated with some inevitable decline, important aspects
of successful aging are within the person’s control. For instance, a healthy diet
and regular exercise can help to prevent or slow these effects. Regular physical
activity can have wide-reaching bene ts not only for physical health but for cogni-
tive functioning as well (Kraft, 2012; Snowden & others, 2011). A recent study of older
adults, for example, revealed that exercise increased the size of the hippocampus and
improved memory (Erickson & others, 2011).
O n e w a y o l d e r a d u l t s n a v i g a t e t h e p h y s i c a l c h a n g e s a s s o c i a t e d w i t h a g e i s t h r o u g h a
process of changing their goals and developing new ways to engage in desired activities.
Psychologists refer to this process as selective optimization with compensation, which
means that older adults match their goals with their current abilities and compensate for
declines by nding other ways to do the things they enjoy (Riediger & Freund, 2006).
A 75-year-old who can no longer drive because of cataracts might become an
expert on her city’s train and bus system, for example.
O n t h e i s l a n d o f O k i n a w a ( p a r t o f J a p a n ) , i n d i v i d u a l s l i v e l o n g e r t h a n
anywhere else in the world, and Okinawa has the world’s highest prevalence
of centenarians — p e o p l e w h o l i v e t o 1 0 0 y e a r s o r b e y o n d . E x a m i n a t i o n o f
Okinawans’ lives provides insights into their longevity. Speci c factors are
diet (they eat nutritious foods such as grains, sh, and vegetables); lifestyle
(they are easygoing and experience low stress); community (Okinawans
look out for one another and do not isolate or ignore older adults); activity
(they lead active lifestyles, and many older adults continue to work); and
spirituality (they nd a sense of purpose in spiritual matters) (Willcox &
others, 2008). Just as physical changes are interwoven with socioemotional
processes in childhood and adolescence, so they are as human beings enter
the later stages of life.
Biological Theories of Aging Of the many proposed biological the-
ories of aging, three especially merit attention: cellular-clock theory, free-
radical theory, and hormonal stress theory.
T h e cellular-clock theory i s L e o n a r d H a y ick’s (1977) view that cells
can divide a maximum of about 100 times and that, as we age, our cells
become less capable of dividing. Hay ick found that cells extracted from
adults in their 50s to 70s had divided fewer than 100 times. The total
number of cell divisions was roughly related to the individual’s age. Based
on the way cells divide, Hay ick places the upper limit of the human life
span at about 120 years.
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