The
Aging Body
By Colin
Milner
Chronic diseases
and disabilities were once thought inseparable from old
age. This view is changing rapidly as one disease after
another joins the ranks of those that can be prevented,
or at least controlled, through changes in lifestyle.
We now know, for example, that most people can avoid lung
disease by not smoking. As well, heart disease and stroke
rates have fallen at the same time that Americans have lowered
their fat consumption, begun to exercise more and quit smoking.
So, if chronic disease is not intrinsic to the aging process,
as many gerontologists now believe, then what is? Are there
universal or normal aging processes?
What is normal aging?
Today, gerontologists are discovering that age in years
doesn’t necessarily correlate with physiological age.
In fact, normal physiological aging is quite variable, according
to investigators involved in the Baltimore Longitudinal
Study of Aging (a long-term National Institute on Aging
(NIA) study begun in 1958 that has tracked the lives of
more than 1,000 people from age 20 to 90 and beyond).
Not only do individuals age overall at vastly different
rates, it is quite likely that age-related changes in various
cells, tissues and organs differ as well. For instance,
kidney function may decline more rapidly in some individuals.
In others, bone strength may diminish faster. The organs
that age fastest in one person may not age as rapidly in
another. This suggests that genes, lifestyle and disease
can all affect the rate of aging, and that several distinct
processes are involved.
Even within one person, organs and organ systems show different
rates of decline. However, some generalities can be made,
based on data from the NIA study. In the article we look
at three of these areas: the heart, body fat and muscle.
Heart
Heart muscle thickens with age. Maximal oxygen consumption
during exercise declines in men by about 10 percent with
each decade of adult life and in women by about 7.5 percent.
This decline occurs because the heart’s maximum pumping
rate and the body’s ability to extract oxygen from
blood both diminish with age.
Cardiovascular capacity predicts longevity better than risk
factors such as obesity, heart disease and smoking, according
to a study published in the New England Journal of Medicine
in 2002. A research team led by Dr. Jonathan Myers, of Veterans
Affairs Palo Alto Health System in California, concludes
that: “peak exercise capacity measured in metabolic
equivalents (MET) [is] the strongest predictor of the risk
of death among both normal subjects and those with cardiovascular
disease” after adjusting for age. Furthermore, a landmark
Texan study shows aerobic exercise can improve cardiovascular
fitness dramatically, even after three decades of inactivity.
Published in Circulation in 2001, the research outlines
how six months of endurance training led to a 100 percent
reversal of age-related declines in aerobic power in midlife
men.
Body fat
Typically, body fat gradually increases in adulthood until
individuals reach middle age. Then, it usually stabilizes
until late life, when body weight tends to decline. As weight
falls, older individuals tend to lose both muscle and body
fat. With age, fat is redistributed in the body, shifting
from just beneath the skin to deeper organs.
Women typically have a higher percentage of body fat than
men. However, because of differences in how this fat is
distributed – on the hips and thighs in women and
on the abdomen in men – women may be less susceptible
to certain conditions, including heart disease.
In fact, obesity levels among individuals ages 50 or older
have more than doubled in the last two decades, according
to AARP, a non-profit membership organization that serves
older adults.
“Morbidity from obesity may be as great as from poverty,
smoking or problem drinking,” states a June 2002 report
by the U.S. Department of Health and Human Services (HHS).
“Overweight and obesity are associated with an increased
risk for developing various medical conditions including
cardiovascular disease, certain cancers (endometrial, colon,
postmenopausal breast, kidney and esophageal), high blood
pressure, arthritis-related disabilities and type 2 diabetes,”
continues the report, Physical Activity Fundamental to Preventing
Disease. Regular physical activity and a nutritious diet
are essential to help older adults maintain a healthy weight
and reduce their health risks.
Muscles
Without exercise, estimated muscle mass declines 22 percent
for women and 23percent for men between the ages of 30 and
70. To this loss, add strength declines of 50 percent and
power reductions of 75 percent, and it’s easy to understand
how many older people lose their functional independence.
Exercise can slow the rate of loss of muscle mass, strength
and power.
The seminal paper on strength training and aging was published
in the Journal of the American Medical Association in 1990.
Maria Fiatarone, Bill Evans and other researchers from Tufts
University in Boston studied frail adults, average age 90,
who participated in eight weeks of high-resistance weight
training. The nine individuals who completed the study averaged
muscle strength gains of 174 percent and mid-thigh muscle
size increases of nine percent. Mean tandem gait speed also
improved by 48 percent. In 1994, Fiatarone, Evans and colleagues
published a landmark study in the New England Journal of
Medicine about the effects of strength training on frail
older adults. Of the 100 nursing home residents aged 72
to 98 years-old who participated in the study, 94 completed
the high-intensity strength training program. In just 10
weeks, these frail individuals saw increases in muscle strength
of 113 percent and cross-sectional thigh muscle of 2.7 percent.
The researchers also noted significant improvements in gait
velocity and stairclimbing power.
Once older adults have increased their strength and muscle
mass, they can maintain this improvement with relatively
little effort. A study conducted by Scott Trappe and colleagues
from Ball State University in Indiana shows that these gains
can be preserved with one weekly training session involving
three sets of 10 repetitions at 80 percent of one rep. max.
Trappe et. al.’s research was published in 2002 in
the Journals of Gerontology Series A: Biological Sciences
and Medical Sciences.
Not aging, but disuse
“Much of what we think about aging is not aging, but
disuse,” says Dr. Walter Bortz of Stanford University
Medical School. To explain disuse, the past president of
the American Geriatrics Society uses the analogy of a leg
in a cast. Although the leg shrivels, weakens and looks
old, it doesn’t age. That “old looking, old-functioning
leg” will become vital and active again with exercise,
but it won’t become younger. According to Bortz, there
are only two proven ways for humans to “look and feel
younger” and reduce the risks of dying or age-associated
diseases: engaging in regular exercise and eating a healthy
diet.
Health and wellness professionals are essentially partners
with older adults who want to maintain a youthful vitality.
By learning more about the aging process, those who work
with older clients can provide programming that helps these
individuals enjoy a vibrant, independent and active lifestyle
for as long as possible.
Colin Milner is the CEO of the International Council
on Active Aging, the world’s largest senior fitness
association.
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