|
E-mail this page to a friend!
Aging News & Information
Senior Citizens Experience Rapid Muscle
Deterioration with Extended Bed Rest
Cause attributed to decrease in muscle cells
ability to make protein
April 25, 2007 - Extended bed rest often
necessary during hospitalization leads to a substantial amount of
muscle deterioration in older adults, according to a new study. The
muscle loss for these senior citizens in the test was greater in 10 days
than for younger adults over a 28-day period in an earlier test.
The researchers attributed the increased muscle
tissue loss to inactivity that results in a large decrease in the
ability of muscle cells to make new protein, the primary constituent of
muscle.
Researchers at the University of Arkansas for
Medical Sciences (UAMS) report on the study in the April 25 issue of the
Journal of the American Medical Association.
The rate of muscle loss in 12 adults with an
average age of 67 over 10 days was more remarkable and in a shorter
period than a previous study of younger adults, said the research team
led by William J. Evans, Ph.D., director of the Nutrition, Metabolism
and Exercise Laboratory in the Donald W. Reynolds Institute on Aging at
UAMS.
Evans said the study, The Effect of 10 Days of Bed
Rest on Skeletal Muscle in Healthy Older Adults, demonstrated the best
case scenario, as the subjects were healthy with no functional
limitations.
Older patients hospitalized with disease or trauma
could also face other factors such as inflammation and decreased food
intake that could contribute to further loss of muscle tissue and
function, he said.
We found a dramatic reduction in muscle protein
synthesis brought on by inactivity that caused the muscle loss, said
Evans, the Jane and Ed Warmack Chair in Nutritional Longevity Nutrition,
Metabolism, a professor in the UAMS College of Medicine and a research
scientist for the Central Arkansas Veterans Healthcare System.
This is a striking loss of muscle in healthy
individuals. When you consider the chronically ill facing longer
hospitalizations or bed rest, the magnitude of muscle loss is
extraordinary and should be treated.
Evans said continued research by the team will
examine different strategies for preventing muscle loss. Those potential
treatments included nutritional supplements, exercise and the use of
insulin sensitizers to prevent the reduction in muscle protein
synthesis.
The 12 study participants, described as moderately
active prior to the study, remained in bed continuously for 10 days.
During that time, they consumed a diet with the recommended daily
allowance of protein (0.8 g/kg per day).
Measurements taken before and after bed rest
included the muscle protein synthesis rate over the course of 24 hours,
lean body mass, urinalysis and a leg-strength test. Evans said the
protein synthesis rate drives the increase or reduction in muscle mass,
as protein in muscle cells is always being created or broken down. When
the rate decreases, more protein is being broken down than created,
causing muscle loss.
According to the study, there was a 30 percent
decrease in the rate of protein synthesis in muscle cells between the
measurements taken before and after the 10 days of bed rest.
Evans said the researchers also found the bed rest
likely caused an increase in insulin resistance, which, he said, further
ratcheted down the protein synthesis rate.
Muscle mass was measured as a change in lean body
mass. The study reported an average 1.5 kg reduction in whole body lean
mass and 0.95 kg loss in leg lean mass after bed rest.
Evans noted that the older adult participants in
the UAMS study experienced more muscle loss in 10 days than did younger
participants after 28 days as reported in a 2004 article in the Journal
of Clinical Endocrinology Metabolism. In that study, an average loss of
less than 0.4 kg in leg lean mass was reported after 28 days bed rest in
subjects with an average age of 38.
UAMS co-authors of the research letter also
included Patrick Kortebein, M.D., an assistant professor in the
Department of Physical Medicine and Rehabilitation; Arny Ferrando,
Ph.D., a professor in the Department of Geriatrics; Juan Lombeida, M.D.,
resident physician; and Robert Wolfe, Ph.D., a professor in the
Department of Geriatrics.
An expert in nutrition and exercise, Evans past
research has examined the relationship between exercise, nutrition and
aging. His studies have demonstrated the ability of older men and women
to improve strength, fitness and health through exercise, even into the
10th decade of life.
Evans also has served as an expert advisor to the
National Aeronautics and Space Administration (NASA) on a number of
committees, including the Life Sciences Advisory Subcommittee and the
Science Working Group, which designed the Human Research Facility aboard
the International Space Station.
Editor's Notes:
The muscle loss study appeared in a research letter
published in the journal and is available online at http://jama.ama-assn.org/.
The Journal of the American Medical Association, published continuously
since 1883, is the most widely circulated medical journal in the world.
UAMS is the states only comprehensive academic
health center, with five colleges, a graduate school, a medical center,
six centers of excellence and a statewide network of regional centers.
UAMS has about 2,430 students and 715 medical residents. It is one of
the states largest public employers with about 9,400 employees,
including nearly 1,000 physicians who provide medical care to patients
at UAMS, Arkansas Childrens Hospital, the VA Medical Center and UAMS
Area Health Education Centers throughout the state. UAMS and its
affiliates have an economic impact in Arkansas of $5 billion a year. For
more information, visit
http://www.uams.edu.
Click to More Senior News on the
Front Page
Copyright: SeniorJournal.com |
