Build muscle and you'll live longer
New
UCLA research suggests that the more muscle mass older Americans have, the less
likely they are to die prematurely. The findings add to the growing evidence
that overall body composition -- and not the widely used body mass index, or
BMI -- is a better predictor of all-cause mortality.
The
study, published in the American Journal of Medicine, is the
culmination of previous UCLA research led by Dr. Preethi Srikanthan, an
assistant clinical professor in the endocrinology division at the David Geffen
School of Medicine at UCLA, that found that building muscle mass is important
in decreasing metabolic risk.
The
researchers analyzed data collected by the National Health and Nutrition
Examination Survey (NHANES) III, conducted between 1988 and 1994. They focused
on a group of 3,659 individuals that included men who were 55 or older and
women who were 65 or older at the time of the survey. The authors then
determined how many of those individuals had died from natural causes based on
a follow-up survey done in 2004.
The
body composition of the study subjects was measured using bioelectrical
impedance, which involves running an electrical current through the body.
Muscle allows the current to pass more easily than fat does, due to muscle's
water content. In this way, the researchers could determine a muscle mass index
-- the amount of muscle relative to height -- similar to a body mass index.
They looked at how this muscle mass index was related to the risk of death.
They found that all-cause mortality was significantly lower in the fourth
quartile of muscle mass index compared with the first quartile.
"In
other words, the greater your muscle mass, the lower your risk of death,"
said Dr. Arun Karlamangla, an associate professor in the geriatrics division at
the Geffen School and the study's co-author. "Thus, rather than worrying
about weight or body mass index, we should be trying to maximize and maintain
muscle mass."
This
study does have some limitations. For instance, one cannot definitively
establish a cause-and-effect relationship between muscle mass and survival
using a cohort study such as NHANES III. "But we can say that muscle mass
seems to be an important predictor of risk of death," Srikanthan said.
In
addition, bioelectrical impedance is not the most advanced measurement
technique, though the NHANES III measurements were conducted in a very rigorous
fashion "and practically, this is the best situation possible in a study
of this size," she noted.
"Despite
these limitations, this study establishes the independent survival prediction
ability of muscle mass as measured by bioelectrical impedance in older adults,
using data from a large, nationally representative cohort," Srikanthan and
Karlamangla write, adding that BMI's association with mortality in older adults
has proven inconsistent.
"We conclude that measurement of muscle mass
relative to body height should be added to the toolbox of clinicians caring for
older adults. Future research should determine the type and duration of
exercise interventions that improve muscle mass and potentially increase
survival in (healthy), older adults."
Story Source:
The
above story is based on materials provided by University of California - Los
Angeles Health Sciences. Note: Materials may be edited
for content and length.
Journal Reference:
1.
Preethi Srikanthan,
Arun S. Karlamangla. Muscle Mass Index as a Predictor of Longevity in
Older-Adults. The American Journal of Medicine, 2014; DOI:10.1016/j.amjmed.2014.02.007
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University of California - Los Angeles Health Sciences.
"Older adults: Build muscle and you'll live longer." Science Daily, 14 March 2014.
<www.sciencedaily.com/releases/2014/03/140314095102.htm>.