For older adults, being overweight may be considered a protective factor
for major
mobility disability, a finding that is consistent with
previous studies.
“Our data suggest that the risk of major mobility disability as a
result of poor strength may be greater than that posed by having a normal or
obese body mass index [BMI]. However, an important consideration in evaluating
the consequences of
obesity on function is the nature of the physical task,”
the researchers wrote in their study, published in the Journal of
Gerontology Series A: Biological Sciences and Medical Sciences.
According to Anthony Marsh, PhD, associate professor of health and
exercise science at Wake Forest University in Winston-Salem, N.C., and
colleagues, muscle weakness and obesity are two significant threats to mobility
that adults aged 70 and older face.
Marsh and colleagues conducted a secondary analysis of the randomized
controlled trial Lifestyle Interventions and Independence for Elders Pilot
(LIFE-P). The goal was to evaluate how baseline strength and BMI predicted
incidence of major mobility disability and changes in gait speed across 18
months.
“Our data used baseline strength and BMI so we can’t comment
on changes in these variables over time. However, taken together with the body
of literature, I would say that maintaining muscle strength should be a
priority for older adults. Fortunately resistance training is an effective way
to achieve this goal,” he told O&P Business News.
The researchers examined the association of strength and BMI on event
rates in 406 participants using performance measure of major mobility
disability.
Participants were aged 70 to 89 years, sedentary and functionally
limited, who were able to complete a 400-m walk test in 15 minutes at baseline.
Marsh and colleagues randomized them to one of two cohorts: physical activity
or health education intervention.
All participants were reassessed for major mobility disability every 6
months for up to 1.5 years. Researchers evaluated baseline grip strength and
BMI and how they were related to participants’ loss in ability to walk;
participants who could not complete the walk test in 15 minutes or less were
classified as having a major mobility disability.
Results showed that lower grip strength was associated with an increased
risk for developing major mobility disability (P<0.01).
“The study highlighted the importance of muscle weakness, low BMI
and obesity as risk factors for major mobility disability in older
adults,” Marsh said. “Interestingly, being overweight may be
protective for major mobility disability, which is consistent with several
large epidemiologic studies that have also found overweight to be protective in
older persons.”
While baseline grip strength and BMI were significant predictors of
major mobility disability, grip strength exhibited a linear relationship with
major mobility disability, whereas the relationship between BMI and major
mobility disability was curvilinear, according to Marsh.
“I was surprised by the strength of the association between
strength and major mobility disability since our measure of strength was for
the upper body, which is a limitation we acknowledge in the study,” he
said. “However, grip strength is considerably easier to assess in the
clinic compared to lower extremity strength.” — by Tara Grassia
For more information:
Marsh AP. Muscle strength and BMI as predictors of major mobility
disability in the Lifestyle Interventions and Independence for Elders Pilot
(LIFE-P). J Gerontol A Biol Sci Med Sci. 2011;
doi:10.1093/Gerona/glr158.
Disclosure: Marsh has no relevant financial disclosures.
