LE Magazine August 2003
Muscle mass
Prevalence of sarcopenia and
predictors of skeletal muscle mass in healthy, older men and
women.
BACKGROUND: Sarcopenia refers to the loss of skeletal
muscle mass with age. The objective of this study was to
determine the prevalence of sarcopenia in a population of
older, community-dwelling research volunteers. METHODS:
Appendicular skeletal muscle mass was measured by dual x-ray
absorptiometry in 195 women aged 64 to 93 years and 142 men
aged 64 to 92 years. We defined sarcopenia as appendicular
skeletal muscle mass/height(2) (square meters) less than two
standard deviations below the mean for young, healthy
reference populations. We used two different reference
populations and compared prevalence in our population to that
reported in previous studies. Body mass index (BMI) was
calculated and physical activity and performance were measured
with the Physical Activity Scale for the Elderly, the Short
Physical Performance Battery, and the Physical Performance
Test. We measured health-related quality of life by using the
SF-36 general health survey. Serum estrone, estradiol, sex
hormone-binding globulin, parathyroid hormone and 25-hydroxy
vitamin D were measured in all participants and bioavailable
testosterone was measured only in men. Leg press strength and
leg press power were determined in men. RESULTS: The
prevalence of sarcopenia in our cohort was 22.6% in women and
26.8% in men. A subgroup analysis of women and men 80 years or
older revealed prevalence rates of 31.0% and 52.9%,
respectively. In women, skeletal muscle mass correlated
significantly with BMI and levels of serum estrone, estradiol
and 25-hydroxy vitamin D; in men, it correlated significantly
with BMI, single leg stance time, leg press strength, leg
press power, SF-36 general health score, Physical Performance
Test total score, and bioavailable testosterone levels. With
the use of linear regression analysis, BMI was the only
predictor of appendicular skeletal muscle mass in women,
accounting for 47.9% of the variance (p <.05). In
men, BMI accounted for 50.1%, mean strength accounted for
10.3%, mean power accounted for 4.1%, and bioavailable
testosterone accounted for 2.6% of the variance in
appendicular skeletal muscle mass (p <.05).
CONCLUSIONS: Sarcopenia is common in adults over the age of 65
years and increases with age. BMI is a strong predictor of
skeletal muscle mass in women and men. Strength, power and
bioavailable testosterone are further contributors in men.
These data suggest that interventions to target nutrition,
strength training and testosterone replacement therapy should
be further investigated for their role in preventing muscle
loss with age.
J Gerontol A Biol Sci Med Sci 2002
Dec;57(12):M772-7
Epidemiology of sarcopenia among the
elderly in New Mexico.
Muscle mass decreases with age, leading to "sarcopenia," or
low relative muscle mass, in elderly people. Sarcopenia is
believed to be associated with metabolic, physiologic and
functional impairments and disability. Methods of estimating
the prevalence of sarcopenia and its associated risks in
elderly populations are lacking. Data from a population-based
survey of 883 elderly Hispanic and non-Hispanic white men and
women living in New Mexico (the New Mexico Elder Health
Survey, 1993 to 1995) were analyzed to develop a method for
estimating the prevalence of sarcopenia. An anthropometric
equation for predicting appendicular skeletal muscle mass was
developed from a random subsample (n = 199) of participants
and was extended to the total sample. Sarcopenia was defined
as appendicular skeletal muscle mass (kg)/height2 (m2) being
less than two standard deviations below the mean of a young
reference group. Prevalences increased from 13% to 24% in
persons under 70 years of age to >50% in persons over
80 years of age, and were slightly greater in Hispanics than
in non-Hispanic whites. Sarcopenia was significantly
associated with self-reported physical disability in both men
and women, independent of ethnicity, age, morbidity, obesity,
income and health behaviors. This study provides some of the
first estimates of the extent of the public health problem
posed by sarcopenia.
Am J Epidemiol 1998 Apr
15;147(8):755-63
Predictors of skeletal muscle mass in
elderly men and women.
BACKGROUND: Elderly men and women lose muscle mass and
strength with increasing age. Decreased physical activity,
hormones, malnutrition and chronic disease have been
identified as factors contributing to this loss. There are few
data, however, for their multivariate associations with muscle
mass and strength. This study analyzes these associations in a
cross-sectional sample of elderly people from the New Mexico
Aging Process Study. METHODS: Data collected in 1994 for 121
male and 180 female volunteers aged 65 to 97 years of age
enrolled in The New Mexico Aging Process Study were analyzed.
Body composition was measured using dual energy X-ray
absorptiometry; dietary intake from three day food records;
usual physical activity by questionnaire; health status from
annual physical examinations; and serum testosterone, estrone,
sex-hormone binding globulin (SHBG), and insulin-like growth
factor (IGF1) from radioimmunoassays of fasting blood samples.
Statistical analyses included partial correlation and stepwise
multiple regression. RESULTS: The muscle mass and strength
(adjusted for knee height) decreased with increasing age in
both sexes. The muscle mass was significantly associated with
serum free-testosterone, physical activity, cardiovascular
disease and IGF1 in the men. In the women, the muscle mass was
significantly associated with total fat mass and physical
activity. Age was not associated significantly with muscle
mass after controlling for these variables. Grip strength was
associated with age independent of muscle mass in both sexes.
Estrogen (endogenous and exogenous) was not associated with
muscle mass or strength in women. CONCLUSIONS: Age-related
loss of muscle mass and strength occurs in relatively healthy,
well-nourished elderly men and women and has a multifactorial
basis. Sex hormone status is an important factor in men but
not in women. Physical activity is an important predictor of
muscle mass in both sexes.
Mech Ageing Dev 1999 Mar
1;107(2):123-36
Exercise training guidelines for the
elderly.
The capacity of older men and women to adapt to increased
levels of physical activity is preserved, even in the most
elderly. Aerobic exercise results in improvements in
functional capacity and reduced risk of developing Type II
diabetes in the elderly. High-intensity resistance training
(above 60% of the one repetition maximum) has been
demonstrated to cause large increases in strength in the
elderly. In addition, resistance training result in
significant increases in muscle size in elderly men and women.
Resistance training has also been shown to significantly
increase energy requirements and insulin action of the
elderly. PURPOSE: We have recently demonstrated that
resistance training has a positive effect on multiple risk
factors for osteoporotic fracture in previously sedentary
postmenopausal women. METHODS: Because the sedentary lifestyle
of a long-term care facility may exacerbate losses of muscle
function, we have applied this same training program to frail,
institutionalized elderly men and women. RESULTS: In a
population of 100 nursing home residents, a randomly assigned
high-intensity strength-training program resulted in
significant gains in strength and functional status. In
addition, spontaneous activity, measured by activity monitors,
increased significantly in those participating in the exercise
program whereas there was no change in the sedentary control
group. Before the strength training intervention, the
relationship of whole body potassium and leg strength was seen
to be relatively weak (r2 = 0.29, P < 0.001),
indicating that in the very old, muscle mass is an important
but not the only determining factor of functional status.
CONCLUSIONS: Thus, exercise may minimize or reverse the
syndrome of physical frailty, which is so prevalent among the
most elderly. Because of their low functional status and high
incidence of chronic disease, there is no segment of the
population that can benefit more from exercise than the
elderly.
Med Sci Sports Exerc 1999
Jan;31(1):12-17
Creatine supplementation improves
muscular performance in older men.
PURPOSE: Creatine supplementation has been shown to enhance
muscle strength and power after only five to seven days in
young adults. Creatine supplementation could therefore benefit
older individuals because aging is associated with a decrease
in muscle strength and explosive power. METHODS: We examined
the effects of seven days of creatine supplementation in
normally active older men (59 to 72 year) by using a
double-blind, placebo-controlled design with repeated
measures. After a three-week familiarization period to
minimize learning effects, a battery of tests was completed on
three occasions separated by seven days (T1, T2, and T3).
After T1, subjects were matched and randomly assigned into
creatine (N = 10) and placebo (N = 8) groups. After T2,
subjects consumed supplements (0.3 g x kg(-1) x d(-1)) for
seven days until T3. All subjects were tested for maximal
dynamic strength (one-repetition maximum leg press and bench
press), maximal isometric strength (knee extension/flexion),
upper- and lower-body explosive power (6 x 10-s sprints on a
cycle ergometer), and lower-extremity functional ability
(timed sit-stand test and tandem gait test). Body composition
was assessed via hydrostatic weighing, and blood samples were
obtained to assess renal and hepatic responses and muscle
creatine concentrations. RESULTS: No significant increases in
any performance measures were observed from T1 to T2 with the
exception of isometric right-knee flexion in the placebo group
indicating stability in the testing protocols. Significant
group-by -time interactions indicated the responses from T2 to
T3 were significantly greater (P < or= 0.05) in the
creatine compared with the placebo group, respectively, for
body mass (1.86 and -1.01 kg), fat-free mass (2.22 and 0.00
kg), maximal dynamic strength (7 to 8 and 1% to 2%), maximal
isometric strength (9 to 15 and -6% to 1%), lower-body mean
power (11% and 0%) and lower-extremity functional capacity (6
to 9 and 1% to 2%). No adverse side effects were observed.
CONCLUSION: These data indicate that seven days of creatine
supplementation is effective at increasing several indices of
muscle performance, including functional tests in older men
without adverse side effects. Creatine supplementation may be
a useful therapeutic strategy for older adults to attenuate
loss in muscle strength and performance of functional living
tasks.
Med Sci Sports Exerc 2002
Mar;34(3):537-43
Continued on Page 2 of 3
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