Development and validation of a short portable sarcopenia measure in the African American health project.
BACKGROUND
Poor muscle size and function (sarcopenia) have an important role in the age-associated disability process. However, no commonly accepted index of sarcopenia exists for use in epidemiological studies.


METHODS
A cohort of 998 community-dwelling African Americans 49-65 years' old at baseline was used to construct the short portable sarcopenia measure (SPSM). SPSM was conceptualized as a measure of sarcopenia that combines estimates of muscle quantity and function into a single scale, is based on component items that can be obtained easily in the field, represents muscle status at a single time point that can be used without sex-specific adjustments, and can be used to follow change in muscle status over time with each person as his or her own control. We used exploratory factor analysis (EFA) to identify a unidimensional scale based on timed chair rises, lean mass, and grip strength divided by height. We used these three items and their EFA factor weights to construct SPSM (mean 9.0, median 9, range 0 [worst] to 18 [best] at baseline). Construct validity of the new measure, over a period of 36 months was examined.


RESULTS
SPSM required 8.5 pounds of equipment and 12.4 minutes to complete. It showed good score distribution and convergent, discriminant, and predictive validity with measures of muscle function, body composition, physical performance, psychological factors, and functional limitation cross-sectionally and with muscle function and body composition longitudinally. Extensive sensitivity analyses confirmed SPSM's robustness.


CONCLUSIONS
SPSM is a brief, portable, and valid measure of sarcopenia for use in epidemiological research. Similar studies in other populations are needed.
Miller
Douglas K
DK
Center for Aging Research, Indiana University, Indianapolis, IN 46202, USA. dokmille@iupui.edu
Malmstrom
Theodore K
TK
Andresen
Elena M
EM
Miller
J Philip
JP
Herning
Margaret M
MM
Schootman
Mario
M
Wolinsky
Fredric D
FD
D001741:Black or African American / Q000706:statistics & numerical data*; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology; D015992:Body Mass Index; D015331:Cohort Studies; D017097:Electric Impedance; D005260:Female; D015577:Geriatric Assessment / Q000379:methods*; D018737:Hand Strength; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology; D018908:Muscle Weakness / Q000175:diagnosis* / Q000208:ethnology*; D009135:Muscular Diseases / Q000175:diagnosis / Q000208:ethnology; D011237:Predictive Value of Tests; D012016:Reference Values; D012307:Risk Factors; D012519:Sarcoplasmic Reticulum / Q000502:physiology*; D012680:Sensitivity and Specificity; D012737:Sex Factors