title: Ethnic-specific cut-points for sarcopenia: evidence from black South African women.
abstract: OBJECTIVE
  Age-related muscle and fat mass (FM) changes are ethnicity specific. We aimed to develop a cut-point for the muscle mass component of sarcopenia for black South African (SA) women, and to assess its predictive value, in comparison to established cut-points, to identify functional ability among older black SA women.
  
  
  METHODS
  In a cross-sectional study, a sarcopenia cut-point was calculated from dual energy X-ray absorptiometry (DXA)-derived appendicular skeletal muscle mass (ASM) indexes (ASMI) from two young black SA reference groups. The new cut-point was compared with the most recent Foundation for the National Institutes of Health (FNIH) criteria (ASM <15.02 kg; and ASM(BMI) <0.512), an internationally accepted cut-point (ASMI <5.5 kg/m(2)) and a residual method adjusting for FM. All cut-points were then applied to 221 older black women to predict gait speed and handgrip strength.
  
  
  RESULTS
  A cut-point of ASMI <4.94 kg/m(2) was derived from the young SA reference groups. Using this cut-point, 9.1% of older women were classified as sarcopenic, compared with 16.7-38.7% using other cut-points. The only cut-points that significantly predicted low functional ability (low gait speed and low handgrip strength) in older black women were the new SA cut-point and the FNIH ASM criterion. Multivariate logistic regression models for both these cut-points significantly predicted low handgrip strength (odds ratio (OR)=3.71, P=0.007 and OR=3.42, P=0.001, respectively) and low gait speed (OR=9.82, P=0.004 and OR=8.71, P=0.008, respectively).
  
  
  CONCLUSIONS
  The new SA cut-point had similar or greater odds of predicting reduced functional ability in older SA women when compared with other internationally accepted cut-points.
authors.affiliation: Centre of Excellence for Nutrition, North-West University, Potchefstroom, South Africa.
authors.forename: H S
authors.initials: HS
authors.lastname: Kruger
authors.affiliation: Faculty of Health Sciences, MRC/WITS Developmental Pathways for Health Research Unit, Department of Paediatrics, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: L K
authors.initials: LK
authors.lastname: Micklesfield
authors.affiliation: 1] Centre of Excellence for Nutrition, North-West University, Potchefstroom, South Africa [2] University of the Sunshine Coast, Maroochydore DC, Queensland, Australia.
authors.forename: H H
authors.initials: HH
authors.lastname: Wright
authors.affiliation: Centre of Excellence for Nutrition, North-West University, Potchefstroom, South Africa.
authors.forename: L
authors.initials: L
authors.lastname: Havemann-Nel
authors.affiliation: 1] Non-communicable Disease Research Unit, South African Medical Research Council, Tygerberg, South Africa [2] UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, Cape Town, 8000 South Africa.
authors.forename: J H
authors.initials: JH
authors.lastname: Goedecke
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D003906:Developing Countries; D005260:Female; D005684:Gait; D018737:Hand Strength; D006801:Humans; D008875:Middle Aged; D024510:Muscle Development; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging*; D010388:Pelvis; D017410:Practice Guidelines as Topic; D015995:Prevalence; D055948:Sarcopenia / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000208:ethnology / Q000503:physiopathology; D012680:Sensitivity and Specificity; D013019:South Africa / Q000453:epidemiology; D055815:Young Adult