THE RELIABILITY OF UPPER-LIMB ANTHROPOMETRY IN OLDER CHINESE PEOPLE

OBJECTIVE: To evaluate the validity of the Durnin-Womersley equations and to derive our local predictive equations for body fat from upper l imb skinfold thicknesses in older Chinese people in Hong Kong. To eval uate the validity of of mid-arm circumference and corrected arm muscle area in predicting lean tissue mass in the same population. DESIGN: C omparison of fat percentages predicted by Durnin-Womersley (D-W) equat ions with those estimated by Dual energy X ray absorptiometry (DXA). P redictive equations derived from regression between upper limb skinfol d thicknesses and Sat percentages estimated by DXA were similarly eval uated in internal and external validation groups. Mid-arm circumferenc e (MAC) and corrected arm muscle area (CAMA) were correlated with the limb lean tissue mass, body lean tissue mass and fat percentage. SUBJE CTS: 354, female and 263 male, apparently well, community dwelling sub jects, aged 69-82; of which 40 subjects of each sex were randomly sele cted from the study population for internal validation of the local pr edictive equations; 60 female and 33 male hospital medical outpatients , aged 61-87 y, were recruited for external validation. MEASUREMENTS: Triceps and biceps skinfold thicknesses, mid-arm circumference, body m ass index, fat percentages, limb and whole body lean tissue masses est imated by Hologic QDR-2000 bone densitometer. RESULTS: Fat percentages calculated by D-W equations were significantly different from those e stimated by DXA (average difference -2.4 (s.d. 4.8)% and +2.1 (5.2)% i n females and males respectively). The corresponding differences for o ur local predictive equations were not significant (-0.9 (4.7)% and -0 .5 (5.0)% in females and males respectively). There was a trend of und er-estimation of body fat with increasing fatness. in the hospital med ical outpatients there was a significant difference between fat percen tages predicted by our equation and those by DXA in female (-2.9(5.3)% ), bur nor in male (+0.3(4.3%) subjects. In males, MAC correlated with limb and body lean tissue masses as well as with fat percentage (r = 0.60, 0.68, 0.65 respectively). CAMA correlated similarly well with le an tissue masses but was more independent of fat percentage (r = 0.61, 0.65, 0.44 respectively), In females, both MAC and CAMA correlated po orly with limb and body lean tissue masses. Moreover, MAC correlated w ell with fat percentage (r = 0.80). CONCLUSIONS: Upper limb skinfold t hicknesses measurement is a valid means of predicting body fat in olde r Chinese people. Local predictive equations were more reliable that D -W equations, They were, however, subject to errors at the extreme end s of body fatness and in the presence of disease. in older females, MA C and CAMA were not reliable in predicting lean tissue mass, but MAC c ould be used to predict fat percentages. In older males, CAMA was more reliable than MAC in predicting lean tissue mass.