Estimation of lean body weight in older community-dwelling men

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT? * Lean mass decreases with age while total body fat increases, leading to changes in the pharmacokinetics and pharmacodynamics of drugs. * Dual-energy X-ray absorptiometry (DXA) is a useful reference method to measure lean body weight but may not be readily utilized clinically. * Limited methods for measurement of lean body weight using easily obtainable participant characteristics, such as height and weight, have been validated for use in people aged > or =65 years. WHAT THIS STUDY ADDS * This study has shown that lean body weight can be estimated using three different equations from easily obtainable participant characteristics with results comparable to DXA-derived estimates. * These equations may be useful tools to estimate lean body weight in situations where DXA is not practical. AIMS Lean body weight (LBW) decreases with age while total body fat increases, altering drug pharmacokinetics. The aim of this study was to evaluate the ability of the LBW equation to predict dual-energy X-ray absorptiometry (DXA)-derived fat free mass (FFM(DXA)) in older community-dwelling males compared with that of two existing FFM equations: the Heitmann and Deurenberg equations. METHODS Data were obtained from 1655 older men enrolled in the Concord Health and Ageing in Men Project. The predictive performance of the LBW and FFM equations to predict FFM(DXA) accurately was assessed graphically using Bland-Altman plots and quantitatively for precision and bias using the method of Sheiner and Beal in all participants and in frailty and body mass index (BMI) subgroups. RESULTS The LBW and Heitmann equations consistently overestimated FFM(DXA) for all frailty and BMI subgroups with a mean difference [95% confidence interval (CI)] of 5.5 kg (-0.65, 11.63 kg) and 3.34 kg (-2.84, 9.64 kg), respectively. The Deurenberg equation overestimated FFM(DXA) for overweight participants but underestimated FFM(DXA) for not-frail participants, with a mean difference (95% CI) of 1 kg (-7.23, 5.25 kg) for all participants. CONCLUSION LBW and FFM estimated using these equations give results comparable to DXA-derived FFM. The LBW and Heitmann equations provide a more consistent estimate of FFM(DXA) in all frailty and BMI groups despite the Deurenberg equation having the smallest mean difference. Further studies to determine whether the LBW equation is a clinically useful substitute for weight when determining drug dose in older people appear warranted.