BACKGROUND Loss of skeletal muscle mass (SMM) increases the risk of frailty and, together with excess fat mass (FM), is a risk factor for cardio-metabolic disease. However, use of body composition measurements in nutritional surveillance and routine clinical practice is limited by the lack of reference data. Our aim was to produce age-specific and sex-specific reference values for SMM and FM in the White ethnic adult population in the UK. Secondary objectives were to examine the tracking over time using a subsample of the population with repeated measures of body composition and to assess the validity of these reference values in different ethnic subgroups. METHODS We used data from segmental bioelectrical impedance analysis (BIA) in 390 565 participants, aged 40-69 years, in the UK Biobank, and data from dual-energy X-ray absorptiometry from n = 905 participants to validate the BIA measurements. SMM was calculated as the sum of the predicted muscle mass from the limbs. The LMS method was used to produce percentile curves for the SMM index (SMMI = SMM/height2 ) and the FM index (FMI = FM/height2 ). We investigated the validity of the White ethnic reference values by plotting z-scores (99.7% confidence interval) from Black and Asian groups to check if their confidence interval included zero. Longitudinal trajectories were predicted based on the baseline z-scores and the correlation between repeated measurements at follow-up. RESULTS The percentile curves show that SMMI declines in men from the age of 40, whereas in women, SMMI is more stable and decreases only slightly among women in the higher percentiles. FMI increases with age in both men and women. Women have higher FMI and lower SMMI than men in all age groups. The validity of the White-based reference values for non-White ethnic groups is poor. Longitudinal trajectories in body composition in the subsample of participants with a follow-up assessment show regression towards the mean in both men and women, with some evidence of declining SMMI only among men. The predicted 90% limits for the expected 5 year trajectories of SMMI and FMI can be used to identify people with unusual trajectories and in clinical practice to identify and track individuals at risk of excessive loss of SMM. CONCLUSIONS These body composition reference values developed from BIA in a middle/older-aged healthy White ethnic population in the UK could be used as a simple assessment tool for nutritional surveillance and to identify individuals with low SMMI or high FMI who may be at increased risk of disease and/or frailty.

中文翻译：

---

通过生物电阻抗测量的390 565英国成年人的骨骼肌质量和脂肪质量参考值。

背景技术骨骼肌质量（SMM）的损失增加了脆弱的风险，并且与多余的脂肪质量（FM）一起是心血管疾病的危险因素。但是，由于缺乏参考数据，人体成分测量在营养监测和常规临床实践中的使用受到限制。我们的目标是为英国白人成人群体中的SMM和FM生成年龄和性别特定的参考值。次要目标是使用人口子样本和重复的身体成分测量来检查随时间推移的追踪情况，并评估这些参考值在不同种族亚组中的有效性。方法我们使用了英国生物库中390565名年龄在40-69岁之间的参与者的分段生物电阻抗分析（BIA）数据，来自n = 905名参与者的双能X射线吸收仪数据，以验证BIA测量。SMM计算为四肢预测肌肉质量的总和。LMS方法用于生成SMM指数（SMMI = SMM / height2）和FM指数（FMI = FM / height2）的百分曲线。我们通过绘制来自黑人和亚洲人群体的z得分（置信区间为99.7％）来调查白人种族参考值的有效性，以检查其置信区间是否为零。纵向轨迹是根据基线z分数和后续重复测量之间的相关性来预测的。结果百分位曲线显示，男性40岁以后SMMI下降，而女性中SMMI更稳定，而较高百分位的女性中SMMI仅略有下降。男性和女性的FMI都随着年龄的增长而增加。在所有年龄段中，女性的FMI均高于男性，而SMMI则较低。非白人族裔基于白人的参考值的有效性很差。在接受随访评估的参与者子样本中，身体成分的纵向轨迹显示，男性和女性均朝着均值回归，并且有一些证据表明仅男性SMMI下降。SMMI和FMI的预期5年轨迹的预测90％限制可用于识别轨迹异常的人，并在临床实践中可用来识别和跟踪SMM过度丧失风险的人。