[Association of body mass index and waist circumference with frailty among people aged 80 years and older in Chinese].

Objective: To examine the association of body mass index (BMI) and waist circumference (WC) with frailty among oldest-old adults in China. Methods: A total of 7 987 people aged 80 years and older (oldest-old) who participated in the Chinese Longitudinal Healthy Longevity Survey (CLHLS) in 2017-2018 were included. Information on demographic characteristics, behavior pattern, diet, activities of daily living, cognitive function, health status, disease condition were collected by questionnaire and physical examination. Generalized linear mixed model and restricted cubic splines (RCS) were used to analyze the association of BMI and WC with frailty. Results: The mean age of all participants was 91.7 years, and their mean BMI and WC were (21.3±3.5) kg/m2 and (82.9±10.5) cm, respectively. The proportion of male was 42.3% (3 377/7 987), and the proportion of people with frailty was 33.7% (2 664/7 987). After controlling confounding factors, compared with T2 (19.1-22.1 kg/m2) of BMI, the OR (95%CI) of the female T1 (<19.1 kg/m2) and T3 (≥22.2 kg/m2) group was 1.39 (1.17-1.65) and 1.27 (1.07-1.52), respectively. Compared with T2 (77-85 cm) of WC, the OR (95%CI) of female T1 (<77 cm) and T3 (≥86 cm) group was 1.20 (1.01-1.42) and 1.10 (0.93-1.31), respectively. The results of multiple linear regression model with restrictive cubic spline showed that there was a non-linear association of BMI and WC with frailty in female. Conclusion: There is a U-shaped association of BMI and WC with frailty in female participants.目的： 研究中国高龄老年人群体质指数（BMI）、腰围（WC）与虚弱的关联。 方法： 利用“中国老年健康影响因素跟踪调查”项目中2017—2018年的横断面数据，将7 987名80岁及以上老年人纳入研究。通过问卷调查和体格检查，收集调查对象的人口学特征、行为方式、膳食情况、日常活动能力、认知功能、自我健康状况、现患疾病情况等信息。采用广义线性混合效应模型和限制性立方样条分析高龄老人BMI、WC与虚弱的关联。 结果： 7 987名研究对象的年龄为（91.7±7.7）岁，BMI和WC分别为（21.3±3.5）kg/m2和（82.9±10.5）cm，男性3 377名（42.3%），有虚弱症状者2 664名（33.7%）。广义混合效应模型显示，调整混杂因素后，与BMI的T2（19.1~22.1 kg/m2）组相比，女性T1（<19.1 kg/m2）和T3（≥22.2 kg/m2）组OR（95%CI）值分别为1.39（1.17~1.65）和1.27（1.07~1.52）；与WC的T2（77~85 cm）组相比，女性T1（<77 cm）和T3（≥86 cm）组OR（95%CI）值为1.20（1.01~1.42）和1.10（0.93~1.31）。限制性立方样条拟合多重线性回归模型分析结果显示，女性BMI和WC与虚弱之间呈非线性关联。 结论： 我国女性高龄老年人群的BMI和WC与虚弱均呈U型关联。.