Associations of Lipid Levels and the Risk of Sarcopenic Obesity in Middle-aged and Elderly Chinese：a Cohort Study postprint

Abstract: Background　With the aging of the population，the incidence and impact of geriatric syndromes have received widespread attention，and sarcopenic obesity（SO），as one of these syndromes，has become a hot topic in recent studies. Studies have shown that lipid levels may be an important factor influencing SO，but studies on the correlation between lipid composition and SO have not yet reached consistent conclusions. Objective　To explore the relationship between blood lipid levels and the risk of SO in Chinese middle-aged and elderly people. Methods　Based on the 2011-2015 data of the China Health and Retirement Longitudinal Survey（CHARLS），the cohort study included middle-aged and elderly people with no SO at baseline in 2011. The study included middle-aged and elderly people without SO at baseline in 2011. Exposure factors were baseline total cholesterol（TC），triacylglycerol（TG），high-density lipoprotein cholesterol（HDL-C），and low-density lipoprotein cholesterol（LDL-C）in the study population，and the outcome event was the occurrence of SO in 2013 or 2015. SO was defined by combining the dual criteria of sarcopenia and obesity. Appendicular skeletal muscle mass adjusted by weight（ASM/W）was used to determine sarcopenia，and obesity was defined as a BMI ≥ 25 kg/m2 .COX proportional risk regression models were constructed to analyse the relationship between baseline TC，TG，HDL-C，LDL-C and the risk of SO，and possible non-linear associations were examined using a restricted cubic spline model. Results　A total of 5 268 study subjects were included，with a median age of 58（52，64）years and a cumulative follow-up of 20 592 person-years. There were 382 new cases of SO，with a cumulative incidence rate of 7.25%，of which the incidence rate of SO was 5.22%（128/2 451）in men and 9.02%（254/2 817）in women. The results of the fully adjusted proportional risk regression models for COX showed that，compared with the lowest quartile Q1 group of TC，the risk of SO was significantly higher in middle-aged and elderly people in the Q4（HR=1.35，95%CI=1.00 to 1.82）group（P<0.05）；compared with the Q1 group of TG，the risk of SO was significantly higher in the Q2（HR=1.55，95%CI=1.08 to 2.21），Q3（HR=2.07，95%CI=1.48 to 2.90），and Q4（HR=2.53，95%CI=1.82 to 3.52）groups（P<0.05）；compared with the Q1 group of LDL-C，the risk of SO was also significantly higher in the Q2（HR=1.38，95%CI=1.02 to 1.88），and Q4（HR=1.44，95%CI=1.07 to 1.95）groups；while the risk of SO was significantly lower in the Q2（HR=0.75，95%CI=0.58 to 0.96），Q3（HR=0.54，95%CI=0.41 to 0.71），and Q4（HR=0.43，95%CI=0.31 to 0.58）groups（P<0.05），as compared with the Q1 group of HDL-C. Restricted cubic spline model showed an inverse ‘L’-shaped association between TG level and the risk of SO（PNonliner<0.001），while TC（PNonliner=0.731），HDL-C（PNonliner=0.600），and LDL-C（PNonliner=0.400）were linearly associated with the risk of SO. Conclusion　TG，TC and LDL-C were the risk factors for SO in Chinese middle-aged and elderly people，while HDL-C had a protective effect，among which TG level had an inverted ‘L’ type association with SO. Therefore，lipid management may be important for the prevention and treatment of SO in Chinese middle-aged and elderly people.