中华流行病学杂志  2015, Vol. 36 Issue (7): 691-694   PDF    
http://dx.doi.org/10.3760/cma.j.issn.0254-6450.2015.07.006
中华医学会主办。
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文章信息

阳益德, 付连国, 王政和, 王烁, 孟祥坤, 马蕊, 马冬梅, 马军. 2014.
Yang Yide, Fu Lianguo, Wang Zhenghe, Wang Shuo, Meng Xiangkun, Ma Rui, Ma Dongmei, Ma Jun. 2014.
超重/肥胖成年人体脂与血压关联中血脂中介效应的分析
Mediating effect of blood lipids on correlation between body fat and blood pressure among overweight adults
中华流行病学杂志, 2015, 36(7): 691-694
Chinese Journal of Epidemiology, 2015, 36(7): 691-694
http://dx.doi.org/10.3760/cma.j.issn.0254-6450.2015.07.006

文章历史

投稿日期:2015-01-06
超重/肥胖成年人体脂与血压关联中血脂中介效应的分析
阳益德1, 付连国2, 王政和1, 王烁1, 孟祥坤1, 马蕊1, 马冬梅1, 马军1     
1. 100191 北京大学公共卫生学院 北京大学儿童青少年卫生研究所;
2. 蚌埠医学院预防医学系
摘要目的 探索超重/肥胖成年人体脂与血压关联中血脂的中介效应。方法 选取20~55岁超重/肥胖个体作为研究对象,测量其血压、血脂、体脂率指标,采用中介效应模型分析体脂率与血压关联中血脂的中介效应。结果 男性和女性体脂率与SBP、DBP均呈正相关(SBP: β值分别为0.208 3和0.188 4,DBP: β值分别为0.205 2和0.209 6,P值均<0.001)。男性体脂率与HDL-C水平呈负相关(β =-0.142 2,P<0.01),与LDL-C水平呈正相关(β =0.180 5,P<0.001);女性体脂率与TC、LDL-C水平均呈正相关(β值分别为0.172 1和0.233 5,P<0.001)。控制体脂率后,男女性TC、TG水平与DBP均呈正相关(男: β值分别为0.095 6和0.090 5,女: β值分别为0.117 6和0.083 1,P值均<0.05),且女性TG水平与SBP呈正相关(β =0.127 2,P<0.001);女性体脂率与DBP的关联中,LDL-C水平具有中介效应(中介效应值为0.019 4,P<0.05),中介效应百分比为9.26%。结论 体脂率与血压呈正相关,男性体脂率与血压关联中血脂无中介效应,女性体脂率与血压关联中LDL-C水平具有中介效应。
关键词肥胖     血脂     体脂率     血压     中介效应    
Mediating effect of blood lipids on correlation between body fat and blood pressure among overweight adults
Yang Yide1, Fu Lianguo2, Wang Zhenghe1, Wang Shuo1, Meng Xiangkun1, Ma Rui1, Ma Dongmei1, Ma Jun1     
1 School of Public Health and Institute of Child and Adolescent Health, Peking University, Beijing 100191, China;
2 Department of Preventive Medicine, Bengbu Medical College
Abstract: Objective To understand the mediating effect of blood lipids on the correlation between body fat and blood pressure among overweight adults. Methods Overweight and obese subjects aged 20-55 years who had lived in Beijing for at least 1 year were recruited in this study, Body mass index (BMI) was used as a screening indicators. The percentage of body fat (PBF) was measured for the subjects by using dual energy X-ray absorptiometry(DXA). Mediating effect analysis was conducted to analyze the mediating effect of blood lipids on correlation between PBF and systolic blood pressure (SBP) as well as diastolic blood pressure (DBP). Results After adjusting for age, PBF was positively correlated with SBP and DBP in both males (β=0.208 3, β=0.205 2, P<0.001) and females (β=0.188 4, β=0.209 6, P<0.001). In male subgroup, PBF was negatively correlated with HDL-C level, but positively correlated with LDL-C level (β=-0.142 2, P<0.01 and β =0.180 5, P<0.001), while in female subgroup, PBF was positively correlated with both TC level and LDL-C level (β=0.172 1, P<0.001 and β =0.233 5, P<0.001). With PBF controlled, TC and TG levels were positively correlated with DBP in both males and females (β=0.095 6, 0.090 5 for males, β=0.117 6, 0.083 1 for females, P<0.05), and TG level was positively correlated with SBP in females (β=0.127 2, P<0.001). Further analysis indicated there was a significant mediating effect of LDL-C on correlation between PBF and DBP in females, with the mediating effect value of 0.019 4 (P<0.05). The ratio of mediating effect was 9.26%. Conclusion PBF was positively correlated with blood pressure, but blood lipids had no mediating effect on the correlation between PBF and blood pressure in males, while LDL-C level had mediating effect on PBF and blood pressure in females.
Key words: Obesity     Blood lipids     Percentage of body fat     Blood pressure     Mediating effect    

高血压是全球重大公共卫生问题[1, 2]。超重/肥胖与高血压密切相关[3, 4]。但目前肥胖导致高血压的内在机制尚不清楚,其发病可能与超重/肥胖导致代谢紊乱有关,如血脂异常、血糖异常及胰岛素抵抗等。体脂含量升高与血脂异常密切相关,血脂异常又与血压升高存在关联[5],其中血脂的中间效应鲜有研究。既往研究显示,超重/肥胖人群与正常体重人群相比,肥胖相关指标(如BMI)、血脂指标与血压关联更加密切[6, 7]。为此本文以超重/肥胖成年人为研究对象,探讨血脂在体脂与血压关联的中介效应。 对象与方法

1. 研究对象:以BMI作为筛选指标,于2014年4月1日至5月2日选取北京市本地居住1年以上的20~55岁超重/肥胖个体。通过询问病史,排除心、肺、肝、肾等重要脏器疾病和身体发育异常、残疾、畸形以及继发性肥胖等疾病。本研究通过北京大学医学部伦理委员会审批,调查前研究对象均签署知情同意书。

2. 调查内容与方法:采用问卷调查获得一般人口特征信息。体格检查按常规,其中身高以cm为单位(精确至0.1 cm),体重以kg为单位(精确至0.1 kg),并计算BMI,采用水银血压计测量SBP和DBP,重复测量2次取均值为最终血压[如2次测量差值超过10 mmHg(1 mmHg=0.133 kPa)需测量第3次,记录相近2次测量值]。本研究编制了规范的体检手册,检测人员均经过规范化培训,且考核合格后进行现场测量。根据中国肥胖问题工作组制定的标准筛查[8],超重:24≤BMI(kg/m2)<28,肥胖:BMI≥28 kg/m2。采用日本奥林巴斯株式会社全自动生化仪AU400、美国西门子试剂盒检测TC、TG、HDL-C和LDL-C。由专业医师采用双能X线吸收法(美国GE公司)测量体脂,利用标准模式扫描,X射线剂量为 0.4 LGy,支持电流为0.15 A,并计算体脂率(PBF)。

3. 统计学分析:采用SPSS 17.0软件,各指标性别间差异采用t检验。为使不同变量间中介效应具有可比性,将PBF、血压及血脂指标分性别进行标准化处理(原始值减去均值除以标准差)。根据Baron和Kenny[9]提出的中介效应理论,将血脂(TC、TG、HDL-C和LDL-C)作为中介变量(M),PBF为自变量(X),血压为因变量(Y)进行中介效应分析,即X对Y的总效应c可被分解为直接效应c′和间接效应ab,a为X对M的效应,b为控制X后,M对Y的效应(图 1)。采用SPSS程序进行中介效应分析[10],利用Sobel法检验中介效应。

注:X 为PBF,M 为血脂指标(TC/TG/LDL-C/HDL-C),Y 为血压指标(SBP/DBP)图 1 中介效应模型
结果

1. 一般人口学特征:本研究共选择1 322名数据完整的研究对象,其中男性521人(39.4%),女性801人(60.6%);平均年龄(37.16±9.12)岁,其中女性(38.21±9.37)岁,男性(35.53±8.48)岁,差异有统计学意义(P<0.001);PBF、HDL-C为女性均高于男性(P值均<0.05),SBP、DBP、TC、TG和LDL-C为男性均高于女性(P值均<0.05)。见表 1

表 1 研究对象的基本特征(x±s)

2. PBF、血脂及血压间的关联:男女性PBF均与SBP呈正相关(校正年龄后β值分别为0.208 3、0.188 4,P值均<0.001)。男性PBF与HDL-C呈负相关(校正年龄后β=-0.142 2,P<0.01),但与LDL-C呈正相关(β=0.180 5,P<0.001);女性PBF与TC、LDL-C呈正相关(校正年龄后β值分别为0.172 1、0.233 5,P值均<0.001);控制PBF后,男性血脂指标均与SBP无关联(校正年龄后P值均>0.05),女性仅TG与SBP关联(校正年龄后β=0.127 2,P<0.001)。见表 2

表 2 超重/肥胖人群PBF、血脂与SBP的关联

男女性PBF均与DBP呈正相关(校正年龄后β值分别为0.205 2、0.209 6,P值均<0.001);控制PBF后,男性TC、TG均与DBP呈正相关(校正年龄后β值分别为0.095 6、0.090 5,P值均<0.05),女性TG、LDL-C均与DBP呈正相关(校正年龄后β分别为0.117 6、0.083 1,P值均<0.05)。见表 3

表 3 超重/肥胖人群PBF、血脂与DBP的关联

3. LDL-C在女性超重/肥胖人群中PBF与DBP关联的中介效应:以上分析显示,男女性PBF、血脂及SBP三者的关联,男性PBF、血脂及DBP三者的关联均不满足c、a、b同时具有统计学意义的条件,故未进一步分析中介效应;女性PBF、LDL-C与DBP三者间c、a、b同时具有统计学意义,满足中介效应分析前提条件。中介效应分析发现,女性PBF与DBP的关联中,LDL-C具有中介效应(中介效应值为0.019 4,P<0.05),中介效应百分比为9.26%,PBF与DBP的直接效应为0.190 2(P<0.001)。见表 4

表 4 LDL-C在女性超重/肥胖人群中PBF与DBP关联的中介效应分析
讨论

目前肥胖与血压关联的内在机制尚不清楚[11, 12]。本研究通过双能X线吸收法测得PBF,分析其与血压关联,并探讨血脂指标在超重/肥胖者中对于PBF与血压关联的中介效应。采用双能X线吸收法测量全身脂肪含量计算PBF,结果准确可靠[13]。虽然研究采用方便抽样,但研究对象年龄分布相对均衡,不包含特殊行业人群(如运动员等),在一定意义上能够代表超重/肥胖人群,但样本中不含正常体重人群,是其局限性。

本研究校正年龄后发现,男性超重/肥胖人群中PBF与SBP/DBP密切相关(β值分别为0.208 3和0.205 2),而女性超重/肥胖人群中PBF与SBP或DBP相关(β值分别为0.188 4和0.209 6)。Hariri等[14]研究发现双能X线吸收法测得体脂含量与SBP偏相关系数为0.22,而其与DBP的偏相关系数为0.27。PBF与血脂指标的关联具有性别差异,如男性超重/肥胖者仅HDL-C和LDL-C与PBF有相关性(β值分别为-0.142 2和0.180 5),女性超重/肥胖者中仅TC和LDL-C与PBF相关(β值分别为0.172 1和 0.233 5),其相关方向与以往研究一致[14],说明超重/肥胖男性体脂增加可能主要导致HDL-C水平降低和LDL-C水平升高,而女性体脂增加主要导致TC和LDL-C水平升高。校正体脂含量后,进一步分析这些指标与血压的关系发现,在男性超重/肥胖者TC、TG与DBP相关,而女性则TG与SBP、LDL-C与DBP相关。

中介效应分析发现,仅LDL-C在女性超重/肥胖者的PBF与DBP关联中起中介作用(中介效应比例为9.26%),提示女性超重/肥胖者中体脂与血压存在内在关联。有研究发现LDL-C在动脉粥样硬化的发生、发展过程中起重要作用[15],可能是其导致血压升高的内在机制。提示超重/肥胖女性,如LDL-C水平出现异常,调整LDL-C水平即可能控制其血压,但男性超重/肥胖者却未发现类似中介效应。国外有研究发现成年男性血压与睾酮水平呈负相关,高血压者睾酮水平低于血压正常者[16]。但就目前而言,男性超重/肥胖者其PBF与血压的关联及女性超重/肥胖者LDL-C对于其体脂与血压关联的中介作用机制均有待进一步研究。

参考文献
[1] Kearney PM,Whelton M, Reynolds K, et al. Global burden of hypertension:analysis of worldwide data[J]. Lancet,2005,365(9455):217-223.
[2] Lawes CMM, Hoorn SV, Rodgers A. Global burden of blood- pressure-related disease,2001[J]. Lancet,2008,371(9623):1513-1518.
[3] Chandra A,Neeland IJ,Berry JD,et al. The relationship of body mass and fat distribution with incident hypertension:observations from the Dallas Heart Study[J]. J Am Coll Cardiol,2014,64(10):997-1002.
[4] Stamler R, Stamler J, Riedlinger WF,et al. Weight and blood pressure. Findings in hypertension screening of 1 million Americans[J]. JAMA,1978,240(15):1607-1610.
[5] Paradisi G, Smith L, Burtner C, et al. Dual energy X-ray absorptiometry assessment of fat mass distribution and its association with the insulin resistance syndrome[J]. Diabetes Care,1999,22(8):1310-1317.
[6] Liu L,Ikeda K,Chen M,et al. Obesity,emerging risk in China: trend of increasing prevalence of obesity and its association with hypertension and hypercholesterolaemia among the Chinese[J]. Clin Exp Pharmacol Physiol,2004,31 Suppl 2 :S8-10.
[7] Wang HW,Cao J,Li JX,et al. Blood pressure,body mass index and risk of cardiovascular disease in Chinese men and women[J]. BMC Public Health,2010,10:189.
[8] Working Group on Obesity in China (WGOC). Guideline for prevention and control of overweight and obesity in Chinese adults[J]. Acta Nutrimenta Sinica,2004,26(1):1-4. (in Chinese)中国肥胖问题工作组. 中国成人超重和肥胖症预防与控制指南(节录)[J]. 营养学报,2004,26(1):1-4.
[9] Baron RM,Kenny DA. The moderator-mediator variable distinction in social psychological research:conceptual,strategic,and statistical considerations[J]. J Pers Soc Psychol,1986,51(6):1173-1182.
[10] Preacher KJ,Hayes AF. SPSS and SAS procedures for estimating indirect effects in simple mediation models[J]. Behav Res Methods Instrum Comput,2004,36(4):717-731.
[11] Zhou ZQ,Hu DY,Chen J. Association between obesity indices and blood pressure or hypertension:which index is the best?[J]. Public Health Nutr,2009,12(8):1061-1071.
[12] Niu JJ,Seo DC. Central obesity and hypertension in Chinese adults:a 12-year longitudinal examination[J]. Prev Med,2014,62:113-118.
[13] Ritz P, Sallé A, Audran M,et al. Comparison of different methods to assess body composition of weight loss in obese and diabetic patients[J]. Diabetes Res Clin Pract,2007,77(3):405-411.
[14] Hariri AA,Oliver NS,Johnston DG,et al. Adiposity measurements by BMI,skinfolds and dual energy X-ray absorptiometry in relation to risk markers for cardiovascular disease and diabetes in adult males[J]. Dis Markers,2013,35(6):753-764.
[15] Badimon L,Vilahur G. LDL-cholesterol versus HDL-cholesterol in the atherosclerotic plaque:inflammatory resolution versus thrombotic chaos[J]. Ann New York Acad Sci,2012,1254:18-32.
[16] Guarner-Lans V, Rubio-Ruiz ME,Peréz-Torres I,et al. Relation of aging and sex hormones to metabolic syndrome and cardiovascular disease[J]. Exp Gerontol,2011,46(7):517-523.