| Background:The cause of hypertension is complex and it is generally recognized that it's the result of the combination of genetic and environmental factors.In addition to genetic factors,the current recognized risk factors are high salt diet,overweight and obesity,lack of physical activity,smoking,excessive drinking,etc.Domestic and international epidemiological studies have shown that overweight and obesity are important risk factors for hypertension.Current indexes of overweight and obesity include waist circumference(WC),waist-to-hip ratio(WHtR),Waist-to-hip ratio(WHR)and body mass index(BMI).Obesity indexes often change and previous studies on the association between obesity and hypertension risk were mostly cross-sectional.A few cohort studies focused on the baseline level regardless of the dynamic changes and the incidence of hypertension was often regarded as the outcome variable,so these studies had some limitations.Objective:The purpose of the study is to examine the association of baseline WC,WHtR,WHR,BMI and their changes with both blood pressure and the risk of hypertension among Chinese adults in 1997-2011.Methods:This study analyzes two waves of data from the China Health and Nutrition Survey collected in 1997 and 2011.The changes of blood pressure,WC,WHtR,WHR and BMI of the subjects from 1997 to 2011 were analyzed by sex stratification and two age groups 18-39y and 40-65y.The associations of WC,WHtR,WHR,BMI levels and their changes with blood pressure were analyzed using the multivarible linear regression models.The logistic regression model was used to analyze the associations of WC,WHtR,WHR,BMI levels and their changes as well as changes in abdominal obesity status with the risk of hypertension.Results:1.The levels of WC,WHtR,WHR,BMI and blood pressure increased in 14-year follow-up.The changes of WC,WHtR,WHR and BMI in the men aged 18-39 were greater than in the men aged 40-65(18-39 age group were 8.72cm,0.05,0.05,1.94kg/m2,40-65 age group were 5.11cm,0.03,0.03,0.89kg/m2 respectively),the changes of WC,WHtR and WHR were not significantly different in the two age groups in women,but the changes of BMI in the 18-39 age group was greater than that in the 40-65 age group(1.62kg/m2 vs.1.10kg/m2);The changes of SBP in the 40-65 age group were greater than the 18-39 age group in both gender(8.94mmHg vs.6.45mmHg in the men,11.21 mmHg vs.8.52 in the women),The changes of DBP in the 18-39 age group were greater than the 40-65 age group in men 4.78mmHg vs.3.02mmHg),but no significant difference was observed in the women;In the 18-39 age group,the changes of WC and BMI were greater in men,and in the 40-65 age group,the changes of WC,WHtR,WHR and SBP were greater in women;There was no significant difference in DBP in the two age groups.2.The correlation coeficient of WC and blood pressure changes in the 18-39 age group were greater than that in the 40-65 age group(?SBP and ?DBP were 0.27,0.11 and 0.20,0.19 in men,0.28,0.09 and 0.18,0.14 in women);?SBP>?DBP in the 18-39 age group;?baseline>?change.The correlation coefficient of WHtR and blood pressure changes in the 18-39 age group were greater than that in the 40-65 age group(?SBP and ?DBP were 5.01,2.45 and 3.41,3.37 in men,4.28,1.77 and 2.55,2.00 in women);?SBP>?DBP in the 18-39 age group,?DBP>?SBP in the 40-65 age group;?baseline>?change.The correlation coefficient of WHR and blood pressure changes in the 18-39 age group were greater than that in the 40-65 age group(?SBP and ?DBP were 2.75,0.19 and 1.96,0.03 in men,2.14,0.65 and 0.69,0.48 in women);?SBP>?DBP;?baseline>?change.The correlation coefficient of BMI and blood pressure changes in the 18-39 age group were less than that in the 40-65 age group(?SBP and ?DBP were 0.46,1.92 and 0.49,1.16 in men,0.55,1.41 and 0.37,0.48 in women);?baseline>?change in the 18-39 age group,?baseline>?change.in the 40-65 age group.3.The results of logistic regression showed that there was an increased tend on incidence of hypertension with increasing quartiles of WC change in the 18-39 age group(Ptrend<0.05).The risk of hypertension significantly increased at the fourth quartile(18-39 age group OR=2.56,95%CI:1.56-4.22,40-65 age group OR = 2.84,95%CI:1.77-4.57).There was an increased trend on incidence of hypertension with increasing quartiles of WHtR,WHR,BMI changes in both age groups.The risk of hypertension significantly increased at the fourth quartile(18-39 age group OR=2.51,95%CI:1.52-4.16;OR=3.05,95%CI:1.77-5.25;OR-3.28,95%CI:1.92-5.59;40-65 age group OR=2.89,95%CI:1.80-4.62;OR=1.93,95%CI:1.15-3.26;OR=3.26,5%CI:1.98-5.35).4.The men from normal to central obesity had greater increase in SBP and DBP than those who were still normal in the 18-39 age group(inceased value of SBP were10.0 and 4.0mmHg,increased value of DBP were 8.0 and 3.3mmHg,respectively),but there was no significant difference in the increased value of SBP and DBP in the 40-65 age group.The women from normal to central obesity had greater increase in SBP and DBP than those who were still normal in both age groups(increased value of SBP in the 18-39 age group were 6.2 and 11.OmmHg,and increased values of DBP were 4.0 and 7.0mmHg,respectively.The increased value of SBP in the 40-65 age group were 8.7 and 12.0mmHg,and the increased value of DBP were 2.0 and 5.3mmHg,respectively).The incidence of hypertension increased significantly among the subjects who changed from normal to central obesity between 1997 to 2011 with that still normal as a reference in the two age groups of both gender.Conclusions:From 1997 to 2011,there were positive correlations between the changes of WC,WHtR,WHR and the changes of SBP and DBP in Chinese adults aged 18 to 65.The associaton was significantly higher in 18-39 age group than in 40-65 age group and the association between the baseline level with blood pressure was greater than that of their changes;The associaton between the change of BMI with blood pressure was significantly higher in 40-65 age group than in 18-39 age group.The baseline levels of WC,WHtR,WHR,BMI and their changes were related to the incidence of hypertension;The increase of WC,WHtR,WHR,BMI and the change of central obesity status can increase the risk of hypertension.The results of this study suggest that,regardless of whether the baseline level is in the normal range,we should take the initiative to adopt a healthy lifestyle to control their growth and prevent the occurrence of hypertension. |
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