Ten-Year Changes Of Obesity Among Chinese Adults And Its Attribution To All-cause Mortality

Background and ObjectivesHigh body mass index(BMI)was associated with 4.4 million deaths,according to the Global Burden of Disease Study 2013.Obesity as a disease is the key factor of a variety of chronic diseases;moreover,it is one of the world’s most concerned comprehensive social problems that lead to health inequities.The objectives of the present study were to analyze obesity prevalence,obesity inequality and change characteristics among different groups during 2002-2012 by using different obesity indicators,and to assess the relationship between obesity and mortality during 2002-2016.This study provides a theoretical basis for(1)the development of obesity prevention and control strategies,(2)the implementation of targeted obesity intervention programs,(3)the improvement of life expectancy and the promotion of health equity.MethodsA total of 141,141 and 119,694 people aged 18 and above were surveyed respectively by method of Multi-stage cluster random sampling based on the largest and most representative datasets of China Nutrition and Health Survey in 2002 and 2012.Questionnaires were designed to identify basic demographic characteristics,smoking and alcohol use;standard methods and uniform devices were used to measure body height,weight and waist circumference(WC)and calculate BMI and waist-to-height ratio(WHtR);venous blood test was conducted for serum triglycerides and other indicators.The Criteria of Weight for Adults,a health industry standard of the People’s Republic of China,was applied to determine general obesity(i.e.24 kg/m2<BMI≤28 kg/m2 for overweight,and BMI>28 kg/m2 for obesity)and central obesity(i.e.WC>90cm for males,and>85cm for females);and WHtR>0.50 was also considered as central obesity.Hypertriglyceridemic-waist(HTGW)phenotype was determined according to the US National Cholesterol Education Program-Adult Treatment Panel III(NCEP ATP III)Guidelines.The means and standard errors of body weight,WC and BMI of different subgroups were calculated;the prevalence of general obesity,central obesity,WHtR≥0.50 and HTGW and 95%confidence interval(CI),as well as absolute and relative changes from 2002 to 2012 were predicted.Prevalence ratio and relative index of inequality(RII)were also calculated to assess the inequality of obesity related to socioeconomic status.The dataset was analyzed by using stratum-specific weights from the standard population of 2009 Chinese census population.The statistical significance of the changes during 2002 to 2012 was tested by using the pooled t test.The baseline data was from Shanxi Province of 2002 China Nutrition and Health Survey.The death investigation and follow-up visit was carried out from December 2015 to March 2016.The visits covered up to 5,360 of 7,007 people recorded with complete core information,including age,gender,height,weight and WC,representing a follow-up rate of 76.5%.The participants of this study were divided into eight groups according to BMI,WC and WHtR,respectively.Taking the group with the lowest mortality density as the reference group,the Cox regression model was used to estimate relative risk and 95%CI of death by whole population,gender and age group(≥60 years;<60 years old)and then,adjusted by age,gender,smoking,alcohol use and education in the baseline.The sensitivity analysis was conducted by excluding smokers,unexpected deaths,those dead within the first year of follow-up and those follow-up less than three years.Two-sided p<0.05 was considered statistically significant.All analyses were performed using the SAS software,version 9.3(SAS Institute Inc.,Carey,NC,USA).Results1.From 2002 to 2012,the means of body weight,WC and BMI of male adults increased by 2.1 kg,2.7cm and 0.6 kg/m2,respectively,and those of female adults,by 1.1 kg,2.1cm and 0.3 kg/m2,respectively.The three indicators declined among urban men over 60 years old and urban women over 50 years old.Those indicators among rural residents increased more than three times of that of urban residents.WC exhibited the most noticeable increase and BMI the least.2.In 2012,the overweight and obesity rates reached 30.0%and 11.8%,respectively.The prevalence of central obesity,WHtR≥0.5 and HTGW rose to 25.7%,48.4%and 13.1%,respectively.The central obesity rate grew faster than general obesity rate.Obesity rate expanded faster in rural areas than in the urban areas.Obesity rate of people aged 18 to 49 years grew faster than that of people at other ages.The rate of general obesity remained basically stable among people over the age of 60 and dropped among urban female population.3.The means of weight,WC and BMI and rates of general obesity and central obesity among the male population increased with the levels of socioeconomic status(SES),which was opposite to that of the female population.The increase of obesity rate was most notable in population with low-educated,low-income and manual occupation.The inequality of obesity related to SES narrowed among the male population,but widened among the female population during 2002 and 2012.Women with low income and low education level were more vulnerable to obesity.4.The present study followed 94,606.4 person-years for 12.7 years on average,including 615 deaths.The mortality density was 650.0 per 100,000 person-years.With BMI range of 26.0-27.9 kg/m2 as a reference,the relative risk of death after multivariate adjustment increased in four groups(BMI<18.5,18.5-19.9,22.0-23.9 and>30.0 kg/m2)to 1.90(1.26-2.86),1.68(1.15-2.45),1.49(1.08-2.06)and 1.72(1.07-2.76),respectively.After the adjustment of multiple factors(BMI included),the relative risk of death reached 1.85(1.11-3.08)among male with WC ≥100 cm and female with WC>95 cm,which was higher than the reference groups(90 cm≤ Male<95 cm,85 cm≤Female<90 cm).The RR of death in WHtR groups was not statistically significant compared with the reference group(0.47-0.49).Low body weight(BMI<18.5 kg/m2)and high WC(male≥100 cm and female>95 cm)were more relevant in predicting death of adults aged 60 years and above,the RR of death were 1.94(1.20-3.15)and 2.07(1.08-3.96),respectively.ConclusionThe obesity rate continued to grow in China during 2002 and 2012.Significant differences in the epidemiological characteristics of different subgroups were observed.The prevention and control of obesity should emphasize on the rural population,especially rural male,and population in low socioeconomic status;in the meanwhile,attention should be paid to the increasing risk of death caused by low body weight malnutrition in the elderly.Central obesity rate grew remarkably in China.WC was an important predictor of death independent of BMI.WC and BMI should be jointly used as the simple rapid screening and predictive indicators of obesity and the risk of death.The present study suggested that keeping healthy body weight should be employed as an important public health strategy,in cooperation with implementing multidimensional interventions on obesity and its determinants,which could be useful in the prevention and control of chronic diseases,the reduction of premature death,and the promotion of health equity.