Prevalence and ethnic pattern of overweight and obesity among middle-aged and elderly adults in China

Overweight and obesity are associated with increased morbidity and mortality, and a pooled analysis from 16 prospective cohort studies showed that overweight is associated with double the risk of developing cardiometabolic multimorbidity and the risk increases to be more than four times in obese individuals.1 Another meta-analysis showed that obesity was associated significantly with higher all-cause mortality.2 In addition, a cohort study based on the large national registry in London also showed that obesity could increase the risk of sudden cardiac death such as sudden arrhythmic death syndrome, and the prevalence of critical and non-critical coronary artery disease was significantly higher in obese individuals (23% vs. 10% in non-obese individuals, P < 0.001).3 In China, rapid economic growth has led to changes in dietary and physical activity patterns,4 especially in the past two decades, which in turn have led to an increase in obesity and overweight prevalence.5 Fortunately, it is well established that appropriate control of obesity through lifestyle changes could result in a significant reduction in cardiovascular morbidity and mortality.6,7 Therefore, ongoing reliable estimations are necessary to plan effective national prevention for obesity management. Although a few studies were available to estimate the prevalence of obesity and overweight, the data from different studies were conducted in different areas or population.8–10 Only one study based on the China Health and Nutrition Surveys (CHNS) described the secular trends in general and abdominal obesity among Chinese adults from 1993 to 2009,5 and another two studies estimated the prevalence and trends of abdominal obesity.11, 12 A recent publication reported the prevalence of obesity and overweight in different ethnic groups aged 15–49 years in rural areas in China.13 However, few studies were conducted among middle-aged and elderly adults, who have a higher risk of chronic diseases such as hypertension and diabetes. Therefore, obtaining more accurate and comprehensive estimates of obesity and overweight is crucial for evidence-based and ethnic-specific planning and an evaluation of the currently implemented treatment strategies. The purpose of this study is to provide the most recent national estimates of obesity and overweight among Chinese adults aged 40 years and above according to the China National Stroke Screening and Prevention Project Study (CNSSPP) survey, which was carried out in 30 provinces (excluded Tibet) in China from October 2014 to November 2015 and the details have been described in previous study.14 Excluding 61 individuals due to missing information on height and weight, a total of 726,390 participants were included in the present study. The mean age and body mass index (BMI) was 57.2 (standard deviation (SD) 11.4) and 23.9 (SD 4.1), 53.3% were women, and 52.6% lived in rural areas. The overall standardised prevalence of combined overweight and obesity in Chinese adults aged 40 years and over was estimated as 30.3% (95% confidence interval (CI) 30.1–30.4). No significant difference was found between men and women, with 30.0% (95% CI 29.8–30.3) in men and 30.5% (95% CI 30.2–30.7) in women. The overall standardised prevalence of obesity was 3.5% (95% CI 3.4–3.6) and the prevalence was higher in women, participants aged 60∼69 years and participants living in economically developed areas. However, it was not statistically different between urban and rural areas. The overall standardised prevalence of overweight was estimated as 26.7% (95% CI 26.6–26.9), with 27.0% (95% CI 26.8–27.3) in men and 26.4% (95% CI 26.2–26.7) in women (Table 1). Overall, the prevalence of overweight and obesity was the highest among Uyghur participants (65.5%; 95% CI 64.0–67.0) and only Muslim Chinese was lower (27.1%; 95% CI 26.1–28.1) when compared with Han participants (30.6%; 95% CI 30.5–30.7). The odds ratios compared with Han participants were 1.61 (95% CI 1.37–1.90) for obesity and 1.27 (95% CI 1.16–1.38) for overweight and obesity for Mongol Chinese and for Muslim Chinese in the logistic models (Figure 1). Odds ratios and crude prevalence of obesity and overweight for ethnic groups. Age and sex-adjusted prevalence of overweight/obesity in different age, sex, region, economic level and geographical location. Obesity and overweight was defined according to the World Health Organization (WHO) (obesity: body mass index (BMI) ≥30.0 kg/m2; overweight: 25.0 kg/m2; ≤BMI: <30.0 kg/m2). North (Beijing, Hebei, Neimeng, Shanxi, Tianjin), northeast (Heilongjiang, Jilin, Liaoning), east (Anhui, Fujian, Jiangsu, Jiangxi, Shandong, Shanghai, Zhejiang), central (Henan, Hubei, Hunan), south (Guangdong, Guangxi, Hainan), northwest (Gansu, Ningxia, Qinghai, Shaanxi, Xinjiang), southwest (Guizhou, Sichuan, Xizang, Yunnan, Chongqing). The level of economic development of provinces or municipalities was defined on the basis of the gross domestic product per capita in 2014, and it was divided into three categories based on the trisection point. Age and sex-adjusted prevalence of overweight/obesity in different age, sex, region, economic level and geographical location. Obesity and overweight was defined according to the World Health Organization (WHO) (obesity: body mass index (BMI) ≥30.0 kg/m2; overweight: 25.0 kg/m2; ≤BMI: <30.0 kg/m2). North (Beijing, Hebei, Neimeng, Shanxi, Tianjin), northeast (Heilongjiang, Jilin, Liaoning), east (Anhui, Fujian, Jiangsu, Jiangxi, Shandong, Shanghai, Zhejiang), central (Henan, Hubei, Hunan), south (Guangdong, Guangxi, Hainan), northwest (Gansu, Ningxia, Qinghai, Shaanxi, Xinjiang), southwest (Guizhou, Sichuan, Xizang, Yunnan, Chongqing). The level of economic development of provinces or municipalities was defined on the basis of the gross domestic product per capita in 2014, and it was divided into three categories based on the trisection point. It is estimated that 3.9% of years of life lost and 3.8% of disability-adjusted life years was attributable to overweight/obesity in 2010;15 overweight and obesity have been determined as important risk factors for cardiovascular disease (CVD) and other diseases, especially in middle-aged and elderly adults. However, little is known about the current prevalence in the population in China, and only a national study according to CHNS conducted in 2009 reported that the prevalence of obesity and overweight was 10.9% and 15.7%, respectively, according to the World Health Organization (WHO) criterion among adults aged 18 years or older.5 Our study provided contemporary population-based estimates of the prevalence of obesity and overweight in Chinese middle-aged and elderly adults, and the age and sex-standardised prevalence was 3.5% and 26.7%, respectively. Our study indicated that the weighted prevalence of adults with a BMI of 25 or greater was 30.0% for men and 30.5% for women, which was lower than the global estimate, with 36.9% for men and 38.0% for women in 2013,16 but higher than that in individuals aged 15–49 years, with 2.5% for obesity and 22.4% for overweight and obesity.13 As we all know, there are 56 ethnic groups in China, and Chinese Han is the majority. There are many differences in culture, lifestyle, climate, economic levels, dietary patterns and even genetic backgrounds among certain ethnic groups.17, 18 In present study, we found that there were great differences in the prevalence of overweight and obesity in different ethnic groups; for example, compared with Han participants, the Uyghur population had a significantly higher prevalence of overweight and obesity, and the prevalence was lower among Muslims, which may contribute to a significant variation in culture, dietary patterns, climate environment and economic level among different ethnic groups.17, 19 The results could also be partly confirmed by another study conducted among Chinese immigrants in Australia, which showed that greater acculturation was associated with adverse CVD risk factors such as overweight/obesity.20 Besides, a different genetic background also accounts for the ethnic variations.21 However, the reasons for ethnic variation in BMI status prevalence are difficult to determine from the present study, and further study is required to explore the causes. Our results were inconsistent with a previous study among the population aged 15–49 years in rural areas, which reported that the ethnic groups of Uyghur and Muslim had higher rates of overweight and obesity than those in Han ethnic groups,13 which could be attributed to the region and age variations. In all, our study suggests that different health promotion strategies might be emphasised in different ethnic populations. Some strengths should be noted in the present study. The survey was a nationally representative study, the most recently completed, with the largest sample size to estimate the prevalence of obesity and overweight in China. Furthermore, this study provided the first direct comparison of obesity and overweight among major minority groups in China. This study had some limitations. First, our study only included Chinese adults aged 40 years and over, thus it was limited with regard to generalising the conclusion to other age groups in China. Second, for the analyses of ethnic variation, unweighted estimations are presented because ethnicity was not considered in the multistage sampling design. These findings suggest the prevalence of overweight and obesity is high and is different in different ethnic groups. Thus it is important to continue surveillance as well as to conduct public health measures based on different areas and ethnicities. The authors would like to thank all participants and all staff members in the CNSSPP study, and they also thank the CNSSPP for data support. WZL and ZXL contributed to the topic design, and XYT, XJW, WZL and DJC performed the literature search, analysis and interpretation of data. DQ and HZ helped in data collection. XYT and XJW drafted the manuscript. DMW contributed to the interpretation of data and revision of the manuscript. WZL, ZXL and ZHW were guarantors. All authors gave final approval and agreed to be accountable for all aspects of the work ensuring integrity and accuracy. The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: the study was funded by the Ministry of Finance of the People’s Republic of China (issued by Finance and Social Security (2011) document no. 61, Ministry of Finance), the Innovation Committee of Shenzhen Science and Technology (KJYY20170413162318686), and the Fundamental Research Funds for the Central Universities, Huazhong University of Science and Technology, Wuhan, China (2016YXMS215). 2018 National Social Science Fund “Research on the Construction of China’s Graded Medical System under the Shared Economy” (18ZDA085), and the Fundamental Research Funds for the Central Universities (2019kfyXJJS032). The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.