Author + information
- Received September 27, 2005
- Revision received November 23, 2005
- Accepted November 28, 2005
- Published online April 18, 2006.
- Yao He, MD, PhD⁎,†,⁎ (, )
- Bin Jiang, MD, PhD‡,
- Jie Wang, MD, PhD§,
- Kang Feng, MD⁎,
- Qing Chang, MD⁎,
- Li Fan, MD¶,
- Xiaoying Li, MD¶ and
- Frank B. Hu, MD, PhD†∥,a
- ↵⁎Reprint requests and correspondence:
Dr. Yao He, Institute of Geriatrics, Chinese PLA General Hospital, 28 Fuxing Road, Beijing 100853, China.
Objectives This study sought to assess the prevalence of the metabolic syndrome (MetS) and its association with cardiovascular disease (CVD) in elderly Chinese people.
Background The information available about the prevalence of MetS based on the National Cholesterol Education Program (NCEP) and the International Diabetes Federation (IDF) in China is limited.
Methods We conducted a population-based cross-sectional study in an urban Beijing sample of 2,334 participants age 60 to 95 years (943 men, 1,391 women). The CVD included diagnosed coronary heart disease (CHD), stroke, and peripheral arterial disease (PAD).
Results The prevalence of MetS by the NCEP criteria was 30.5% (17.6% in men, 39.2% in women). Use of the new IDF definition significantly increased the prevalence to 46.3% (34.8% in men, 54.1% in women). Odds ratios (OR) for CHD, stroke, PAD, and CVD in those with MetS using the NCEP criteria were 1.43 (95% confidence interval [CI] 1.18 to 1.74), 1.45 (95% CI 1.14 to 1.85), 1.47 (95% CI 1.18 to 1.84), and 1.50 (95% CI 1.25 to 1.81), respectively. Corresponding ORs using new IDF criteria were 1.69 (95% CI 1.40 to 2.02), 1.58 (95% CI 1.26 to 2.00), 1.42 (95% CI 1.14 to 1.76), and 1.73 (95% CI 1.46 to 2.07), respectively. Those who met the IDF but not the NCEP criteria (n = 436, 18.7%) had significantly elevated ORs for CHD (1.66, 95% CI 1.31 to 2.10) and stroke (1.53, 95% CI 1.13 to 2.06).
Conclusions The MetS is highly prevalent in elderly people in Beijing, particularly among women. Individuals with MetS defined by either criteria are at significantly elevated ORs for CHD, stroke, and PAD. The IDF criteria seem to be better suited than the NCEP criteria for screening and estimating risk of MetS in Chinese people.
During the past two decades, China has experienced rapid economic growth and the ageing of its population. Resulting changes in lifestyle and longer life expectancy have led to an increased burden of cardiovascular and other chronic diseases (1,2). The metabolic syndrome (MetS) is characterized by a clustering of cardiovascular risk factors, including abdominal obesity, high blood pressure, increased glucose concentration, and dyslipidemia. The syndrome is associated with the development of diabetes and cardiovascular disease (CVD) (3,4) and increased risk of mortality from CVD and all causes (5,6). Two recent definitions of MetS have been proposed by the U.S. National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) and the World Health Organization (WHO) (7,8). In April 2005, the International Diabetes Federation (IDF) proposed a new definition of MetS that includes central obesity as a prerequisite and gender- and ethnicity-specific cutoff points for central obesity as measured by waist circumference (9).
Few studies have published information on the prevalence of the MetS in Chinese populations (10–14). Most published studies used NCEP ATP III and WHO-modified Asian criteria to define MetS. Thus far, no study has compared the prevalence defined by NCEP ATP III criteria with that defined by the new IDF criteria. Also, data on the relationship between the MetS and CVD in developing countries are limited. This study intended to determine the prevalence of MetS as defined by NCEP ATP III and IDF criteria and to examine the relation between MetS and CVD in a population-based survey of elderly Chinese people in Beijing, China.
Subjects and study design
This study was a population-based cross-sectional survey of elderly people living in the Wanshoulu Community of Haidian District in Beijing, China. A two-stage stratified sampling method was used. First, 9 residential communities or streets (about 300 to 600 households) were randomly selected from a total of 94 residential communities in the Wanshoulu area. Secondly, all individuals were chosen from the selected streets, but only one participant was randomly selected from each household. Between April 2001 and March 2002, 2,680 people age 60 years or older were selected and invited for screening. A total of 2,334 subjects (943 men, 1,391 women) completed the survey, yielding a response rate of 87.1% (83.5% in men, 89.7% in women), and they accounted for 11.4% of elderly residents in the Wanshoulu area.
Collection of data
We identified eligible people by their age and documents of residence and invited them to a community clinic by letter or telephone. Each participant was interviewed and completed a standardized questionnaire that included a range of demographic factors, aspects of medical history, family history of CVD, and lifestyle. The physical examinations and interview were carried out by trained nurses and physicians. The participants’ ages ranged from 60 to 95 years, with a mean of 68.5 ± 5.4 years. Categories of educational attainment included 0 years, never attended primary school; ≤6 years, attended only primary school; ≤9 years, completed middle school; ≤12 years, completed high school or the equivalent; and ≥13 years, completed a university or other tertiary degree. Marital status was classified into four categories: single, married, divorced, or widowed. The categories of smoking were never smoking, former smoking, and current smoking. Current drinking was defined as average alcohol consumption of more than 10 g of absolute alcohol per day for more than 1 year in the past 5 years. According to the average hours per day, physical exercise was divided into three levels: <1 h, 1 to 3 h, or ≥4 h.
Height was measured in meters (without shoes), and weight in kilograms (with heavy clothing removed and 1 kg deducted for remaining garments). Body mass index was calculated as weight in kilograms divided by the square of height in meters. We measured waist circumference on standing subjects with a soft tape midway between the lowest rib and the iliac crest. Hip circumference was measured over the widest part of the gluteal region, and the waist-to-hip ratio was calculated as a measure of central obesity. Two blood pressure recordings were obtained from the right arm of patients in a sitting position after 30 min of rest; measurements were taken in 5-min intervals, and mean values were calculated. Overnight fasting blood specimens were obtained for measurement of serum lipids and glucose. Plasma glucose was measured using a modified hexokinase enzymatic method. Concentrations of total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides were assessed enzymatically with commercially available reagents.
Definition of MetS
The first definition of MetS was that of the NCEP, and a participant was deemed to have MetS when three or more of the following criteria were satisfied: 1) high blood pressure: blood pressure ≥130/85 mm Hg or known treatment for hypertension; 2) hypertriglyceridemia: fasting plasma triglycerides ≥1.7 mmol/l; 3) low HDL: fasting HDL cholesterol <1.0 mmol/l in men, <1.3 mmol/l in women; 4) hyperglycemia: fasting glucose level of ≥6.1 mmol/l or known treatment for diabetes; 5) central obesity: waist circumference >88 or >102 cm in women and men, respectively. A modified NCEP definition using a lower cutoff point of fasting glucose (≥5.6 mmol/l) was also used in the present study (15).
The second definition of MetS was the new IDF definition, and a person was considered to have MetS if they had central obesity (waist circumference ≥90 cm in men, ≥80 cm in women for Chinese people) plus any two of the following four factors: the criteria for high blood pressure, hypertriglyceridemia, and reduced HDL cholesterol were the same as those of the NCEP, but the criterion for raised fasting plasma glucose was a level ≥5.6 mmol/l.
Diagnosis of CVD
Hypertension was defined as diastolic blood pressure of ≥90 mm Hg, systolic blood pressure of ≥140 mm Hg, or current medication for hypertension (as defined by WHO 1999). Coronary heart disease (CHD) and stroke were defined using the WHO MONICA criteria (16). There were 784 CHD patients (68 myocardial infarction, 716 stable angina). Myocardial infarction was diagnosed by a representative set of electrocardiogram, cardiac enzyme values, and typical symptoms. Angina was defined as use of nitroglycerine, experience of typical chest pain, and electrocardiogram changes compatible with ischemic heart disease (58% of the cases were validated against by exercise test or B-mode ultrasonography). There were 378 cases of stroke (248 ischemic, 70 hemorrhagic, 60 other types). Strokes were defined as events requiring hospitalization; this information was verified from local hospital records, and 83% of the cases were confirmed using computed tomography and magnetic resonance imaging. Peripheral arterial disease (PAD) was assessed as positive intermittent claudication by the WHO/Rose questionnaire or an ankle-arm systolic blood pressure index <0.9 (17). Cardiovascular disease in the present study was defined by the presence of one or more of these three outcomes: CHD, stroke, and PAD. Subjects with a fasting plasma glucose level of 7.0 mmol/l and/or a 2-h plasma glucose level of 11.1 mmol/l during an oral glucose tolerance test and/or who were receiving antidiabetic medications were diagnosed with diabetes mellitus. The diagnosis of cardiovascular events was based on self-reports, confirmed by hospital medical records and further clinical examinations carried out at the time of the survey (including electrocardiogram and ankle-arm systolic blood pressure index).
Data were entered (double entry) and managed using Microsoft Access (Microsoft Corp., Redmond, Washington). Age- and gender-specific prevalence of MetS were calculated using NCEP and IDF criteria. The ttest and Chi-square test were used to examine differences in continuous and categorical variables, respectively, between men and women. Logistic regression was used to calculate odds ratios (ORs) and their 95% confidence intervals (CIs). Potential confounders (age, gender, marital status, years of education, smoking, alcohol consumption, hours per day of physical exercise, and family histories of CHD or stroke) were adjusted. All analyses were conducted using SPSS (version 11, SPSS Inc., Chicago, Illinois).
The committee for medical ethics of the Chinese PLA General Hospital approved the study. Each participant signed an informed consent form before completing the questionnaire.
General characteristics of the 2,334 subjects (943 men, 1,391 women) are given in Table 1.There were significant differences between men and women in most of the covariates.
Prevalence of MetS
Table 2shows that the proportion of the 2,334 Chinese elderly people with individual components of MetS (i.e., hyperglycemia, high blood pressure, hypertriglyceridemia, low HDL cholesterol, central obesity), and the number of components. There was no clear age-related increase in the prevalence of individual components of MetS or of MetS in this population. However, we found a higher prevalence of MetS components in women than in men based on NCEP or IDF criteria. Prevalence of central obesity was considerably higher (67.3% vs. 29.6%) with the IDF criteria than with the NCEP criteria; the proportion of MetS components in men and women also differed, with a prevalence of MetS of 34.8% versus 17.6% in men and 54.1% versus 39.2% in women, respectively. When the modified NCEP definition with a lower cutoff point of fasting glucose (≥5.6 mmol/l) was used, the MetS prevalence was 23.2% for men, 46.1% for women, and 36.8% for all participants.
Figure 1describes the prevalence of CHD, stroke, PAD, and CVD in the different groups of MetS components based on the NCEP and IDF criteria. We found a significantly higher prevalence of CHD, stroke, PAD, and CVD with an increasing number of MetS components.
Odds of CVD and MetS
Table 3shows the ORs for MetS by NCEP and IDF criteria, and their individual components associated with CHD, stroke, PAD, and CVD. Of the five MetS components, the ORs of hypertension and central obesity (particularly as defined by the IDF Chinese waist circumference criteria) were higher than those of the other three clinical outcomes. Individuals with MetS defined by either criteria were at significantly elevated ORs for CHD, stroke, and PAD. However, the ORs of CVD associated with MetS defined by IDF seemed to be stronger than those associated with MetS defined by NCEP criteria. We conducted separate analyses for men and women. The ORs of CVD according to MetS defined by IDF criteria were 1.77 (95% CI 1.34 to 2.34) for men and 1.71 (95% CI 1.37 to 2.13) for women. Interestingly, using a lower cutoff point for fasting glucose increased the ORs of CVD for MetS defined by NCEP criteria. Additional adjustment for use of antihypertensive and cholesterol-lowering medications only slightly attenuated these ORs. Also, adjustment for total or LDL cholesterol did not appreciably alter the results.
Using the IDF criteria, we identified 436 subjects (18.7%) with MetS who did not meet the NCEP criteria. Compared with those without MetS, these participants had significantly higher odds of CHD, stroke, and CVD (Table 3). Interestingly, 67 subjects (3%) who met the NCEP criteria but not the IDF criteria did not have a significantly elevated odds of CVD compared with those without MetS.
When diabetic patients (n = 362, 15.5%) were excluded from the analyses, the ORs of CVD associated with MetS defined by IDF were somewhat attenuated, but they remained significant. The adjusted ORs of CHD, stroke, PAD, and total CVD according to MetS defined by the IDF criteria were 1.57 (95% CI 1.28 to 1.91), 1.53 (95% CI 1.18 to 1.99), 1.36 (95% CI 1.07 to 1.73), and 1.55 (95% CI 1.28 to 1.87), respectively.
This investigation of MetS focused on Chinese elderly people 60 years or older—a group at higher risk of developing CVD and one that makes it easy to observe and analyze the relation between MetS and the risk of CVD. This is a random cluster-selected sample with a relatively high response rate. Approximately 13% of eligible subjects dropped out of the study (e.g., left original residence, or had incomplete interviews or examinations), but no statistically significant differences were detected between subjects with complete and those with incomplete data. Consequently, the prevalence of MetS and its association with CVD can be generalized with confidence to similar populations in urban Beijing, China.
Although the WHO and the NCEP have proposed definitions of MetS, a universally accepted definition does not exist. The WHO criteria are more complex than the NCEP criteria and include measurement of microalbuminuria and plasma insulin levels. Lack of standardization and availability of assays for insulin and microalbuminuria in Asian populations makes the NCEP ATP III guidelines preferable; they can easily be applied in the primary care setting, and results can be readily compared with those from Western studies.
However, the recommended cutoff points for waist circumference in the NCEP definition may be inappropriate for Asian populations because Asian people tend to have a higher percentage of body fat, particularly abdominal visceral fat, than do white people with the same body mass index, and thus the use of the NCEP criteria in Chinese and other Asian populations could underestimate the prevalence of MetS and fail to identify many individuals at risk for future CVD (14). The IDF definition requires central obesity as a requisite for diagnosis of the MetS and proposes ethnicity-specific cutoff points for waist circumferences (9). Although those cutoff points are still a matter of debate, the cutoff points for Chinese people according to the IDF criteria are lower than those according to the NCEP criteria (90 cm vs. 102 cm in men, 80 cm vs. 88 cm in women). This explains why the prevalence of MetS increased substantially when the IDF definition rather than the NECP definition was used (46.3% vs. 30.5%). The prevalence of MetS in our population defined by the IDF criteria was similar to that in the U.S. population in the same group defined by the NCEP criteria (18).
In our study, the prevalence of MetS was much higher in women than in men—results that are consistent with those from mainland China, Taiwan, and Hong Kong (10–13). The gender difference is primarily attributable to a higher prevalence of abdominal obesity and low HDL cholesterol in women than in men. However, the association between the MetS and prevalence of CVD was similar between men and women.
Subjects with MetS according to either the IDF or the NCEP criteria had a significantly higher odds of CHD, stroke, and PAD. The ORs for these cardiovascular end points associated with MetS seem to be somewhat higher when the IDF definition was used than when the NCEP definition was used. Also, almost 20% of subjects met the IDF criteria but not the NCEP criteria, and they had a significantly increased odds of CHD and stroke. These data suggest that the new IDF criteria are more suitables than the NCEP criteria for screening higher-risk individuals and for estimating the risk of CVD from MetS in the Chinese population.
To the best of our knowledge, this report is the first to examine the relation between the prevalence of MetS and the odds of CHD, stroke, PAD, and CVD in a population-based study in China. The clinical importance of MetS is related to its putative impact on cardiovascular morbidity and mortality; in the present study, the risks of CHD, stroke, PAD, and total CVD were 50% to 70% higher in subjects with MetS than in those without MetS. This association remained significant even after excluding diabetic patients. Although the prevalence and ORs of the individual components of MetS varied widely, hypertension and central obesity seem to be more widespread in the elderly Chinese population. This pattern of the individual components of MetS in elderly people is consistent with other Chinese data (12,19,20). Among the individual components of MetS, hypertension and central obesity seem to have the strongest associations with prevalence of CVD. These findings underscore that it is important to prevent and treat both overall MetS and individual components.
Admittedly, the cross-sectional nature of this study limits our causal inference. However, the temporal relationships between individual components of the MetS and CVD have been well established. In addition, our estimates on the relationship between the MetS and cardiovascular outcomes may be underestimated because our participants were elderly survivors. Another potential concern is that HDL cholesterol, triglyceride, and blood glucose levels were measured only once, which might have led to random errors.
Our study indicates that MetS is highly prevalent in the elderly Chinese people living in urban Beijing, especially among women. New IDF criteria of MetS seem to be more pertinent than those from NCEP for screening and estimating risk in Chinese populations. Our evidence shows that in developing countries, individuals with MetS are at increased risk for CHD, stroke, and PAD. In the elderly Chinese population, hypertension and central obesity are more prevalent than the other components of MetS. Developing effective public health strategies for the prevention, detection, and treatment of MetS should be an urgent priority to reduce the social and medical burden of CVD in China.
↵a Dr. Hu is partly supported by the American Heart Association Established Investigator Award.
This study was supported by research grants from the Main State Basic Research Development Program of China (G2000057006) and the Health Service in the Health Ministry of China (2001-5-006).
- Abbreviations and Acronyms
- coronary heart disease
- confidence interval
- cardiovascular disease
- high-density lipoprotein
- International Diabetes Federation
- low-density lipoprotein
- metabolic syndrome
- NCEP ATP III
- National Cholesterol Education Program Adult Treatment Panel III
- odds ratio
- peripheral arterial disease
- World Health Organization
- Received September 27, 2005.
- Revision received November 23, 2005.
- Accepted November 28, 2005.
- American College of Cardiology Foundation
- Wu Z.,
- Yao C.,
- Zhao D.,
- et al.
- Haffner S.M.,
- Valdez R.A.,
- Hazuda H.P.,
- Mitchell B.D.,
- Morales P.A.,
- Stern M.P.
- Isomaa B.,
- Almgren P.,
- Tuomi T.,
- et al.
- Trevisan M.,
- Liu J.,
- Bahsas F.B.,
- Menotti A.,
- Risk Factor and Life Expectancy Research Group
- ↵IDF. The IDF Consensus Worldwide Definition of the Metabolic Syndrome. Available at: http://www.idf.org/home/index.cfm?=unode=1120071E-AACE-41D2-9FA0-BAB6E25BA072. Accessed April 14, 2005.
- Chuang S.C.C.,
- Tsai S.,
- Chou P.
- Tan C.E.,
- Ma S.,
- Wai D.,
- Chew S.K.,
- Tai E.S.
- Grundy S.M.,
- Cleeman J.I.,
- Daniels S.R.,
- et al.
- ↵(1983) WHO/MONICA-Project: Multinational Monitoring of Trends and Determinants in Cardiovascular Diseases (MONICA Project) and Manual of Operation (World Health Organization, Cardiovascular Disease Unit, Geneva, Switzerland).
- Newman A.B.,
- Siscovick D.S.,
- Manolio T.A.,
- et al.,
- Cardiovascular Heart Study (CHS) Collaborative Research Group