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J Am Coll Cardiol, 2006; 47:1588-1594, doi:10.1016/j.jacc.2005.11.074
(Published online 24 March 2006). © 2006 by the American College of Cardiology Foundation |
,*
,||,a
* Institute of Geriatrics, Chinese PLA General Hospital, Beijing, China
Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts
Department of Acupuncture, Chinese PLA General Hospital, Beijing, China
Department of Emergency, General Hospital of Chinese People’s Armed Forces, Beijing, China
¶ Department of Geriatric Cardiology, Chinese PLA General Hospital, Beijing, China
|| Channing Laboratory, Department of Medicine, Harvard Medical School and Brigham and Women’s Hospital, Boston, Massachusetts
Manuscript received September 27, 2005; revised manuscript received November 23, 2005, accepted November 28, 2005.
* Reprint requests and correspondence: Dr. Yao He, Institute of Geriatrics, Chinese PLA General Hospital, 28 Fuxing Road, Beijing 100853, China. (Email: yhe301{at}x263.net).
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Abstract |
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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.
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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.
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Methods |
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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.
Physical examinations. 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).
Statistical analysis. 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 t test 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).
Ethical considerations. 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.
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Results |
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5.6 mmol/l) was used, the MetS prevalence was 23.2% for men, 46.1% for women, and 36.8% for all participants.
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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.
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Discussion |
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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.
Conclusions. 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.
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Footnotes |
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a Dr. Hu is partly supported by the American Heart Association Established Investigator Award. 
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