Background
Metabolic syndrome (MetS) is a clustering of metabolic risk factors including central obesity, elevated blood pressure, increased fasting plasma glucose, high serum triglycerides, and low high-density cholesterol levels [
1]. People with metabolic syndrome are at increased risk for atherosclerosis, peripheral vascular disease, coronary heart disease, myocardial infarction, stroke, and type 2 diabetes [
2‐
5], which are the leading causes of death and disability worldwide [
6]. However, metabolic syndrome and its deadly consequences can be preventable and treated by maintaining a healthy weight, eating a healthy diet, getting adequate physical activity, and following healthcare providers’ instructions [
7,
8]. To prevent from premature deaths and illnesses, it is necessary to evaluate the magnitude of metabolic risk factors and identify population groups at risk of chronic diseases.
Despite the worldwide importance of MetS, relatively little has been known about its actual prevalence and its risk factors in Vietnam. According to the US National Cholesterol Education Adult Treatment Panel III (NCEP ATPIII) criteria [
9], the prevalence of MetS in Ho Chi Minh city, the biggest city in the Southern Vietnam, was 12% in adults aged ≥ 20 years in 2001 [
10], and 8.2% population aged ≥ 15 years in 2003 suffered MetS in Khanh Hoa, a coastal province of South Central Vietnam [
11]. The MetS prevalence was found in 4.6% children aged 13–16 years in Ho Chi Minh City in 2007 [
12]. To date, there has been a limited data on the MetS and associated factors in rural areas with more than 71% of the total population in Vietnam [
13]. In addition, a better knowledge of the components of MetS should provide important insights in the pathogenesis of MetS, allowing the evaluation of better interventions at both population level and individual level to reduce the burden of MetS. Therefore, we conducted a cross–sectional study to identify the prevalence of MetS and its components, as well as associated factors for MetS in rural Vietnamese population.
Discussion
People with metabolic syndrome are at high risk for developing type 2 diabetes and cardiovascular diseases. However, there have so far been few papers studying the MetS prevalence in Vietnam. The present study indicated that the total age– and sex–adjusted prevalence (95% CI) of MetS was 16.3% (14.0–18.6) in the middle-aged population in the Red River Delta region of Vietnam; and the prevalence of high TG, low HDL-C, elevated blood pressure, high plasma glucose, and central obesity were 43.2, 42.0, 29.2, 14.3, and 12.3%, respectively. In addition, because Ha Nam province is thought to be a typical rural province in Red River Delta Region with a population about 3727000 adults aged 40–64 years [
13], we could estimate the number of residents with MetS, high TG, low HDL-C, elevated blood pressure, high plasma glucose, and central obesity are 607500, 1610000, 1565000, 1088000, 533000, and 458400, respectively. These estimated numbers can help to show the burden of MetS in the region and it is crucial for local health managers to make activity plan to control MetS and its components.
Using the NCEP ATPIII criteria adapted for Asians, this MetS prevalence (16.3% in 2009) in rural population aged 40–64 years seems to be lower than that (about 18.1% in 2001) in urban population aged 35–64 years in the biggest city [
10] and higher than that (about 10% in 2003) in a coastal population aged over 35 years in the South Central Vietnam [
11]. In comparison with other populations in Asia with the adapted NCEP ATPIII criteria, our study reported lower MetS prevalence than those reported in Malaysia [
16], Eastern India [
17], China [
18], Indonesia [
19], Philippine [
20], Japan [
15], and South Korean [
21]. The MetS prevalence in this study was compatible with that in Bangkok, Thailand [
22] and higher than that reported in Taiwan [
23]. This difference could be explained by the traditional lifestyle may remain conservative in rural areas and by the “nutrition transition” [
24] still keeps low stage in this process with 11% underweight subjects (BMI < 18.5 kg/m
2) and 7.7% obese subjects (BMI ≥ 25 kg/m
2) in the present study.
In this study, the most frequent component of MetS was high TG (43.2%), followed by low HDL-C (42.0%), elevated blood pressure (29.2%), high plasma glucose (14.3%), and central obesity (12.3%). In Vietnam, low HDL-C prevalence was reported to be the second-highest rate in rural area and another coastal area [
11]. In addition, the contrast of central obesity prevalence was observed: lowest in rural and costal areas
vs. highest in urban area [
10]. Thus, MetS components vary in distribution in different geographical regions.
In terms of the subjects with normal BMI (18.5 ≤ BMI < 23 Kg/m
2), the prevalences of MetS, central obesity, elevated blood pressure, increased plasma glucose, high TG, and low HDL-C were 12.5 (11.2 - 13.7), 4.3 (3.8 - 4.8), 26.5 (24.5 - 28.5), 12.9 (11.5 - 14.2), 42.6 (40.0 - 45.3), and 45.7% (43.0 - 48.4), respectively. Another study in the biggest city of Vietnam [
25] showed that the rates of central obesity, hypertension, lipid metabolism disorders, and glucose metabolic disorders were 17.5, 29.3, 77.8 and 35.6%, respectively, in the subjects with normal BMI. The above data indicated that the prevalences of MetS and its components were relatively high even among those with BMI in normal ranges and at younger age.
With regard to the gender difference in MetS, we found that the prevalence of MetS, central obesity, and low HDL-C was remarkably higher in women compared to men, while prevalence of elevated blood pressure and high TG was much higher in men compared to women. It is in line with several studies in Vietnam [
11], India [
26], Korea [
21,
27], whereas it is different from other studies in ten large cohorts in European countries [
28], and in Ghana [
29]. This discrepancy can be explained by the different WC cut-off to define central obesity, age structure and characteristics of studied populations.
Predictors for an increased risk of developing MetS are very important to prevent a population from this disorder effectively. The present study indicated that residence, age, BMI, marital status, and siesta time per day were the most significantly associated factors for MetS. The association was found to be statistically significant in univariate analysis, replicated in multivariate analysis adjusted for socioeconomic conditions (age, sex, residence, marital status, income level, occupation, and educational levels), and lifestyle - related factors (alcohol consumption, smoking, time spending for night’s sleep, siesta, sitting, and watching TV). These associated factors should be validated in prospective studies for building prognosis models to early detection of MetS in rural Vietnamese populations, to warn people off high risk of MetS, and to counsel them how to prevent from MetS and its components.
Among the 5 Mets components, central obesity and elevated blood pressure are easy, non-invasive, and feasible criteria to use as the first step in the screening strategy for MetS detection in the context of developing countries with limited resources. In the present study, we used the waist circumference ≥ 90 cm for men and ≥ 80 cm for women to define central obesity [
15]; and the prevalence of central obesity was found to be 12.3% (10.4 - 14.2), showing the lowest rate among the 5 MetS components. If screening strategy recruits only subjects with central obesity for further MetS detection (i.e., central obesity and any two of the others MetS components), 12.3% of the population is included in the second step, the sex- and age- adjusted prevalence of MetS is found 6.7% (5.4 - 8.0), indicating 5.6% underestimated prevalence or 54% undetected total MetS cases. If screening strategy uses elevated blood pressure as the first criteria (SBP ≥ 130 mmHg or DBP ≥85 mmHg), then 29.2% of the population with elevated blood pressure are recruited for the second step screening; and the adjusted MetS prevalence is 11.9% (9.9 - 13.9), showing 4.4% underestimated prevalence or 35% undetected total MetS cases. When central obesity or elevated blood pressure are used for the first step and second step using fasting blood analysis of glucose and lipid profile, 38.7% of the population is selected in the second step; and the adjusted MetS prevalence is 14.3% (12.0 - 16.5) with 2% underestimated prevalence or 12.3% undetected total MetS cases. This above analysis (Additional file
3) implicates that the better screening strategy to detect MetS in the Red River Delta region should include 2 steps, in which the first step is used for recruiting subjects with central obesity or elevated blood pressure, and second step is used for further analysis of glucose and lipid profile.
This study had several limitations. First, given the cross-sectional nature of the study, this does not allow for conclusions of the causal relationships. The follow-up study is needed to evaluate the cardiovascular events to estimate the incidence and develop the prognosis tools for early MetS detection. Second, data on physical activities and food intake were not used in these findings to evaluate a potential effect of these variables in our results. Lastly, our sample was a representative sample for a rural province in the Red River Delta region, the extrapolation for other geographical regions in Vietnam (mountainous, coastal, highland, and Mekong River Delta regions) should be taken into account. It is essential to conduct a national survey to evaluate the MetS patterns in different geographical regions.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
TQB: Conceptualization of the study, study design, proposal writing, data collection, data analysis, discussion and editing of the final draft for publication. PTP, BTN, DDT: Conceptualization of the study, study design, data collection, discussion and editing of the final draft for publication. All authors approved the final draft of this article prior to submission. All authors read and approved the final manuscript.