Prevalence and distribution of metabolic syndrome and its components among provinces and ethnic groups in Indonesia

Metabolic syndrome (MetS) is a cluster of interconnected risk factors that increase the risk of cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM) [1]. Increased prevalence worldwide affects both developed countries as well as developing countries, including the Asia-Pacific region [2]. This MetS increase is in concordance with the 82% increase of the worldwide obesity pandemic over the time span of 1990 to 2010 based on the Global Burden of Disease (GBD) [3]. According to a systemic review in 2007 by Ranasinghe et al. [2], the prevalence of MetS was in the range of 11.9 to 37.1% in the Asia-Pacific region which consists of the Philippines, China, Sri Lanka, Taiwan, Singapore, South Korea, Mongolia and Malaysia with the prevalence of 11.9, 21.3, 24.3, 25.5, 26.9, 31.3, 32.8 and 37.1%, respectively, based on different MetS syndrome definitions.

Among Southeast Asian countries, Indonesia is the most populated country in this region which reached 227 million people in 2005 [4], consisting of various ethnic groups that were estimated by 2007 to be 633 [5], along with various cultures and lifestyles spread over 33 provinces [6]. Since an increasing trend in MetS prevalence was found in other regions, Indonesia might be affected simultaneously, however, little is known regarding the MetS epidemiology in this multiethnic group country.

A few studies have tried to assess the MetS prevalence in certain provinces of Indonesia separately such as in Yogyakarta (13.19%) [7], and Jakarta (28.4%) [8], based on different MetS syndrome definitions but none yet have attempted the assessment in a larger scope such as a national survey. An update for MetS prevalence that represents MetS prevalence in a national scope is warranted and will benefit national planning for future prevention of MetS clinical consequences. Concerning the variations of Indonesian inhabitants and wide distribution of Indonesian lifestyles, it was hypothesized that the distribution of metabolic syndrome prevalence and MetS components may vary among provinces and ethnic groups in Indonesia.

Disability Adjusted Life Years (DALYs) contributed by risk factors associated with MetS including high BMI, high blood pressure, high fasting plasma glucose, high total cholesterol have grown since 1990 to 2000 based on GBD [3]. Low HDL cholesterol is the most prevalent risk factor, followed by central obesity, hypertension, high triglyceride level and high fasting plasma glucose level based on a Korean study in 2011 [9]. The prevalence pattern of MetS risk factors might differ in Indonesia due to different demographic and geographical factors and hence may affect the impact of each component involved in MetS based on different MetS definitions.

Thus, the aim of this study is to determine the prevalence of metabolic syndrome and MetS components among Indonesian people based on the province and ethnic groups.

This research is the first nationwide study regarding MetS prevalence in Indonesia. The prevalence of MetS in Indonesia was 21.66%, which was in concordance with the estimation of global MetS prevalence (20–25%) by IDF [11]. In the Asia-Pacific region, the highest prevalence was found to be in Malaysia (42.5%, Harmonized definition) [12], followed by Mongolia (32.8%, IDF) [13], South Korea (31.3%, Harmonized definition) [14], China (29.7, NCEP ATP III) [15], Singapore (26.9, Harmonized Definition) [16], Taiwan (25.5, Modified NCEP ATP III) [17], Sri Lanka (24.3, IDF) [18], and Philippine (18.6%, Modified NCEP ATP III) [19], so MetS prevalence in Indonesia is the second lowest in Asia Pacific region based on this study.

There is a significant gap between MetS prevalence in Western countries such as USA (39.0, IDF) [20] compared to MetS prevalence in Indonesia (21.66%). It was shown that the national MetS prevalence in Indonesia (21.66%) is less than the urban prevalence of MetS in Jakarta (28.4%) [8], being the capital of Indonesia, hence the latter could not represent the overall prevalence of MetS in Indonesia as demographic factors play significant roles in MetS prevalence. Nevertheless, the prevalence of MetS in Jakarta in this study was 37.5% based on the 2007 survey, which showed higher prevalence compared to the previous study in Jakarta (28.4%) [8], based on the 2006 survey. Therefore, this prevalence difference gave an impression that there is a rising trend in MetS prevalence in Indonesia throughout the years.

Large MetS prevalence difference was seen in Kalimantan Island which was partly due to the limited amount of subjects representing each province. Some subjects were excluded in this study since their data were incomplete, which further reduced the sample size pool. The highest prevalence of MetS when compared among provinces was found in East Kalimantan (50%) followed by Jakarta (37.50%). Despite having only a small number of subjects in East Kalimantan who represented the province, the results were accepted because the data obtained from IFLS 4 are based on stratified random sampling which aimed to ensure estimates can be done with equal accuracy since population disparities were evident across provinces in Indonesia. This trend was consistent with one study which shown that Asians are more likely to manifest MetS compared to non-Hispanic Whites [21] especially when Indonesians had gradually adopted western lifestyles including diet.

As most subjects in this study were residing on Java island, it was not surprising that Javanese was the largest ethnic group in this study which represented 46.41% of the total subjects. Each province tend to have its own unique ethnic group which was the dominant population. This dominant residency pattern might contribute to disparity in MetS prevalence among ethnic groups since each ethnic group might have different lipid profiles, socioeconomics and lifestyle, similar as in the previous studies [22‐24]. The prevalence of MetS in Balinese is 0.67 times less than the remaining population, followed by Javanese which was 0.86 times less than the remaining population, showing lesser prevalence in these two ethnic groups. The prevalence of MetS in Acehnese was 2.1 times greater than the remaining population, followed by Sasak (1.53 times greater), Betawi (1.60 times greater) and Minangkabau (1.469 times greater). This finding tallied with the results from a study regarding lipid profiles among four ethnic groups including Minangkabau, Sundanese, Javanese and Buginese, revealed the Minangkabau ethnic group has the highest total plasma cholesterol and lowest plasma LDL cholesterol, Sundanese have the lowest plasma HDL cholesterol and Javanese have the lowest total and LDL plasma cholesterol and highest HDL plasma cholesterol [22]. Since the Javanese group had the best lipid profile, it is consonant with the finding in this study which shown MetS prevalence is significantly lower in the Javanese ethnic group compared to others. In a related study lipid profiles were consistently associated with insulin resistance because insulin affects the metabolism of HDL plasma cholesterol and triglycerides [25], hence central obesity is further developed with poor glucose and lipid control.

The top 3 most prevalent MetS components in this study were low HDL cholesterol, followed by hypertension and central obesity. This pattern was similar to one of the South America countries, Brazil, with low HDL cholesterol as the most prevalent component (59.3%), followed by hypertension (52.5%), and central obesity (38.9%) [26]. However, European countries such as Poland, displayed a different pattern starting from top to bottom, abdominal obesity (75.1%), hypertension (71%) and insulin resistance (37.3%) [27]. In Asian countries such as China, the most prevalent component was hypertension (24.52%), followed by dyslipidemia (24%) and central obesity (22.07%) [28]. Furthermore, Malaysia showed a reverse arrangement for the top 3 components, which were abdominal obesity (57.4%), hypertension (52.3%) and low HDL cholesterol (42.7%) [12]. Each country held a different pattern for the prevalence of each metabolic syndrome component, and even Malaysia as a neighbor country in the same continent showed dissimilarity, hence it is unlikely to have a standard pattern framed on each population due to wide variations of cultural background, demographic and socioeconomic factors.

Even when the low HDL cholesterol, hypertension and central obesity’s pattern was brought forward to compare among Indonesia provinces, this pattern did not apply in certain provinces such as Kepulauan Riau, Jakarta, West Java, Yogyakarta, Banten, Central Kalimantan, South Sulawesi and West Sulawesi (8 out of 20 province). It was also different in certain ethnic groups such as Sundanese, Bugis, Chinese, Nias, Toraja, Dayak, Malay, Komering, Ambonese, Manado, Acehnese, Bantenese, Cirebonese and other minority ethnic groups (14 out of 27 ethnic groups). This pattern disparity definitely had effect on the criteria used to define MetS. Central obesity was not the most prevalence component, hence by using the IDF criteria which required central obesity as a core component [11] might potentially leave out MetS subjects, which reduces the sensitivity of screening the population. However, the specific racial cut-off values for waist circumference is valuable for Asian populations as NCEP ATP III criteria had a higher cut-off value for which the latter might not include the potential MetS subjects. Therefore, the Harmonized definition was applied in this study which required 3 out of 5 risk factors in addition to specific racial cut-off values for waist circumference. This approach was consistent with the finding that shown the Harmonized definition had the highest sensitivity [29] compared to IDF and NCEP ATP III criteria. The Body Mass Index (BMI) for defining obesity in Asian populations is also lower than in Caucasian populations since the percentage of body fat is higher in Asians, as Asian population are more likely to develop T2DM and CVD at BMI ranging 22-25 kg/m² [30], therefore it is necessary to implement lower cut-off values for waist circumference in Asian populations.

Limitations of this study include the lack of plasma triglyceride data which reduced one component from the 5 risk factors. Low HDL plasma cholesterol level does not indicate the presence of high plasma triglyceride in Indonesians, which is consistent with the finding based on a study which shown low HDL plasma cholesterol and normal triglyceride level in most of the West Africans and American Africans manifested with MetS [31]. Hence, it is possible to find a pattern of high plasma triglyceride level with normal HDL plasma cholesterol subjects who may not be classified as MetS subjects. There is also no fasting plasma glucose data which reduces the hyperglycemia sample size pool, rendering the possibility of leaving out potential MetS subjects with hyperglycemia. For the cholesterol treatment, the drug class is not specified in the datasheet. Thus, we cannot differentiate whether the treatment was meant for reduced HDL-cholesterol, elevated triglyceride or elevated LDL-cholesterol. Limited amount of subjects in certain provinces further reduces the specificity of MetS prevalence, which probably results in an over-estimate or under-estimate of the MetS prevalence in those provinces. Since this study showed approximately 1 MetS Indonesian were found among every 5 Indonesians in year 2007, this finding was alarming that the exact national MetS prevalence might be higher than estimated. Furthermore, the potential underestimation of this study was definitely more superior than extrapolating from sporadic provincial studies which were deemed inconclusive.

Since this is the first nationwide study of MetS prevalence, population based strategies should be implemented to control the expansion of MetS prevalence. MetS subjects had higher medical care utilization and costs compared to non-MetS subjects which increase approximately 24% in costs with each additional risk factor [32]. Furthermore, the stakeholders related to IFLS could include fasting plasma glucose and plasma triglyceride levels in future data collections because both components are important health determinants related to CVD and T2DM and more accurate MetS incidence can be determined.

The prevalence of MetS in Indonesia is moderate with provincial and ethnic prevalence varied. Provincial and ethnic group differences in MetS prevalence ratios were observed. The top two most prevalent MetSomponents in Indonesian were low HDL cholesterol and hypertension.