Metabolic Syndrome Fact Sheet 2021: Executive Report

Metabolic syndrome (MetS) is a set of risk factors for cardiovascular disease that is considered to be related to insulin resistance, which include abdominal obesity, dyslipidemia, impaired glucose tolerance, and hypertension.1 MetS is common and increasing in prevalence worldwide, which is largely related to the increasing number of individuals with obesity and sedentary lifestyle.2, 3 MetS is associated with a higher risk of cardiovascular events4, 5 and is also closely associated with type 2 diabetes mellitus.6 MetS has also been linked to chronic kidney disease,7, 8 some cancers, and even all-cause mortality.9 Thus, MetS is now considered a public health problem, as well as a clinical dilemma.10 Considering the fact that MetS is a pre-condition of major critical health problems, updated information on the prevalence trends of MetS may be important to identify appropriate targets for the control of MetS in clinical practice.

Since 2018, the Korean Society of Cardiometabolic Syndrome (KSCMS) has published the Metabolic Syndrome Fact Sheet based on the Korea National Health and Nutrition Examination Survey (KNHANES), a nationwide survey conducted by the Korean Centers for Disease Control and Prevention (KCDC).11 The purpose of this Metabolic Syndrome Fact Sheet is to provide nationally representative statistics on the prevalence and recent trends of MetS in Korea. The 2021 Metabolic Syndrome Fact Sheet focused on recent trends in the prevalence of MetS in Korean adults aged ≤19 years and investigated the prevalence of MetS by social factors. Moreover, this fact sheet analyzed the prevalence of MetS according to health behaviors and socioeconomic status to determine the association between MetS and social factors. To investigate the overall prevalence of MetS in Korea, we used data obtained by the Korea National Health and Nutrition Examination Surveys (KNHANES) IV (2007–2009), V (2010–2012), VI (2013–2015), and VII (2016-2018) that are surveys of a representative sample of the Korean population.

The present article is an executive summary of the 2021 Metabolic Syndrome Fact Sheet by KSCMS regarding the prevalence of MetS among Korean adults from 2007 to 2018 and its related factors.

In accordance with the harmonizing worldwide consensus criteria of MetS issued by International Diabetes Federation, National Heart Lung and Blood Institute, American Heart Association, World Heart Federation, International Atherosclerosis Society, and International Association for the Study of Obesity modified National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) criteria, MetS was defined as the presence of three or more of the following components12: 1) abdominal obesity, defined as a waist circumference of ≥90 cm for males or ≥85 cm for females (following Korean specific cutoffs for abdominal obesity defined by the Korean Society of Obesity13); 2) hypertriglyceridemia, defined as a serum triglyceride concentration of ≥150 mg/dL, or specific treatment for this lipid abnormality; 3) low high-density lipoprotein (HDL) cholesterol level, defined as a serum HDL cholesterol concentration <40 mg/dL for males or <50 mg/dL for females, or specific treatment for this lipid abnormality; 4) high blood pressure, defined as a systolic blood pressure (SBP) of ≥130 mmHg and a diastolic blood pressure (DBP) of ≥85 mmHg, or treatment with antihypertensive agents; and 5) high fasting glucose level, defined as a fasting serum glucose level of ≥100 mg/dL or current use of antidiabetic medication.

The overall prevalence of MetS remained stable or decreased slightly from 2007 to 2014, and then increased since 2015. The prevalence was 21.6% in 2007, 19.5% in 2014, and 22.9% in 2018. The increasing trend in the prevalence of MetS was prominent among men from 22.5% in 2007 to 27.8% in 2018; meanwhile, the prevalence of MetS decreased slightly among women from 20.8% in 2007 to 17.9% in 2018 (Figure 1).

Figure 1
Annual prevalence trend of metabolic syndrome by sex from 2007 to 2018.

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From 2007 to 2018, the prevalence of MetS increased across most age groups, especially those in their 20s, 30s, and 40s. In the 60s age group, the prevalence of MetS has continuously decreased from 47.5% in 2007 to 41% in 2018. In the 70s age group, while the MetS prevalence decreased from 46.8% in 2007 to 31.5% in 2014, it has dramatically increased since 2015 (Figure 2). The prevalence of MetS among men increased in all age groups, and it remarkably increased among men in their 30s (from 19% to 24.7%) and 40s (from 25.2% to 36.9%) over the past 12 years. The steady deterioration of metabolic abnormalities in these working age groups may be due to unhealthy behaviors such as a sedentary lifestyle, high-risk drinking, and smoking.14 Meanwhile, the prevalence of MetS among women has decreased in the 50s and 60s and has remained stable in the 20s, 30s, and 40s since 2007. However, the prevalence among women has increased remarkably since 2015 in their 70s (34.9% in 2014 to 53.5% in 2018). Likewise, an increasing trend in the prevalence of MetS was observed among men in their 70s. While the prevalence of MetS among adults aged ≥65 years decreased from 2007 to 2014, it has risen sharply since 2015 among older Korean adults of both sexes (Figure 3). This age- and sex-specific prevalence pattern is similar to the prevalence of obesity in Korea recently released by the Korean Society for the Study of Obesity.15 These findings indicate that more aggressive lifestyle interventions and management strategies in these age groups are warranted to lower the burden of metabolic disease.

Figure 2
Annual prevalence of metabolic syndrome in total population (A), men (B), and women (C) according to age groups from 2007 to 2018.

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Figure 3
Annual prevalence of metabolic syndrome among adults aged ≥65 years.

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The trends in the annual prevalence rates of individual abnormalities among MetS components by sex from 2007 to 2018 are shown in Figure 4. Over time, the overall prevalence of elevated waist circumference, high blood pressure, and high fasting glucose levels has increased. Among the components of MetS, the increasing trend in the prevalence of high fasting glucose levels was the most noticeable over the past 12 years in both sexes. The prevalence of elevated waist circumference and high blood pressure also showed an increasing trend, especially in men. The prevalence of reduced HDL-cholesterol levels has continuously decreased since 2007 (from 42.6% in 2007 to 28.3% in 2018). The overall prevalence of hypertriglyceridemia has not changed over the past 12 years, with a slight increasing trend among men and a slight decreasing trend among women since 2007. In men, an overall increasing tendency was observed in the abnormalities of the MetS components, except for the reduced HDL-cholesterol level. In women, an overall decreasing tendency was observed in the prevalence of most MetS component abnormalities, except for high blood pressure and high fasting glucose.

Figure 4
Prevalence trend of each metabolic syndrome component from 2007 to 2018.
HDL = high-density lipoprotein.

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Based on the KNHANES VII data (2016–2018), the current prevalence of MetS among Korean adults aged ≥19 years was 23%, and it was 27.7% among adults aged ≥30 years (Figure 5). The prevalence of MetS among adults aged ≥65 years was 45.3%. The prevalence of MetS increases with age. The prevalence exceeded 40% in men in their 60s, while for women, it exceeded 50% in their 70s. While the prevalence has sharply inclined in men in their 30s, it has dramatically risen in women in their 50s. We assume that this remarkable increase in the MetS prevalence among women aged ≥50 years may be related to menopause. The prevalence of MetS was higher in men than in women across most age groups, except in individuals aged 70 years and older. In individuals aged 70 years and older, MetS was more prevalent in women than in men (37.8% vs. 53%). The most prevalent abnormalities in the MetS component were high blood pressure (32.7%), followed by high fasting glucose level (29.2%), reduced HDL-cholesterol level (29.1%), hypertriglyceridemia (28.9%), and elevated waist circumference (26.9%). In comparing the MetS components, men had a higher prevalence of elevated waist circumference, hypertriglyceridemia, high blood pressure, and high fasting glucose levels than women. In contrast, women showed a higher prevalence of reduced HDL cholesterol levels than men.

Figure 5
Current prevalence of metabolic syndrome in Korea by sex (A) and by age group (B).
Data from the Korean National Health and Nutrition Examination Survey VII (2016–2018).

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The prevalence of MetS according to socioeconomic status and health behavior patterns is shown in Figures 6 and 7. The prevalence of MetS was higher among individuals with lower educational levels. This trend was observed in both men and women. Similar to the trend with the association between MetS and education level, the inverse association between MetS and educational level was observed in the KNHANES VII (2016–2018) data for both sexes (Figure 6). In terms of health behaviors, the prevalence of MetS was higher in current smokers and high-risk drinkers. Moreover, the prevalence was higher in subjects who did not exercise regularly (Figure 7). The regional differences in the prevalence of MetS are shown in Figure 8. The highest MetS prevalence rates in 2016–2018 were found in Jeonnam (34.7%), Gangwon (30.7%), Chungbuk (30.6%), and Jeonbuk (30.4%). The prevalence of MetS is higher in rural residents than in urban residents, and it has also remarkably increased, especially in rural regions over the past 12 years.

Figure 6
Prevalence of metabolic syndrome among Korean adults according to family income (A) and educational level (B).

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Figure 7
Prevalence of metabolic syndrome according to smoking status (A), alcohol consumption pattern (B), and exercise pattern (C).
Current smokers were defined as those who smoked at least five packs of cigarettes during their lifetime and were smoking at the time of the survey. High-risk drinking was defined more than 7 glasses in men or 5 glasses in women on the same occasion on each of 2 or more a week. Regular exercise was defined as exercise for more than 30 minutes at a time and more than 5 times per week.

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Figure 8
Regional differences in the prevalence of metabolic syndrome from 2007 to 2018 in Korea.
Data are presented as percentage.

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The Metabolic Syndrome Fact Sheet 2021 provides representative enumerated estimates of the prevalence of MetS and its trend in Korean adults from 2007 to 2018. The overall prevalence of MetS in Korea remained nearly stable from 2007 to 2014 and then increased since 2015. The increasing trend in the prevalence of MetS was prominent among men in their 30s and 40s. The prevalence of MetS has also increased dramatically in adults aged 70 years and older since 2015. In 2016–2018, approximately 23% of adults aged ≥19 years in Korea had MetS, and approximately 50% of adults aged ≥65 years were estimated to have MetS.16 The latter was a curious and important finding in the aging Korean population. Furthermore, an increased prevalence of MetS in subjects with a lower educational level, lower family income, and rural residents was observed. The prevalence of MetS was also higher in participants with bad health behavior patterns. This highlights the need for organized public planning and systematic national management strategies for MetS regarding socioeconomic factors. A better understanding of the MetS epidemic and the striking disparities in social factors in relation to MetS in Korea will be helpful in the provision of appropriate interventional strategies for controlling cardiometabolic risks in Korean adults.