Introduction
Metabolic syndrome is the clustering of several metabolic abnormalities, including visceral obesity, hypertension, impaired glucose tolerance, and dyslipidemia, which raises the risk of type 2 diabetes (T2D) and cardiovascular disease [
1‐
3]. Patients with both T2D and metabolic syndrome have an increased risk of developing cardiovascular disease compared to patients with T2D without metabolic syndrome [
4,
5].
Obesity is a key aspect of metabolic syndrome, with obesity-related pathophysiology frequently postulated to underlie the association of metabolic syndrome and cardiovascular disease [
3]. Some clinical features of T2D differ between patients from East Asian countries and those from Western countries [
1,
6]. Notably, Japanese and other East Asian patients with T2D have a lower mean body mass index (BMI) but a higher percentage of visceral fat at any given BMI than non-Asian patients [
6]. In both Japanese and non-Asian populations, higher BMI and percentage of visceral fat have been associated with higher risks for metabolic syndrome, T2D, and cardiovascular disease [
3,
7‐
13]; however, Asian patients with T2D have a higher incidence of renal comorbidities and ischemic stroke but a lower incidence of coronary heart disease and peripheral vascular disease compared to non-Asian populations [
14]. A better understanding of the trends in the prevalence of metabolic syndrome in Japanese patients with T2D and the impact of BMI on these trends is required to improve metabolic health in this population.
The prevalence of metabolic syndrome in the general population of Japan aged over 40 years has been reported to be 25.9–28.5%, with a prevalence in men (45.7%) thrice that in women (15.8%) [
8,
15]. However, recent data on the prevalence of metabolic syndrome in Japanese patients with T2D are limited. This study used a large administrative claims database to evaluate the prevalence of metabolic syndrome in Japanese patients with T2D. The main objective was to assess trends in the prevalence of metabolic syndrome in patients with T2D by sex and BMI. Additionally, we summarized the characteristics, comorbidities, and cardiovascular medication usage of Japanese patients with T2D and metabolic syndrome.
Discussion
This study provides data on the prevalence of metabolic syndrome among patients with T2D using a large administrative claims database in Japan. Approximately 43.0% of Japanese patients with T2D met the full criteria for metabolic syndrome, with differences observed between sex and BMI subgroups. While the BMI ≥ 30 kg/m
2 subgroup had the highest prevalence of metabolic syndrome at 66.1%, the BMI 25 to < 30 kg/m
2 subgroup also had a high prevalence, with a rate more than triple that of the BMI < 25 kg/m
2 subgroup (54.6% versus 17.3%). Although recent data on the prevalence of metabolic syndrome in Japanese patients with T2D are lacking, the current findings are in general agreement with estimates from other countries in the Asia–Pacific region, where higher rates of metabolic syndrome among patients with T2D have been observed [
23,
24].
In the current study, the prevalence of metabolic syndrome in men (46.6%) was nearly double that of women (27.0%). This difference between the sexes was observed in each BMI subgroup but was less pronounced in the highest BMI subgroup, in which prevalence rose to 68.6% in men and 56.3% in women. These data are in accordance with a previous assessment of metabolic disease trends using data collected in the Japanese National Health and Nutrition Survey, which showed steady increases in BMI and HbA1c levels and the prevalence of T2D and obesity/overweight between 1995 and 2019. These increases were much more prominent in men than women [
25]. The findings of the sensitivity analysis showed similar trends to the main analysis. The higher estimates of prevalence in the sensitivity analyses (57.2% overall; 61.5% men; 38.5% women) are in keeping with the use of broader criteria for the definition of metabolic syndrome (i.e., the incorporation of the prescription of antihypertensive and lipid-lowering drugs) compared to the main analysis. The higher prevalence in the sensitivity analysis also suggests that the main analysis may have underestimated the prevalence of metabolic syndrome as a result of the resolution of individual components of the definition, such as hypertension or abnormal lipid profiles, by medical treatment.
The higher prevalence of metabolic syndrome in patients with a BMI > 25 kg/m
2 was not unexpected, as the Japanese clinical guidelines define obesity as BMI ≥ 25 kg/m
2 [
26], and obesity is associated with higher risks of T2D and cardiovascular diseases in Japanese patients [
3,
27]. In addition, visceral fat accumulation in Japanese patients has been shown to increase the risk of metabolic abnormalities (elevated blood pressure, dyslipidemia, and elevated blood glucose levels) and metabolic syndrome, even in the normal-weight BMI range (18.5–22.9 kg/m
2) [
12].
In patients with T2D and metabolic syndrome, the rates of cardiovascular and renal comorbidities and cardiovascular drug usage increased in the higher BMI (BMI ≥ 25 kg/m
2) subgroups compared to the BMI < 25 kg/m
2 subgroup. These findings are in keeping with prior literature indicating that cardiovascular and renal diseases are common in patients with metabolic syndrome and T2D [
1]. These data highlight the need to better manage metabolic syndrome in addition to glycemic control in Japanese patients with T2D, for example, via lifestyle interventions such as diet and physical activity to reduce BMI and/or visceral adiposity and to counter hypertension and dyslipidemia. Reduction of waist circumference via improvement in lifestyle factors has been suggested as a key treatment target to improve metabolic health and reduce adverse outcomes [
28,
29]; however, additional study is required to establish optimal waist circumference cutoffs for risk management by age, sex, and ethnicity [
29].
The JMDC database provided a large, real-world sample population for this study, an important consideration for the analysis of disease prevalence; however, this study had limitations. Since the data were sourced mainly from healthcare insurance associations for company employees and their dependents, patients aged over 75 years are under-represented. Additionally, fewer women than men were included in the study cohort, which is aligned with the reported lower T2D prevalence in women compared to men in Japan [
25]; however, the smaller sample size for women should be taken into consideration when interpreting the data. Finally, some metabolic parameters had missing data, and the potential impact of this on the current estimates of prevalence should also be considered.
Conclusions
Approximately two in five Japanese patients with T2D had metabolic syndrome, accounting for 43.0% of the study cohort, with a higher prevalence in patients with a BMI ≥ 25 kg/m2. In patients with T2D and metabolic syndrome, cardiovascular and renal comorbidities and cardiovascular medication usage were increased in the higher BMI subgroups, underscoring the importance of managing metabolic parameters in addition to glycemic control in Japanese patients with T2D, particularly in those with a BMI ≥ 25 kg/m2. These results also suggest that body weight management in Japanese patients with T2D is important to achieve improved clinical outcomes.
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