This study investigated how PCDMP affects individuals' health outcomes, specifically, their HbA1c levels. As described earlier, the PCDMP aims to increase patient acceptance and establish a chronic disease management system in local clinics [11]. Additionally, we utilized HbA1c levels > 6.5% as a high HbA1c indicator [17]. To evaluate the PCDMP as a well-established program and progress to become an official program of the nation, we should investigate whether participating in the PCDMP is helpful for individuals living in such residential areas in terms of HbA1c. For instance, many studies have explored the effect of a PCDMP on the risk of complications and managing hypertension in hypertension patients in South Korea [18, 19] and concluded that the program had positive effects on the health of hypertension patients.
This study, on the other hand, examined the effects of participating in the PCDMP on HbA1c using mixed-effects logistic regression. The main findings of this study are as follows: First, people living in areas with low PCDMP participation have odds of exhibiting high HbA1c, which is 1.40 times greater than that of residents in areas with high PCDMP participation. Second, the likelihood of having high HbA1c was significantly greater in those living in areas with low PCDMP participation. In other words, living in areas with a low PCDMP increases the risk of exhibiting high HbA1c. Our findings are similar to those of previous studies investigating the effects of participating in PCDMP on the health behaviors of hypertension patients [17, 18]. One of the early studies on the effect of the PCDMP on the risk of complications in patients with hypertension in Korea found that the hazard ratio was significantly lower for patients participating in the PCDMP than for patients not participating in the program for all 4 complications—hypertension, myocardial infarction, stroke, chronic kidney disease, and heart failure [17].
Globally, several studies have explored the positive impact of chronic disease management programs in primary care on diabetes management [19, 20]. However, to the best of our knowledge, this is the first study to examine the association between regional PCDMP participation and individual HbA1c levels in nondiabetic individuals utilizing data from local clinics’ PCDMP participation and the KNHANES containing individual health information. Our study is distinguished from early findings in that the regional covariates were adjusted with a multilevel approach using mixed-effects considering the clustering effects of regions in the datasets. Furthermore, external validity would be high when a large sample is included. Our study's significant conclusions included the possibility that PCDMP may help individuals who are not diagnosed with diabetes by doctors not to get diabetes, which may lead to a decreased possibility of reduced healthcare expenses [21]. Consequently, the PCDMP might be an affordable diabetes management approach. On the other hand, research has shown that the PCDMP's diabetes education program and required testing in local healthcare facilities have no appreciable impact on diabetic patients' ability to maintain a healthy blood sugar level, an alternative diabetes index [22].
Nonetheless, this study has a few limitations. First, the KNHANES data used in the study were secondary, and it was not feasible to perform a time-series analysis to monitor changes in individual health status as the survey items differed annually. A second constraint was that residential areas were divided into only 17 regions in Korea when we calculated the participation of the PCDMP. In addition, the current PCDMP is a pilot program run by the Korean government; thus, if it becomes an official program, the procedures and details of the program are subject to change. Third, individuals’ HbA1c levels are divided into two categories, \(\ge\) 6.5% and < 6.5%, where information may be lost about individuals with HbA1c levels of nearly 6.5%. Additionally, diagnosing diabetes is not solely based on HbA1c levels; rather, other tests, including screening tests and glycemia tests, may be used; moreover, there are no perfect guidelines for diabetes diagnosis [23–25]. Finally, in statistical analysis, few regional covariates are linear combinations of other variables, which leads to unreliable and unstable estimates of regression coefficients [26].