Diabetes control in public assistance recipients and free/low-cost medical care program beneficiaries in Japan: a retrospective cross-sectional study

Introduction

In Japan, approximately 10 million patients have diabetes, with approximately 16 000 starting dialysis due to diabetic end-stage renal disease annually.1 16% of hospitalised patients have diabetes, making appropriate management and prevention of disease exacerbation considerable public health challenges.2 Diabetes is a multifactorial disease, with obesity, physical inactivity and smoking being the most well-known epidemiological risk factors. However, it has become evident that many social determinants of health contribute to diabetes.3 Hill-Briggs et al reported factors such as education, income, occupation, housing, food insecurity, healthcare affordability and social capital as social determinants of health for diabetes, with income being an important determinant.3 Diabetes prevalence increases among individuals with low income, leading to poor diabetes control, increased frequency of microvascular and cardiovascular complications and shortened lifespan.3 4

Excessive out-of-pocket medical expenses lead to treatment interruptions, worsening treatment outcomes and increased use of emergency medical care.5 According to Tanaka et al, outpatient medical expenses for diabetes in Japan were ¥390 000 annually.6 As the average out-of-pocket burden under public health insurance (PHI) in Japan is 30%, this amounts to an average of ¥13 000 per month.6 Due to the high cost of antidiabetic medications such as insulin, the financial burden is higher for patients with diabetes than for those without, exacerbating economic strain.5–7 Consequently, excessive out-of-pocket expenses worsen treatment interruptions and compliance among patients with diabetes.5 7 8 Ngo-Metzger et al reported that an increase in out-of-pocket medical expenses is associated with a 1.37-fold increase in the OR for worse adherence to diabetes treatment.9 Therefore, outpatient treatment for diabetes poses a considerable economic burden on individuals with low income, raising concerns about worsening treatment outcomes.5 7 10

In Japan, social security systems such as public assistance and free/low-cost medical care (FLCMC) programmes have been implemented to alleviate the burden of out-of-pocket medical payments for individuals with low income. Public assistance is a public system that provides comprehensive economic support, including housing, meals and medical care, to ensure the minimum necessary standard of living. The Ministry of Health, Labour and Welfare has set the minimum living expenses required for a minimum standard of living, which serves as the poverty line in Japan. Eligibility for public assistance is determined by a rigorous examination conducted by local governments for households whose incomes fall below the poverty line. As of 2022, 2.04 million recipients of public assistance (PARs) were recorded, with a recipient rate of 1.63%. Among the recipients, the proportion of individuals aged ≥65 years is 55%.

Furthermore, the FLCMC programme provides social security for individuals with low income by offering free or reduced out-of-pocket payments for approximately 7.5 million people.11 Households with incomes approximately below 1.5 times the poverty line are eligible, and eligibility for the programme is determined at the discretion of medical institutions. For patients who do not receive public assistance but have difficulty paying medical expenses, this programme serves as a valuable system to alleviate the economic burden of accessing medical care. However, compared with public assistance, the FLCMC programme only reduces out-of-pocket payments at medical institutions and does not provide support for living expenses. The facilities eligible for the FLCMC programme are medical institutions licensed under the Social Welfare Act, with only 673 medical institutions being licensed among Japan’s 180 000 medical institutions in 2018.

Some studies reported high prevalence rates of diabetes and diabetic complications among PARs.4 12 According to Sengoku et al, the prevalence of diabetes among outpatient PARs was 7.5%, compared with 4.1% among the PHI beneficiaries.12 A survey by the Ministry of Health, Labour and Welfare found that PARs are more likely to be obese, have lesser regular exercise habits and have fewer regular dietary habits, suggesting that adequate support is needed for proper adherence to diabetes treatment.13 However, reports on diabetes control among PARs are lacking, and the status of treatment adherence among PARs has not been investigated.

Regarding FLCMC programme beneficiaries, no study has examined the prevalence of diabetes or diabetic complications due to the limited availability of facilities. The study by Ono et al is the only one that has investigated diabetes control among FLCMC programme beneficiaries.14 In their study, the glycated haemoglobin (HbA1c) levels of drug-treated patients with diabetes were 7.5%, significantly higher in FLCMC programme beneficiaries than in PHI beneficiaries (7.0%).

Despite the importance of diabetes control for preventing microvascular and macrovascular complications, limited studies have been published on diabetes control among PARs and FLCMC programme beneficiaries.15 Furthermore, diabetes control has not been compared between PARs, who receive comprehensive public economic support, including living expenses and FLCMC programme beneficiaries, who receive reduced out-of-pocket payments only at medical institutions, despite both being low-income groups.

In clinical settings, healthcare professionals are reluctant to inquire about a patient’s economic status, as it is considered sensitive information.9 16 However, in Japan, the utilisation status of social security systems is valuable information for understanding a patient’s economic status, and this information can be easily obtained in clinical settings. If it became apparent that blood glucose control is poor among PARs and FLCMC programme beneficiaries, information on the utilisation of these systems could predict the state of treatment adherence and determine whether patients require more support, thereby becoming clinically useful information. Furthermore, examining the difference in treatment adherence regarding diabetes between PARs and FLCMC programme beneficiaries could be useful for considering the design of social security systems for individuals with low income.

Therefore, this study aimed to examine the state of diabetes control among PARs and FLCMC programme beneficiaries by investigating the association between the type of medical insurance and HbA1c levels in patients with diabetes.

Materials and methods

Results

The patients were predominantly male (61.7%) and aged ≥65 years (58.4%; table 1). HbA1c levels of ≥9% and ≥7% were observed in 9.4% and 62.8% of the patients, respectively. Regarding medical insurance, PARs and FLCMC programme beneficiaries accounted for 28.4% and 8.9% of the patients, respectively.

A comparison of the three groups showed that the mean age of FLCMC programme beneficiaries was significantly lower than that of PHI-only beneficiaries (p=0.0003) and that of PARs (p=0.0005; table 2). Moreover, the average HbA1c levels were significantly higher in FLCMC programme beneficiaries (p=0.0012) and PARs (p=0.0061) than in PHI-only beneficiaries. The proportion of individuals with HbA1c levels of ≥9% was significantly higher in FLCMC programme beneficiaries (p=0.0001) and PARs (p<0.0001) than in PHI-only beneficiaries. Additionally, the proportion of individuals with HbA1c levels of ≥7% was significantly higher in FLCMC programme beneficiaries (p=0.003) than in PHI-only beneficiaries.

In multivariate analysis, the adjusted ORs for HbA1c levels of ≥9% using PHI-only beneficiaries as the reference group were significantly higher among individuals aged ˂65 years who were FLCMC programme beneficiaries (OR=5.37, 95% CI: 2.23 to 12.82) and PARs (OR=5.97, 95% CI: 2.91 to 12.74; table 3). The adjusted OR for HbA1c levels of ≥7%, using PHI-only beneficiaries only as the reference group, was significantly higher among individuals aged ˂65 years who were FLCMC programme beneficiaries (OR=3.82, 95% CI: 1.65 to 10.43). However, no significant association was observed in individuals aged ≥65 years.

When using PARs as the reference group, no significant association was found for HbA1c levels of ≥9% (table 4). The adjusted OR for HbA1c levels of ≥7%, using PARs as the reference group, was significantly higher among FLCMC programme beneficiaries (OR=2.57, 95% CI: 1.02 to 7.44). However, no significant association was observed in individuals aged ≥65 years.

Discussion

To the best of our knowledge, this study is the first in Japan to elucidate the state of diabetes control among PARs and FLCMC programme beneficiaries. Consequently, two points became apparent. First, among adults aged ˂65 years, PARs and FLCMC programme beneficiaries had significantly higher HbA1c levels than PHI-only beneficiaries. Second, among low-income groups, HbA1c levels were higher in FLCMC programme beneficiaries than in PARs.

The finding that HbA1c levels were higher in PARs and FLCMC programme beneficiaries, who are individuals with low income, aligns with the results of many previous studies indicating poor diabetes control among this population.18 According to the meta-analysis by Bijlsma-Rutte et al, the mean HbA1c level was increased by 0.20% among individuals with low income.18 The mechanisms behind the higher prevalence of diabetes and poorer diabetes control among individuals with low income include difficulties in maintaining a balanced diet for diabetes prevention and lower levels of regular physical activity.19 Additionally, psychological and social stress due to economic hardship may influence stress hormones related to blood glucose levels and insulin sensitivity.19 20 Therefore, we hypothesised that poor diabetes control among PARs and FLCMC programme beneficiaries may be attributed to similar mechanisms. However, it should be noted that the second most common reason for receiving public assistance is illness. Therefore, some recipients may be impoverished due to severe complications of diabetes, potentially contributing to the observed higher HbA1c levels.

Age-stratified analysis revealed that only adults aged ˂65 years showed higher HbA1c levels among PARs and FLCMC programme beneficiaries, which is consistent with previous research. Branfield et al reported that patients with diabetes living in low-income areas had a 0.21% higher HbA1c level among those aged ˂65 years compared with those living in high-income areas, with a 0.11% higher level among those aged ≥65 years, indicating a greater disparity in younger individuals.21 The impact of socioeconomic status on health tends to diminish or remain unchanged regarding mortality with ageing.22 This may be attributed to increased support from social security systems, reduced social stratification due to retirement and the stronger health effects of biological risk factors in older age.22 Furthermore, the relatively healthier survival of older individuals may contribute to the attenuation of disparities.22

The results of this study suggest that the findings regarding diabetes control among low-income individuals aged ˂65 years align with those of previous research on the relationship between income and glycaemic control. In Japan, information on the utilisation of social security systems is valuable for understanding patients’ economic status and can be easily obtained in clinical settings. Therefore, information on the utilisation of public assistance or the FLCMC programme could serve as predictive factors for identifying patients in need of additional support for improving blood glucose control.8

The finding that FLCMC programme beneficiaries have poorer diabetes control than PARs highlights potential differences in adherence to diabetes treatment and the influence of psychological and social stress between the two groups. Economic burdens associated with out-of-pocket medical payments and diabetes treatment may exacerbate cost-related medication non-adherence and worsen diabetes control.9 FLCMC programme beneficiaries may avoid prescriptions for insulin or expensive diabetes medications due to the financial burden, leading to treatment interruptions.11 Furthermore, despite their economic hardship, FLCMC programme beneficiaries do not receive comprehensive public support for living expenses, such as housing, food and education, which may lead to increased psychological and social stress.23 Additionally, FLCMC programme beneficiaries may experience social isolation, such as limited opportunities to meet friends or acquaintances, which could further worsen adherence to diabetes care and accumulate psychological and social stress, ultimately impeding diabetes control.20 24 Therefore, it is necessary to provide comprehensive economic and psychosocial support, including reducing out-of-pocket payments at pharmacies and providing living allowances, to FLCMC programme beneficiaries, who have poorer blood glucose control than PARs, who receive comprehensive support.

Public assistance is the most important means of alleviating the adverse health effects of socioeconomic disadvantages.25 However, a systematic review by Shahidi et al investigating the health improvement effects of public assistance reported that PARs are more likely to experience depression and obesity, and despite the provision of medical and living expense support, there is no improvement in their health status.25 High levels of psychological and social stress among PARs may contribute to worsening diabetes control, indicating that public assistance alone is insufficient to eliminate health disparities, and additional support for individuals with low income is needed.23