This study aimed to examine the association between depressive symptoms, SESs, and medical care utilization in a South Korean older adult population. Our results indicate that there are statistically meaningful differences in medical care utilization among elderly individuals with chronic diseases. Compared to patients with good mental health, patients with depressive symptoms had a higher frequency of inpatient hospitalization (OR = 1.49, 95% CI = 1.13–1.97). This result represents two effects of depressive symptoms on health. First, depressive symptoms negatively affected health condition. In previous studies, depressive symptoms were associated with increased vascular disease and risk factors for vascular disease development [2]. Many studies have stated that suffering depressive symptoms is related with a meaningful increase in the chance of coronary heart diseases [19]. Another study revealed that the chance of developing metabolic syndrome was about 2.5 times higher that observed patients with depressive symptoms [20]. One of the systematic review of some longitudinal studies stated that patient with depressive symptoms were at a higher risk of metabolic disease relative to people without depressive symptoms [21, 22]. Moreover, one of a large population study found that older adults with depressive symptoms showed meaningfully increased risk of diagnosed chronic diseases such as hypertension, after adjusting for socioeconomic and demographic variables and comorbid chronic diseases, than did those without depressive symptoms [23]. Second, patients with depressive symptoms may undergo worsening of chronic diseases [12]. In this study, patients with depressive symptoms visited outpatient clinics less frequently than did those without depressive symptoms. This may disrupt the continuity of disease care and worsen disease conditions [24]. Therefore, patients with depressive symptoms tend to be hospitalized more often than those without depressive symptoms.
There were some significant findings from the analysis of subgroups according to independent variables. First, compared with men without depressive symptoms, those with depressive symptoms usually had fewer outpatient visits and were hospitalized more. However, women did not show this pattern. Men with depressive symptoms tend to neglect their own chronic disease, which results in worsening of condition and hospitalization. Second, in the experience of inpatient hospitalization, those covered by the NHI experienced more inpatient hospitalizations than those supported by medical aid with depressive symptoms. This result may imply a health care expenditure issue. Although medical aid covers almost of hospital inpatient fees, patients with depressive symptoms who had low property or earned low income could not be capable of expenditure for inpatient hospitalization except for fees. Therefore, they had fewer inpatient hospitalizations than that of the patients covered by NHI. Regarding other variables, such as ADL, patients with depressive symptoms and ADL limitation experienced more inpatient hospitalizations than did those without ADL limitation. This result implies that limited ADL may affect patients with depressive symptoms more than it does mentally healthy patients. A previous study also showed that ADL limitation was associated with hospitalization [25]. In South Korea, approximately 500 thousand patients were hospitalized in nursing hospitals in 2019, and it is difficult to estimate how many patients used nursing home facilities because of their inability to perform daily activities [26]. Therefore, limitation of ADL may lead to increased inpatient hospitalization and health care burden.
In the analysis of each chronic disease type, the risk of hospitalization seemed to increase with each chronic disease. Patients with chronic disease showed an increased OR for inpatient hospitalization, although the difference was not statistically significant. However, patients with hypertension and diabetes showed significantly increased values (OR = 2.77, 95% CI = 1.45 5.30). On the other hand, these patients showed a relatively lower OR for outpatient visits, but this was not statistically significant. These results imply that depressive symptoms may negatively affect primary care for chronic diseases, especially hypertension and diabetes. Depressive symptoms results in decreased primary care visits and may worsen chronic diseases [27]. This may cause an increase in inpatient hospitalization [22].
Unfortunately, there were some limitations of this study. First, as this was a cross-sectional study, causality could not be established. Therefore, the relationships found in this study should be confirmed using longitudinal studies or other research designs. Second, this study might have recall bias issue as we used self-stated information for variables. This study may have had a selection bias because of the potential reluctance of participants in responding honestly regarding their depressive symptoms and health status. Third, this study did not show any differences based on sex, which was simply included as a part of the independent variables.
Despite these limitations, the study has some advantages in terms of its nationally representative large sample size and handling of the aspects relevant to medical care utilization, especially compared to former studies. A lot of studies have examined the associations between health status of older adults and their medical care usage [2, 22, 27]. This study, however, considered not only depressive symptoms but also took into account common chronic diseases, such as diabetes and hypertension, which may affect the medical care use of this population. Unfortunately, in South Korea, there is insufficient governmental support or incentives for patients who suffer from depressive symptoms. There are policies aimed at people suffering from chronic diseases or depressive symptoms. However, we did not find any policies that targeted patients with both depressive symptoms and chronic diseases. Our results showed that depressive symptoms may be related to chronic disease management, and the government needs to pay close attention to older adults with such complex health conditions.