This study used data from the KCHS for the years 2009 and 2011 through 2019, and 2021 through 2022 (excluding 2010 and 2020) [18,19]. The KCHS is an annual initiative conducted by trained interviewers through household visits. This self-reporting survey targets approximately 900 adults aged 19 years and older at each of the 255 public health centers nationwide. It covers 18 domains and includes 163 health-related questions. In 2022, a comprehensive survey was conducted involving a total of 227,279 individuals. Out of the 163 survey questions, 18 focused on unmet health care and dental care needs. The analysis included factors such as age, sex, marital status, education, occupation, income status, residence, primary livelihood security recipient, smoking status, alcohol consumption, weekly walks, self-rated health, depression, BMI, and previous diagnoses of diabetes mellitus and hypertension. Data on unmet dental care needs for 2010 and 2020 were unavailable for this study. In total, 2,700,705 participants were included, with 1,229,671 (45.5%) being men (Figure 1).

The KCHS data were anonymized, and the study protocol received approval from the Institutional Review Board of the Korea Disease Control and Prevention Agency. All participants provided informed consent, and the study was conducted in accordance with the principles of the Declaration of Helsinki (approval numbers 2010-02CON-22-P, 2011-05CON04-C, 2012-07CON-01-2C, 2013-06EXP-01-3C, 2014-08EXP-09-​4CA, and 2016-10-01-TA).

The Andersen Health Care Utilization Model is a well-established theoretical framework that systematically analyzes both social and personal factors to explain determinants of health service utilization [20]. According to the model, 3 dynamics—predisposing, enabling, and need variances—determine the consumption of health services, including outpatient and inpatient treatment. Predisposing factors are sociodemographic traits that increase an individual’s demand for health care, such as age, ethnicity, sex, and socioeconomic status. For example, individuals are more likely to seek care if they believe that using health services effectively addresses their illness. Enabling factors encompass community support, availability of health insurance, and family support. The demand for care reflects both one’s actual and perceived need for medical services. We referenced the Andersen Health Care Utilization Model to identify inequalities in access to health services and to determine how various factors contribute to the utilization of these services.

Unmet health care and dental care needs were defined as instances where individuals did not receive the medical or dental services deemed necessary by experts or desired by the patients [4]. Subjective unmet health was analyzed based on the question “Have you ever needed health care (test or treatment) in this year but not received medical treatment?” and subjective unmet dental care was analyzed based on the question “Have you ever needed dental care (test or treatment) in this year but not received medical treatment?” [21].

The survey period was treated as the independent variable and divided into 5 time segments to ensure estimation stability: 2009-2011 (excluding 2010), 2012-2014, 2015-2017, 2018-2019, and 2021-2022. The years 2021 and 2022 were designated as the COVID-19 pandemic period.

The following covariates were considered as predisposing factors: age groups (19-39, 40-59, and ≥60 years), sex, marital status, education level (elementary school or lower, middle school, high school, and college or higher), residence (urban and rural) [22], and occupation (unemployed, blue-collar, and white-collar). Enabling/disabling factors included income status (unknown, <3 million KRW, 3-5 million KRW, and ≥5 million KRW per month; 1 KRW=US $0.00073) and being a basic livelihood security recipient. Need factors included smoking status, alcohol consumption (none, monthly, and weekly), weekly physical activity (rarely, 1-2, 3-4, and ≥5 times per week), subjective health status (bad, normal, and good), depression, previous diagnoses of diabetes mellitus or hypertension (yes or no), and BMI categories (underweight [<18.5 kg/m²], normal [18.5-22.9 kg/m²], overweight [23.0-24.9 kg/m²], and obese [≥25.0 kg/m²]) [23-26].

We investigated overall population characteristics and calculated the weighted prevalence of unmet health care and dental care needs for each subgroup. To obtain national prevalence estimates, we performed a comprehensive sample analysis, accounting for stratification, clustering, and weighting. The methodology for calculating weights was carefully designed to reflect the complex survey design of the KCHS [27]. Weights assigned to each respondent were used to adjust for differences in selection probabilities and to align with the age and sex distribution of the Korean population [27]. The weighting process involved several steps, including the calculation of design weights, poststratification weights, and final weights [27]. A weighted linear regression model was used to determine the trend of unmet health care and dental care needs in the prepandemic and pandemic periods, identifying differences in coefficients between these periods. The prevalence and trends of unmet health care and dental care needs were analyzed accordingly. Finally, prevalence ratios (PRs) were computed to evaluate the interaction term for each risk factor, separately for the prepandemic and pandemic periods [28-30]. This analytical approach allows for interpreting which demographic or risk groups exhibited heightened vulnerability to unmet health care or dental care needs during both the prepandemic and pandemic periods. All statistics are presented as weighted percentages with 95% CIs [31]. Statistical significance was defined as a 2-sided P value of <.05 [32-35]. Statistical analyses were performed using SAS (version 9.4; SAS Institute).

Our study represents the first national analysis of unmet health care and dental care needs in South Korea using long-term, large-scale data from the KCHS. We assessed the prevalence of unmet health care and dental care needs from 2009 to 2022, focusing on trends before and during the COVID-19 pandemic. Notably, the overall prevalence of unmet needs showed a continuous decline over time. Interestingly, although the attrition rate for unmet health care needs decreased significantly during the COVID-19 pandemic, unmet dental care needs remained markedly higher than unmet medical needs. Therefore, it is essential to implement more targeted measures to address and prevent these gaps in dental care.

Numerous studies have investigated unmet health care and dental care needs during the COVID-19 pandemic [36]. These studies explored trends and related factors among Korean adults, such as low income [37], urban residence [21], unmarried status, and being female. Additionally, other research on the relationship between unmet medical needs and the COVID-19 pandemic focused on specific populations, including older adults [38], patients with chronic diseases, those with diabetes mellitus or poor glycemic control [39], community-dwelling older adults [40], and young adults [41]. Several studies also examined unmet medical needs in the general adult population in Austria (N=2000) [42], Canada (N=23,972) [43], and the United States (N=1,483,378) [44]. These studies found that older adults, inactive individuals, and retirees were particularly susceptible to experiencing unmet medical needs [42]. Conversely, other research studies indicated that younger individuals are more vulnerable to unmet medical care needs [43,45]. Identified risk factors also include having a chronic disease, being an immigrant [43], and being female [45]. However, most of these studies were limited to short-term analyses, small or specific target populations, and data from either before or during the pandemic. By contrast, our study offers comprehensive insights into risk factors and trends for unmet health care and dental care needs over the years 2009 to 2019 (before the pandemic) and 2021 to 2022 (during the pandemic) using a substantial data set of 2.7 million individuals.

The prevalence of unmet health care and dental care needs may have decreased due to the economic relief provided by the medical insurance system, increased accessibility, and reduced waiting times resulting from the growth in the number of hospitals and clinics. However, the slower rate of decline in unmet needs could also be partially attributed to patients’ reluctance to visit hospitals or clinics due to concerns about potential infection [13,46]. Many experts emphasized that the decrease in hospital visits was not due to a reduction in the number of patients, but rather to anxiety, concerns about infection, and executive orders to close hospitals [4,13].

Significant demographic and social variables have been identified in individuals with a high prevalence of unmet health care needs. Notably, these individuals are often in their 40s, predominantly female, unmarried, with lower income brackets, and minimal levels of education. Blue-collar workers, in particular, are more likely to experience injuries during labor and see a more rapid decline in physical ability as they age. Female blue-collar workers, in particular, reportedly have higher rates of chronic diseases, nontreatment, and poor health behaviors [47]. Additionally, the high unmet health care needs among those with low income, especially basic livelihood security recipients, are largely attributed to the economic burden associated with medical services. Individuals with a low level of education often experience a high rate of unmet health care needs, which is associated with lower income, poor health conditions, and high smoking rates. Similarly, people aged 40-59 years with high working hours and those living in rural areas with relatively low access to medical care are significantly influenced by time burdens, which appear to contribute to unmet health care needs.

The relationship between lifestyle choices and unmet health care needs is evident. Smokers, individuals who rarely exercise, those with poor subjective health, and those who are underweight often experience unmet needs, despite receiving medical services, due to their higher use of health care. Additionally, poor mental health and low self-esteem, including depression, are known to adversely affect unmet medical needs [48]. Unmet health care needs are particularly high among unmarried individuals and women, who are more vulnerable to mental health problems [49]. While the risk factors for unmet dental needs are similar to those for unmet medical needs, unmet dental care needs are notably higher among patients with diabetes mellitus. This may be due to the particularly adverse effects of diabetes on oral health, leading to greater dental care needs [50].

In summary, unmet health care needs were found to be high in groups with significant medical demands and economic, time, and psychological burdens. The β_diff analysis revealed that, after the COVID-19 pandemic, individuals who are older, unemployed, have low income, poor subjective health, low weight, high blood pressure, diabetes, urban residents, and those who smoke or consume alcohol were particularly vulnerable. Groups with high health care demands, such as those with poor subjective health, low weight, high blood pressure, and diabetes, as well as those with weak social or economic foundations (older adults, unemployed, and low income), were more affected by COVID-19. Urban areas also experienced greater changes due to higher population densities and stricter infectious disease regulations [51]. The decrease in dental care needs during the pandemic is attributed to COVID-19’s respiratory transmission, which led to reluctance to visit dentists due to the need to remove masks.

This study has several limitations. First, unmet medical care needs were defined based on patients’ subjective judgments, which might lead to discrepancies with actual needs. Second, values such as health level and BMI were self-reported, although self-reported BMI is generally reliable. Third, data from 2010 and 2020 were excluded due to the absence of questions regarding unmet health care needs, which may affect trend analyses for the COVID-19 pandemic period. Finally, the study focused solely on Korean adults, which may limit the generalizability of the findings to global trends.

This long-term, representative, population-based study shows that while the prevalence of unmet health care needs has generally declined, there was a noticeable decrease during the COVID-19 pandemic. Addressing this issue requires implementing more detailed measures to prevent the emergence of unmet medical and dental care needs.