Measuring the Burden of Disease in Korea Using Disability-Adjusted Life Years (2008–2020)

Measuring the health status and monitoring its characteristics and trends over time are fundamental to improving the health of a population.1 Policymakers in the health sector rely on this data to make informed decisions and establish suitable priorities. Therefore, valid, reliable, and comparable measures of health status of populations and their subgroups are critical components of the evidence base used for drafting health policy.2 Hence, it is essential to obtain information on the health status of a population, commonly known as the “burden of disease.”3 The disease burden of the population can be assessed using a variety of indicators,3 one of which is the disability-adjusted life year (DALY). DALY provides a comprehensive measure of both mortality and non-fatal health outcomes.4 The DALY measurement methodology, developed by the influential Global Burden of Disease (GBD) projects initiated in the early 1990s, has been adapted to fit the Korean context and efforts have been made to calculate the burden of disease of Koreans using domestic data sources. The Korean National Burden of Disease (KNBD) study was first conducted in 2002 and continues to this day.5

In the KNBD study, disability weights (DWs) that can more appropriately reflect social preferences for diseases in Korea were calculated and applied.6 In addition, efforts are being made to improve methods to address the limitations associated with GBD study utilization. These include use of multiple assumptions, methodological choices required to integrate various information, and timeliness of data inputs into the GBD study.7 Moreover, a significant advantage lies in the easy accessibility and utilization of the National Health Insurance Service (NHIS) claims data, which serves as the primary source for calculating years lived with disability (YLDs). The NHIS claims data includes all information on medical service utilization (excluding non-insured service) by patients who have visited medical institutions. This wide-ranging dataset enables the generalization of analysis results. Consequently, it becomes relatively easier to calculate input parameters such as incidences and prevalences that are valid, reliable, and representative of the population’s health.5 The most recent publication of the KNBD study results was in 2021, which encompassed the measurement of the disease burden of Koreans from 2008 to 2018.8 Subsequently, updating the measurement results is necessary to ensure their relevance and accuracy.

Meanwhile, the spread and prolonged coronavirus disease 2019 (COVID-19) pandemic, that started in 2020, caused immense human suffering; its consequences extend beyond immediate health impacts, severely affecting daily life and the overall quality of life of people worldwide.9 The COVID-19 pandemic and its countermeasures have had a significant impact on healthcare utilization patterns and outbreaks of infectious diseases, including reduced access to prevention and treatment services.10 To date, no comprehensive study have been conducted to ascertain the overall impact of COVID-19 on the burden of disease for all diseases and injuries, nor has the trend of DALYs according to socioeconomic levels been thoroughly examined. Furthermore, the emergence of COVID-19 as a novel disease necessitates the application of updated DWs when calculating disease burden, as the previously calculated weights may no longer be applicable. Hence, it is crucial to incorporate revised and up-to-date DWs when assessing the disease burden in 2020 and subsequent years.

Therefore, this study was conducted to understand the changes in disease burden and national health levels among Koreans by identifying its trend from 2008 to 2020 and evaluating the differences by region and income level.

The burden of disease on Koreans as measured using DALY increased by 19.8% from 2008 to 2019; however, in 2020, when COVID-19 first emerged, it decreased by 4.7% compared with the previous year, resulting in an overall increase of 13.8% over the past 12 years. Meanwhile, until 2019, before the outbreak of COVID-19, YLLs decreased and YLDs increased. However, in 2020, the opposite was observed. This shift can be attributed to the reduced accessibility of medical services due to the COVID-19 pandemic, leading to a decline in inpatient and outpatient medical usage.19 Therefore, when analyzing the overall trend and its characteristics, it is important to interpret the results of 2020 while considering the influence of COVID-19. Furthermore, continuous monitoring of the disease burden and identifying changes in the health status of Koreans remain crucial. The increase in DALYs until 2019 was primarily driven by the increase in YLDs as opposed to the decrease in YLLs. This pattern was consistent across both men and women.

The increase in YLDs may be attributed to the reduction in the burden of medical expenses and the improvements of medical accessibility following the continuous implementation of policy on expanding health insurance coverage. In 2020, the NHI coverage rate was 65.3%.20 When benefits are added or the number of beneficiaries is expanded, and the out-of-pocket burden of existing benefit items is lowered, the use of medical service tends to increase. Thus, the incidences and prevalences, which are the basis of YLDs calculations, may have increased. In contrast, YLLs gradually decreased, which is primarily attributed to the improvement in overall living conditions and advancements in medical technology that have led to reduced mortality rates from diseases and non-disease-related causes.21

Until 2016, DALYs in women were higher than that in men; however, this was reversed in 2017 and the sex-specific gap in disease burden widened in 2020, when COVID-19 first emerged. Similar to the contribution of increased YLDs to the overall increase in DALYs for the population, the shift where DALYs in men surpassed those in women can be attributed to the higher rate of increase in YLDs in men (24.4%) compared with those in women (12.9%). To determine the reason for the increase in YLDs in men, we additionally analyzed the increase rate in YLDs by cause in men and women, respectively (Supplementary Table 1). We examined the increase rate in 2020 compared with 2008 for the top leading causes in 2020 for each sex. Our analysis revealed that the rate of increase in YLDs in men was higher than that of women in diseases such as ischemic stroke, ischemic heart disease, and major depressive disorder, which have a DW of 0.5 or more, as well as diabetes and low back pain, which rank first and second in YLDs. Therefore, the increase in YLDs for these diseases in men may have contributed to the reversal of DALYs by sex. Nevertheless, YLDs in women remains 1.04 times higher than that in men. Similar to the West, women use more medical services than men. These factors include not only the harsh environments due to physiological changes such as pregnancy, childbirth, and menopause, but also the traditional roles such as housework and responsibility in caring for the physical and mental health of the family members at home.22 Hence, it is necessary to continue to monitor changes in DALYs by sex. Furthermore, for diseases with a high increase in YLDs in men, it may be meaningful to conduct research to examine the causes in relation to health risk factors.

When examining the burden of disease in 2020, diabetes mellitus emerged at the top, accounting for 10.1% of the total burden of disease. It also ranked first in both men and women, with a higher burden observed in men compared with women. Diabetes mellitus has become a prominent disease among modern populations, primarily attributed to westernized dietary habits and sedentary lifestyles. Therefore, it is imperative to proactively address this issue at the national level through active management and preventive measures. As of 2020, the population with diabetes in Korea reached 5.7 million (5.26 million over the age of 30), with an estimated 14.97 million individuals in the pre-diabetes stage.23 Recently, patients with obesity and diabetes are increasing, affecting not only the elderly but also the younger population due to excessive caloric intake and a lack of physical activity. Since the rate of diabetes awareness, treatment, and control in young patients is considerably low, and lifestyle management is passive,23 this may potentially lead to serious health consequences, including the development of complications. Therefore, it is essential to take preemptive preventive measures. Moreover, there is an urgent need for national responses such as establishing an integrated diabetes care plan, promoting education and counselling centered on primary medical institutions, establishing infrastructure, and preparing relevant policies. Ultimately, to prevent or delay progression to diabetes and development of its complications in individuals with ‘pre-diabetes,’ countermeasures such as the identification of high-risk groups through the introduction of additional criteria24 and development of appropriate management guidelines for early lifestyle interventions need to be promoted.

We identified diseases that ranked in the top 20 burdens of disease from 2008 to 2020. Among these, the DALYs due to Alzheimer’s disease and other dementias increased the most steeply. As Korea is on the verge of becoming a super-aged society, the number of patients with dementia, a representative aging disease, is rapidly increasing, and the social cost is expected to increase accordingly. The number of patients who received treatments for dementia in 2019 was 799,000 (4 times that in 2009), and the number of patients with mild cognitive impairment was 276,000 (19 times that in 2009).25 The National Responsibility Policy for Dementia Care was implemented to solve the problem of dementia; however, many policies emphasized the welfare aspect, and it was pointed out that the integration and organic connection between medical and care services was insufficient.26 Considering the rapidly increasing demand for management in patients with dementia, it is necessary to emphasize the expansion and functional strength of public medical institutions.27 In particular, since the community management rate is low in non-metropolitan areas,28 where population aging is severe, it is necessary to strengthen the capacity to respond to the rapid increase in dementia through sufficient expansion and utilization of public medical institutions. In addition, since cardiovascular risk factors including diabetes and hypertension are related to the risk of dementia,29 efforts are needed to effectively manage these factors to reduce the risk of cognitive impairment and dementia.

A significant increase in DALYs due to periodontal oral disease was also observed, which reflects the effect of the health insurance coverage expansion policy for dental services implemented in July 2013. The expansion of coverage to include scaling may have improved dental care access by lowering patient out-of-pocket costs and increased preventive dental care utilization.30, 31, 32, 33 The disease burden associated with BPH also showed a notable increase. Age has been identified as an important risk factor for BPH,34 and higher treatment rates among the elderly35 may contribute to this trend. However, concerns have been raised regarding unfair prescription and claims for BPH medications to treat hair loss in relation to the increase in patients with BPH. Finasteride and dutasteride are used for hair loss treatment after dosage adjustment.36, 37 Notably, while BPH is covered by health insurance, hair loss is not and considered as non-insured. Consequently, there is a concern that patients aiming to alleviate their financial burden, may be prescribed drugs for BPH, which are covered by insurance, and use them for hair loss treatment. This may have contributed to the rapid increase in the disease burden associated with BPH. The disease burden for major depressive disorders and phobic anxiety disorder also showed a significant increase over the past 12 years, and continued to increase between 2019 and 2020. This is also confirmed from the results of an analysis of treatment trends, which showed that patients with depression increased by 35.1% and patients with anxiety disorder by 32.3% from 2017 to 2021.38 In 2021, a significant increase in the number of patients was observed among individuals in their 20s, with a 127.1% increase in depression and an 86.8% increase in anxiety disorders. Furthermore, the prevalence of these conditions was higher among female patients compared with male patients.38 Factors such as the intense competition for university admission,39 job-seeking stress, and work stress,40, 41 which are unavoidable in a highly competitive society, and the impact of the COVID-19 pandemic,42 may have contributed to mental health problems.

Meanwhile, the DALYs showed an increasing trend for chronic lower respiratory diseases (excluding asthma) and osteoarthritis from 2008 to 2019, but decreased by 37.7% and 35.2%, respectively, compared with 2020 during the COVID-19 pandemic. The decline in disease burden for these causes was substantial to the extent that the overall burden declined from 2008 to 2020. Among the top diseases with high DALYs in 2020, these diseases appear to have been most impacted by the decrease in medical utilization due to COVID-19. As of 2020, diabetes mellitus and low back pain, remained the causes with the highest disease burden among Koreans, and both causes exhibited a consistent increase even between 2019 and 2020. Over the span of 12 years, the burden for both diseases increased by more than 50%. Notably, diabetes mellitus increased by nearly 20% in disease burden from 2019 to 2020, raising awareness of the importance and necessity of management.

Asthma has experienced a substantial decline in disease burden, dropping from the second position in 2008 to the twenty-seventh position in 2020, reflecting a significant decrease of 76.7%. An analysis conducted by the Health Insurance Review and Assessment service also confirmed a 19.8% decrease in the number of patients with asthma from 2010 to 2014.43 The exact reasons behind this decline have not been fully elucidated; however, one possible factor could be the implementation of a mild disease differential copayment policy in 2011, which aimed to improve the efficiency of the medical delivery system. This policy introduced varying coinsurance rates for prescription drugs when patients seek healthcare for a minor illness.44 While further investigations are warranted, it is important to consider the possibility that changes in disease coding or diagnosis practices, such as assigning alternative diagnoses instead of asthma in a secondary or tertiary hospitals, could have contributed to the reduction in the burden on patients. Moreover, the sharp decrease in asthma inpatients during the COVID-19 pandemic may have also played a role.45

To assess the health status of different regions, this study analyzed DALYs, YLLs, and YLDs across 250 regions. The findings revealed notable health inequalities between regions, with a lower burden of disease observed in and around metropolitan cities. These health inequalities may be differences in health behaviors and health check-up rates by region. Previous studies have reported that residents living in rural areas have higher metabolic risk46 and adult obesity rates47 compared with those of residents living in urban areas in Korea. Additionally, it has been found that the general health check-up rate is higher in small and medium-sized cities and large cities compared with that of rural areas.48 Because individuals who participate in regular health checkups have fewer risk factors for cardiovascular diseases than those who do not,49 these characteristics are considered to be associated with regional health disparities. In addition, health disparities depending on residential area are caused by differences in social structural factors that are difficult to overcome at the individual level, and among them, accessibility to health care facilities needs to be considered. Geographical access to health care plays a crucial role in increasing the utilization of preventive health care services, and consequently, improving health outcomes.50, 51 In Korea, medical facilities are predominantly concentrated in metropolitan areas and large cities52 and the concentration of population in large cities further exacerbates the concentration of healthcare resources in these areas, resulting in disparities in medical utilization. Because insufficient primary care can contribute to poor control of chronic diseases and quality of life,53 we suggest that a national approach to ensure an even distribution of medical institutions capable of providing primary care and early screening is needed. Considering these possibilities, future studies could explore the relationship between regional characteristics and YLLs and YLDs measurements from this study to identify geographical health risks. This approach would provide valuable information for developing region-specific policies and, ultimately, reducing health disparities between different regions.

The analysis of DALY differences across income quintiles overtime revealed a widening disparity in health levels based on income. Specifically, there was a 1.40-fold differences in disease burden between the lowest-income quantile (Q1) and the highest-income quantile (Q5). Of this difference, 1.27 times can be attributed to the gap between Q1 and Q2, highlighting the urgent need for targeted health management for individuals in the lowest income bracket. Although the disease burden decreased for all income quintiles from 2019 to 2020, the reduction rate was the lowest for Q1. To gain a better understanding of disease burden by income level, further research is necessary to analyze specific factors such as YLLs, YLDs, sex differences, and explore diseases with higher burden among each income level. By conducting more detailed analyses in future studies, it may be possible to gain insights into the specific health challenges faced by individuals in different income groups and design interventions to address the diseases that significantly contribute to the disease burden within each income category.

This study provides valuable insights into the burden of disease in Korea, considering various factors such as regional disparities and income inequality. However, some limitations need to be acknowledged. First, we did not include the calculation of DALY for COVID-19, which is an important public health issue. Future research should incorporate the disease burden of infectious diseases, including COVID-19, to provide a comprehensive assessment. Second, the estimation of YLDs may have underestimated the burden of disease that relies on over-the-counter drugs or has low medical utilization rates. Further research is needed to improve the methodology for calculating YLDs in such cases. Additionally, age standardization was not applied in calculating disease burden by region, which limits the comparability between regions. Further studies should consider age standardization to enhance regional comparability. Lastly, because this study measured DALYs based on claims data, only data of those who used medical care were included in the assessment of disease burden. As a result, YLDs decreased and YLLs increased in 2020. Changes in the disease burden of periodontal disease, asthma, and BPH over the past 12 years can also be interpreted in a similar context. As this methodology included claims data, DALYs in 2020 were measured using data reflecting changes that occurred due to COVID-19. In order to overcome these methodological limitations, follow-up studies will need to be conducted to improve the accuracy of estimating the number of prevalences and incidences of disease. Furthermore, applying a method of cross-verification with data sources other than claims data could be helpful in improving the methodology.

Despite these limitations, this study contributes to the understanding of disease burden in Korea by utilizing individual-level empirical data. The methodology employed, such as examining disease burden by region and income level, provides valuable insights into health equity. It is crucial to explore the underlying factors that contribute to health disparities identified in the results. Furthermore, estimating the preventable disease burden by assessing the attributable burden due to health risk factors like smoking, drinking, and lack of physical activity may guide priority setting and goals establishment in health promotion efforts. It is recommended that the burden of disease in the Korean population be regularly measured and the research methodology be continuously improved. The findings from these measurements should be utilized in policymaking to promote health and address health disparities effectively.

Supplementary Table 1

Percentage change in YLDs (per 100,000 population) for the top 20 leading specific causes (levels 3 and 4) of YLDs