In Korea, cause-of-death statistics are compiled in accordance with the Statistics Act and the Act on the Registration of Family Relations. Death reports, including death certificates, are collected from local administrative offices nationwide. Cause-of-death statistics in the Republic of Korea in 2014 [1], 2016 [2], 2018 [3], 2019 [4], and 2020 [5] have been reported. The present report follows up with data from 2021.

The aim of this study was to examine the causes of death in Korea in 2021. It includes an analysis of the number of deaths, crude death rate (CDR), age-standardized death rate (ASDR), mortality rates by age and sex, and trends in mortality rates by cause of death.

Because this study analyzed publicly available data, neither approval from the institutional review board nor the obtainment of informed consent was required.

This study employed a population-wide, repeated cross-sectional approach utilizing national death certificate data. The research is reported in accordance with the strengthening the reporting of observational studies in epidemiology (STROBE) statement, which can be accessed at https://www.strobe-statement.org/.

This report presents data on causes of death in Korea for the year 2021. We aggregated and analyzed all cases reported over a 16-month period (for example, deaths occurring in 2022 were reported from January 2022 to April 2023). To ensure the completeness of the reporting period and the timeliness of statistical data, a 16-month aggregation method for death reporting was chosen. Although the legal deadline for death registration is within one month, requiring at least 13 months of data collection, reports beyond 17 months are minimal. For 2021, death registrations after 16 months accounted for only 0.15% of the total deceased population. According to the World Health Organization's guidelines, each death is classified based on the underlying cause of death.

The data collection and analysis methods were consistent with those used in the previous study on cause-of-death statistics, spanning from the 2016 study [2] to the 2018–2020 studies [3–5]. Data were obtained from death certificates issued in 2021 for individuals of Korean descent who resided in the Republic of Korea [6].

Two supplementary procedures were employed to improve data quality. First, an infant mortality survey is conducted because infant deaths are often underreported. It involves independent surveys of medical institutions and the collection of cremation data from all crematoria nationwide. Second, administrative record linkage is used to verify the accuracy of reported causes of death. This process involves individually cross-referencing 22 sets of administrative data, including national health insurance claims, cancer registry data, police investigation records, autopsy reports, and more.

The analysis and classification were conducted using mid-year population figures, employing the disease classification recommended by the World Health Organization [7] and the Korean Standard Classification of Diseases and Causes of Death (KCD-7) [8]. The data were then analyzed to calculate the CDR, ASDR, and cause-specific mortality rates. The data obtained from Statistics Korea are available in Data Set 1.

All causes of death were considered as variables in the data analysis.

To address residual misclassification and underreporting related to infant mortality, we cross-referenced our findings with other data sources.

The entire population of the Republic of Korea was included in the study, and no sample size estimation was necessary.

Descriptive statistics were utilized to present the results of the data analysis.

In 2021, there were a total of 317,680 deaths, representing an increase of 12,732 (4.2%) from 2020. The number of male deaths was 171,967, reflecting an increase of 4.1% from 2020 (Figure 1, Suppl. 1). The number of female deaths was 145,713, also showing a 4.2% increase from 2020. The average daily number of deaths was 870, which is 37 more than in 2020. The CDR (the number of deaths per 100,000 population) was 618.9, indicating an increase of 25.0 persons (4.2%) from 2020. The CDR for men was 672.0, an increase of 27.0 (4.2%), while the rate for women was 566.0, reflecting an increase of 23.0 (4.2%) from 2020. The ASDR, which accounts for differences in age distribution, was 317.7, representing a 12.8 increase from 2020.

Life expectancy at birth in 2021 was 83.6 years, reflecting an increase of 0.1 years from 2020, when it was 83.5 years. In 2021, life expectancy at birth for men was 80.6 years, while for women it was 86.6 years [9].

Individuals aged 80 or older accounted for 50.0% of total deaths, representing a 1.3 percentage-point increase from 2020. Compared to a decade ago, this proportion has risen by 15.2 percentage points (Figure 2, Suppl. 2). Among men, 37.4% of deaths occurred in individuals aged 80 and above, reflecting a 14.8 percentage-point increase over the past 10 years. Among women, 64.8% of deaths were in those aged 80 and older, marking a 14.7 percentage-point increase over the same period. By age group, the most significant increases in deaths were observed among individuals in their 60s (8.2%), those aged 80 and older (7.0%), and those in their 20s (2.7%) compared to 2020. The sex ratio (male deaths to female deaths) was highest in the 60s age group, at 2.7 to 1.

In terms of age-specific mortality rates (Figure 3, Suppl. 3), rates increased among teenagers (3.5%), individuals in their 20s (3.8%), those in their 60s (1.3%), and individuals aged 80 and older (0.3%). By age group, the lowest mortality rate was observed in those aged 1 to 9 (8.0 per 100,000), while the highest was found in individuals aged 80 and older (7,847.3 per 100,000).

Male mortality increased by 4.2% to 672.0 per 100,000, while female mortality also rose by 4.2% to 566.0 per 100,000, both in comparison to 2020. Males experienced heightened age-specific mortality rates in their teenage years, 20s, 60s, and among those aged 80 and older, whereas women primarily saw increases among teenagers and those in their 60s. Mortality rates for men surpassed those for women across all age groups, with the largest ratio (2.8:1) observed in the 60s.

The total number of deaths in 2021 reached the highest level since the inception of cause-of-death statistics in 1983. The CDR of 618.9 is also the highest recorded since 1984, when it was 585.2. Korea’s aging population continues to drive increases in both total deaths and the CDR. In 2021, the population aged 65 and older grew by 5.4%, while deaths in this demographic rose by 5.6%. Of the 12,732 additional deaths compared to 2020, 13,224 occurred in the 65-and-older group, whereas deaths under age 65 actually decreased by 490.

In 2021, Korea experienced a net population reduction. The country recorded 260,600 live births, reflecting a decline of 11,800 (4.3%) compared to 2020 [6]. The total fertility rate for 2021 was 0.81 children per woman, continuing the trend of ultra-low birth rates. With total deaths reaching 317,680, there was a net population decrease of 57,080, excluding the effects of immigration and emigration. This trend is likely to persist unless the total fertility rate is restored.

Sepsis entered the top 10 causes of death in 2020 and rose to ninth place in 2021, overtaking hypertensive diseases. It involves a systemic inflammatory response (e.g., fever, tachypnea) triggered by microbial infection, posing significant risks for older adults and those with chronic conditions. Because early symptoms can be subtle, sepsis can progress rapidly, underscoring the need for comprehensive management alongside other age-related conditions such as Alzheimer’s disease and pneumonia.

Among women, hypertensive diseases moved up to seventh place, replacing intentional self-harm, and COVID-19 emerged as the 10th leading cause of death, replacing chronic lower respiratory diseases (Figure 4). There was no change in the top 10 causes of death for men.

Deaths from transport accidents have steadily declined, likely due to the establishment of school zones for children in 1995, the 2020 implementation of a road safety law aimed at protecting children in school zones [10], stricter penalties for driving under the influence, and increased societal emphasis on safe driving practices.

Intentional self-harm deaths increased in 2021, with reported rises in methods such as medication overdose and jumping. The COVID-19 pandemic has significantly exacerbated depression, unemployment, and financial stress for many in Korea. Studies indicate that pandemic-related job loss heightened the risk of depression and suicidal ideation, especially among adults with lower income and education levels [11]. Research on the first 10 months of COVID-19 in Korea found that approximately 1.1 million jobs were lost—4.2% of non-farm employment as of April 2020—and these losses continued through December 2020 [12]. Korea’s intentional self-harm mortality rate of 26.0 per 100,000 is the highest among 38 OECD countries (OECD average, 11.1) [13]. In response, the Ministry of Health and Welfare has established the “National Suicide Prevention Action Plan,” seeking to reduce the suicide death rate to below 20 per 100,000 and total suicides to fewer than 10,000 per year [14]. More proactive policies are required, including restricting access to lethal means, implementing school-based awareness programs, offering pharmacological and psychological treatments for depression, providing gatekeeper training programs, educating physicians, and expanding Internet and helpline support [15]. Among gatekeeper training programs, “Suicide CARE” is widely used in Korea for the early detection of suicidal risk. The program consists of 3 parts: “Careful observation” (detecting verbal and non-verbal signals for self-harm), “Active listening” (hearing the reasons for suicidal intent), and “Risk evaluation and Expert referral” (connecting at-risk individuals to psychiatric professionals) [16]. Physician participation in such programs is crucial to reducing intentional self-harm.

Older patients in long-term care hospitals face significantly higher odds of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (odds ratio [OR], 2.91; 95% confidence interval [CI], 2.33–3.64) and COVID-19 mortality (OR, 3.58; 95% CI, 2.13–6.02) [17]. From January 2020 to August 2023, 35,605 COVID-19-related deaths were recorded in Korea, with over 90.0% of these occurring in older adults or those with underlying health conditions. The case fatality rate was 0.10%, and the mortality rate was 69 per 100,000 people. Among all age groups, the highest case fatality rate (1.75%) was observed among individuals aged 80 and older. Korea’s COVID-19 case fatality rate remains among the lowest in the world [18]. The 5,030 COVID-19 deaths in 2021 were also among the lowest totals globally, attributable to stringent quarantine measures and high-quality medical care.