1. Background

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.

2. Objectives

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.

1. Ethics statement

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

2. Study design

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/.

3. Setting

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.

4. Subjects/data source/measurements

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}.

5. Variables

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

6. Bias

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

7. Study size

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

8. Statistical methods

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

1. Number of deaths and crude death rate

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.

Figure 1.

The annual number of deaths and the crude death rate from 1983 to 2021 in Korea. Illustrated by the author.

2. Life expectancy

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].

3. Deaths according to sex and age

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.

Figure 2.

Trends in sex- and age-specific proportions of deaths, 2011 vs. 2021 in Korea. Illustrated by the author.

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).

Figure 3.

Age-specific mortality rates, 2011–2021 in Korea. Illustrated by the author.

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.

4. Trends in mortality rates by leading causes of death

1) Leading causes of death

The top 10 causes of death, in descending order, were (1) malignant neoplasms (cancer), (2) heart disease, (3) pneumonia, (4) cerebrovascular disease, (5) intentional self-harm (suicide), (6) diabetes mellitus, (7) Alzheimer’s disease, (8) liver disease, (9) sepsis, and (10) hypertensive diseases. Sepsis rose from 10th to ninth place. Together, these 10 causes accounted for 66.0% of all deaths. The top three—cancer, heart disease, and pneumonia—constituted 43.1% of total deaths, reflecting a 1.7 percentage-point decrease from 2020 (Suppl. 4).

Differences in causes of death by sex are presented in Figure 4. For both men and women, cancer remains the leading cause of death, with the male cancer mortality rate 1.6 times higher than that of women. Compared to 2020, the top 10 causes of death for men did not change. Among women, however, coronavirus disease 2019 (COVID-19) appeared in the rankings for the first time, and intentional self-harm rose from 8th to 7th place. By age group, intentional self-harm ranked first among individuals aged 10 to 29, while cancer ranked first for those aged 40 and older. Other notable age-stratified patterns include the following:

Figure 4.

Ten leading causes of death by sex in 2021 in Korea. Illustrated by the author.

Cancer was the leading cause of death among individuals aged 1 to 9 and those 40 years and older. It ranked second among teenagers and those in their 30s, and third among those in their 20s. Heart disease was the second leading cause of death for individuals aged 60 and older and ranked among the top 5 causes for those aged 10 and above. Pneumonia ranked third among individuals aged 80 and older and fourth among those aged 70 and older, indicating a high vulnerability among older adults. Cerebrovascular disease was the third leading cause of death for individuals in their 60s and 70s, fourth among those aged 80 and older, and fifth among teenagers and individuals in their 20s, 40s, and 50s. Intentional self-harm was the leading cause of death for individuals aged 10 to 30, second for those in their 40s and 50s, and fourth for individuals in their 60s. Liver disease ranked third among individuals in their 40s, fourth among those in their 50s, and fifth among those in their 30s and 60s. Transport accidents were the second leading cause of death for individuals in their 20s, third for those aged 1 to 9 and teenagers, and fourth for those in their 30s.

2) Cause-specific mortality rates

In 2021, mortality rates (per 100,000) increased for respiratory tuberculosis (8.3%), Alzheimer’s disease (6.2%), diabetes (6.0%), and sepsis (5.7%) compared to 2020. Conversely, deaths from transport accidents decreased by 8.2%, chronic lower respiratory diseases by 5.5%, and heart disease by 2.4% (Figures 5, 6). Over the past decade, mortality rates have risen significantly for sepsis (242.0%), Alzheimer’s disease (224.2%), pneumonia (158.8%), heart disease (23.5%), and hypertensive diseases (20.6%). In contrast, they have declined for transport accidents (–44.0%), respiratory tuberculosis (–40.4%), chronic lower respiratory diseases (–24.9%), diabetes (–18.8%), and intentional self-harm (–18.1%).

Figure 5.

Mortality rates for major causes of death in Korea. Illustrated by the author.

Figure 6.

Trends in external-cause mortality (e.g., accidents) from 2011 to 2021 in Korea. Illustrated by the author.

3) Mortality from malignant neoplasms (cancer)

The cancer mortality rate was 161.1 per 100,000, representing a 0.6% increase from 2020. The highest mortality rates by organ were observed in the lung (36.8), liver (20.0), colon (17.5), stomach (14.1), and pancreas (13.5) (Figure 7, Suppl. 5). Notable increases from 2020 were recorded for leukemia (11.7%), prostate cancer (7.6%), and uterine cancer (6.3%), while decreases were seen in stomach cancer (–3.4%), liver cancer (–2.9%), and brain cancer (–2.6%). Male cancer mortality (199.0) was 1.6 times higher than that of women (123.4). Among men, the most common cancers were lung (54.5), liver (29.4), and colon (19.6). For women, the leading cancers were lung (19.2), colon (15.4), and pancreatic (12.9). The highest male-to-female mortality ratio was observed for esophageal cancer (8.8:1), followed by lung and liver cancers (2.8:1 each).

Figure 7.

Trends in mortality from malignant neoplasms by organ site from 2011 to 2021 in Korea. Illustrated by the author.

Compared to 2020, mortality rates from all cancers increased by 0.3% in men and 1.2% in women. Over the past decade, deaths from colon, pancreatic, and lung cancers have risen, while those from stomach and liver cancers have declined. By age group, the most common organ-specific cancer mortalities were stomach and breast cancer in individuals in their 30s, liver cancer in those in their 40s and 50s, and lung cancer in those 60 and older (Suppl. 6).

4) Mortality from circulatory system diseases

Overall, mortality due to circulatory system diseases increased by 0.3% from 2020, reaching 121.5 per 100,000 individuals (Figure 8, Suppl. 7). This category encompasses heart disease (61.5), cerebrovascular disease (44.0), and hypertensive diseases (12.1). Compared to 2020, cerebrovascular disease rose by 3.4%, and hypertensive diseases by 2.0%, while heart disease declined by 2.4%. Among heart diseases, ischemic heart disease had the highest mortality rate, at 34.0.

Figure 8.

The mortality rate due to circulatory system diseases by age in 2021 in Korea. Illustrated by the author.

Female mortality rates from circulatory system diseases (126.8) exceeded those of men (116.2) by a factor of 1.1. For hypertensive and cerebrovascular diseases, the rates among women were higher; however, for ischemic heart disease, the rate in men (31.0) surpassed that in women (24.1). Mortality from circulatory system diseases increased sharply from age 70 onward, with heart disease, cerebrovascular disease, and hypertensive disease ranking first, second, and third in all older age groups, respectively. Within the category of heart disease, ischemic heart disease is more prevalent among individuals in their 40s to 60s and remains common among those aged 70 and older (Suppl. 8).

6) Intentional self-harm

The intentional self-harm mortality rate was 26.0 per 100,000, an increase of 0.3 (1.2%) from 2020, resulting in 13,352 intentional self-harm deaths (about 36.6 per day) (Figure 9). Rates rose among individuals in their teens (+10.1%), 20s (+8.5%), and 70s (+7.7%), while they decreased among those in their 60s (–5.7%), 40s (–3.4%), and those aged 80 and older (–2.2%) (Figure 10). The male suicide rate was 35.9, which is 2.2 times higher than the female rate of 16.2. Both rates experienced a slight increase from 2020. The narrowest male-to-female ratio (1.1:1) was observed in the teenage group, while the widest (3.7:1) was found among those aged 80 and older. Intentional self-harm was the leading cause of death for individuals aged 10 to 30 and the second leading cause for those in their 40s and 50s. According to the Organisation for Economic Co-operation and Development (OECD) standard population, Korea’s age-standardized suicide rate was 23.6 per 100,000 in 2021, the highest among OECD countries (OECD average, 11.1) [10–13].

Figure 9.

Number of deaths and mortality rate due to intentional self-harm, 2011–2021 in Korea. Illustrated by the author.

Figure 10.

Age-specific intentional self-harm rates, 2011–2021 in Korea. Illustrated by the author.

7) Alcohol-related deaths

The number of alcohol-related deaths was 4,928, an average of 13.5 per day, which represents a decrease of 227 from 2020 (Figure 11). The mortality rate for alcohol-related causes declined by 4.4%, reaching 9.6. Decreases were observed in nearly all age groups for men (except those in their 20s) and for women (except those in their 70s). The male alcohol-related mortality rate of 16.5 was 6.1 times higher than that of women (2.7). Rates began to rise from the 30s onward, peaking in the 50s and 60s (Suppl. 11).

Figure 11.

Trends in the sex ratio of alcohol-related mortality, 2011–2021 in Korea. Illustrated by the author.

8) Deaths from dementia

Dementia accounted for 10,351 deaths, representing a 2.7% decrease from 2020 (Figure 12). The dementia mortality rate was 20.2 per 100,000, down by 0.6 (2.7%) compared to 2020. Women had a mortality rate of 27.4, which is 2.1 times higher than that of men (12.8). Both sexes experienced a decline from 2020 (Suppl. 12).

Figure 12.

Trends in mortality rates due to dementia by cause, 2011–2021 in Korea. Illustrated by the author.

9) COVID-19-related deaths

There were 5,030 deaths attributed to COVID-19 in 2021, accounting for 1.6% of total deaths. This figure may differ from data reported by the Korea Disease Control and Prevention Agency due to variations in reporting criteria. The COVID-19 mortality rate was 9.8, reflecting a 429.6% increase (up from 7.9) compared to 2020. Mortality rates rose sharply from age 60 onward, reaching 124.0 among those aged 80 and older. Individuals aged 80 and older comprised 49.9% of COVID-19 deaths, and male mortality rates exceeded female rates across all age groups (Figure 13).

Figure 13.

COVID-19-related deaths per 100,000 population by age and sex, 2021 in Korea. Illustrated by the author.

1. Interpretation

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.