Data acquisition

The data set was provided by the Korean National Health Insurance Service (NHIS), which was founded in 2000 as a single-insurer system. The NHIS has integrated more than 366 of the medical insurance organizations in the Republic of Korea, and stored and converted medical records of individuals into a national database called the National Health Information Database. That database contains personal information, demographics, and medical treatment data for Korean citizens who were categorized as insured employees, insured self-employed individuals, or medical aid beneficiaries.

The NHIS-Senior Cohort (NHIS-SC) is a research database for the elderly constructed in a cohort format for use when investigating the risk factors and prognoses of geriatric diseases. The NHIS-SC was constructed using a simple randomization method to extract data on 557,195 persons, representing 10% of the 5.5 million population aged 60 years or older, who had maintained their health-insurance and medical-care statuses at the end of December 2002.

The members of the NHIS-SC comprise a 14-year cohort (2002–2015) and are tracked in terms of socioeconomic variables (residence area, year and month of death, cause of death, and income level) and medical treatments (health examinations, medical-care history, and medical-care institutions). These data enable long-term observations and can be used to investigate causal relationships.

Diseases are registered in the NHIS-SC using the Korean Classification of Disease, sixth edition, which is modified from the International Classification of Disease, 10th revision (ICD-10) for use by the NHIS and medical-care institutions in South Korea.

This study was approved by the Institutional Review Board of Kangwon National University Hospital (approval no. KNUH-2018-05-004-001).