2.1 Study design
We conducted a population-based nested case-control study using the
claims data of the Taiwan National Health Insurance program. Taiwan has
implemented a mandatory health insurance program providing comprehensive
medical care coverage to more than 99.9% of the 23 million
residents[21].
We used the longitudinal dataset containing claims data for 1 million
individuals randomly selected from people insured by the National Health
Insurance program in 1996–2000. For each individual in the dataset,
longitudinal medical records from 1996 to 2013 can be obtained by data
linkage between inpatient files, outpatient files, prescription drugs,
and registry for beneficiaries using an encrypted, unique personal
identification number. This study was approved by the Institutional
Review Board at the China Medical University Hospital.