Materials and Methods
The single-payer compulsory National Health Insurance (NHI) program was
initiated in Taiwan in 1995. The program provides universal coverage to
most residents in Taiwan. The NHI Research Database (NHIRD) provided
data about complete outpatient visits, hospital admissions,
prescriptions, catastrophic illness information, and vital status of
99% of Taiwan’s 23 million people. The bureau of the NHI released the
NHIRD for research purposes. In this study, we adopted the data obtained
through the Longitudinal Health
Insurance Database 2005 (LHID 2005) from the NHIRD. This LHID 2005
database included registration and medical claims for 1,000,000 randomly
sampled patients from the total number of NHRI enrollees. The LHID2005
data set allows researchers to follow up on all the medical services
utilized by these 1,000,000 individuals since the initiation of the NHI
in 1995. To protect individual privacy, the original identification
numbers of the beneficiaries’ data were encrypted for privacy.
Encryption procedures were consistent with other datasets and ensured
that all claims data could be linked in order to obtain additional
medically relevant data. All data that could be used to identify
patients or care providers, including the names of medical institutions
and physicians, were encrypted. Our study protocol was approved by the
institute review board of Chang Gung Memorial Hospital, Kaohsiung,
Taiwan without the need of any informed consent.