*2.1. Data Source*

We used the National Health Insurance Research Database (NHIRD) of Taiwan from 1 January 2009 to 31 December 2013. The NHIRD contains all medical data, including information on disease diagnosis, drug prescriptions, medical operations, and medical expenses of insurance claims data. The National Health Insurance covered more than 99% of Taiwan's population by 2010. The Longitudinal Health Insurance Database 2010 included data from 1 million people randomly sampled from the NHIRD and who were registered by the end of 2010. Diagnostic codes were recorded according to the International Classification of Diseases, Ninth Edition, Clinical Modification (ICD-9-CM). This study was approved by the ethical review board of Chung Shan Medical University Hospital (CSMU No. CS 18096).
