Population

The multi-institutional SDR was described in detail previously [11]. Briefly, the SDR was established in 2015, and has been populated with data retrospectively and prospectively to cover the period 2013 to 2019. It is updated annually, with patient data from electronic medical records (EMR) across the primary and hospital-based care continuum within SingHealth. The public healthcare system in Singapore is grouped into three major clusters including Singapore Health Services (abbreviated as SingHealth), National Healthcare Group (NHG), and National University Health System (NUHS). Each cluster provides the full suite of healthcare service from primary care to general hospitals and community hospitals. SingHealth, where SDR is based, is the largest cluster and consists of four acute hospitals, five national specialty centers, three community hospitals and eight primary care clinics (SingHealth Polyclinics) [12], which cumulatively provide health services to approximately 50% of the population of Singapore. Patients with diabetes were identified through diagnosis codes (International Classification of Disease, Nine Revision (ICD 9), ICD10, Systematized Nomenclature of Medicine (SNOMED), and SingHealth Polyclinic Working Diagnosis Code), prescription records for diabetes medications, or laboratory tests (fasting plasma glucose, oral glucose tolerance test, or glycated hemoglobin (HbA1c)). The details of each criterion for identifying diabetes have been published earlier [11]. The SDR includes data on patient demographics, prescribed and dispensed medications, co-morbidities, anthropometrics, laboratory tests, and health services utilization. All-cause mortality and CVD mortality data up till December 2019 were obtained by linking the SDR with the Singapore National Death Registry. ICD 10 codes (codes: I00-I99) were used to identify patients for whom CVD was the primary diagnosis and listed as underlying cause of death. The present study included patients with both type 1 and type 2 diabetes aged ≥ 18 years, enrolled between 2013 and 2019 (n = 209,930). More than 95% had type 2 diabetes. The study was approved by the NUS Institutional Review Board and SingHealth Centralised Institutional Review Board. Informed consent was not sought from patients because the study analyzed anonymised datasets from the SDR in a sandbox environment.