Time-to-onset of treatment for hypertension and hyperlipidaemia in South African diabetes mellitus patients: A survival analysis using medicine claims data.

WHAT IS KNOWN AND OBJECTIVE

Hypertension and hyperlipidaemia have high prevalence among diabetics and increase patients' risk of cardiovascular diseases, ultimately affecting prognosis negatively. Medicine claims data have gained prominence in the study of drug-related events and outcomes. There is paucity of publications on the time-to-onset of treatment for these conditions among South African diabetics using secondary data. This study aims to determine the time-to-onset of treatment for hypertension and hyperlipidaemia among diabetics using a South African medicine claims data.

METHODS

Survival analysis was conducted using retrospective data of patients enrolled continuously with a Pharmaceutical Benefit Management (PBM) company in South Africa from 1 January 2008 to 31 December 2016. We identified patients based on International Classification of Diseases, Tenth Revision (ICD-10) diagnoses codes for type 2 diabetes mellitus (E11) who were receiving antidiabetic medication according to the National Pharmaceutical Product Index (NAPPI) codes provided by the Monthly Index of Medical Specialities (MIMS) classification code 19.1 (N = 2996). Among these patients, we then selected those who had ICD-10 codes for hypertension (I10, I11, I12, I13, I15, O10 and O11) who were receiving antihypertensive medications, and those who had hyperlipidaemia (E78.5), who received antihyperlipidaemics during the study period. Data were extracted using SAS system version 9.4 classification codes. The Kaplan-Meier approach, used to compare the survival experience of patients who commenced treatment for hypertension and hyperlipidaemia, was conducted using IBM SPSS version 25. The time to the commencement of treatment of hypertension and hyperlipidaemia among the diabetics were measured in days. With 2008 serving as the index year, we followed up on patients until 31 December 2016.

RESULTS AND DISCUSSION

A total of 494 patients with an average age of 53.5 (SD 11.1) years were included in the study, 34.8% of whom were females. Prevalence of hyperlipidaemia and hypertension among patients were 35.0% and 45.6%, respectively. Average time-to-onset of treatment for hyperlipidaemia was 2684.4 (SD 42.2) days compared to 2434.2 (SD 47.6) days for hypertension. There was no statistically significant difference in age and sex among patients who started treatment for either of these conditions during the study (P = 0.404; Cohen's d = 0.132 for hyperlipidaemia and P = 0.644, Cohen's d = 0.059 for hypertension).

WHAT IS NEW AND CONCLUSION

Within an average of 6 years after an index period of 1 year free of disease, diabetics may commence treatment for hyperlipidaemia, hypertension or both. With all significant data appropriately captured, medicine claims data can be effectively used in survival analysis to determine time-to-onset of treatment for hyperlipidaemia and hypertension among diabetics.