Abstract
Background and Rationale: Type 2 diabetes mellitus (T2DM) is associated with an increased risk
of cardiovascular diseases (CVD) due to abnormalities in lipid metabolism. Patients with T2DM commonly
have elevated levels of triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C), contributing to
the development of atherosclerosis and subsequent cardiovascular occlusion. Primary prevention using
statins therapy is therefore recommended to reduce the risk of CVD in this population. This study aimed
to examine trends in first-time prescriptions of atorvastatin and simvastatin for primary prevention of
CVD among patients with T2DM, and to evaluate the impact of reclassifying atorvastatin from the special-access drug list (List E) to the essential drug list (List B) on statin prescription rates, CVD incidence,
and statin-associated adverse drug reactions (ADRs).
Methods: The study included T2DM patients receiving care at community hospitals in Lampang
province between fiscal years 2018 and 2022, using data from the Ministry of Public Health’s Health Data
Center (HDC). The study was divided into two parts. Part 1 analyzed prescribing shifts using an interrupted
time series (ITS) analysis. Part 2 assessed one-year incidence rates of CVD and ADRs in T2DM patients on
atorvastatin and simvastatin for CVD primary prevention using a retrospective cohort study design. The
CVD incidence was calculated as cases per 1,000 person-days and adverse drug reactions were reported
as percentages.
Results: A total of 5,200 T2DM patients were identified between fiscal years 2018 and 2022. Initial
statins prescriptions for CVD primary prevention were given to 662 patients, representing a prevalence
of 12.8%. The most commonly prescribed statins were simvastatin 20 mg, followed by simvastatin 10
mg and atorvastatin 40 mg. Following the drug list reclassification of atorvastatin, increased trends of
simvastatin 10 mg and atorvastatin 40 mg were observed (19.2% and 10.5% respectively). Conversely,
simvastatin 20 mg prescribing decreased by 4.3% (p-value > 0.05). A 1-year incidence rate of ischemic
heart disease was 0.00671 per 1,000 person-days for patients receiving atorvastatin 40 mg, and 0.00896
per 1,000 person-days for simvastatin 10 or 20 mg. The incidence rate ratio was 0.75 (95% CI: 0.02–4.68).
Conclusion: This study revealed a relatively low rate of statins prescriptions for CVD primary prevention among T2DM patients. This study did not find the effect of prescribing shift or changes in CVD
primary prevention in T2DM patients. Overall, the incidence of ischemic heart disease among statin-treated
patients was low.
