EVALUATING THE IMPACT OF ADHERENCE TO DETERMINE THE OPTIMAL START TIME FOR STATINS FOR DIABETES PATIENTS

Purpose: HMG Co-A reductase inhibitors (statins) are an important part of the treatment plan for patients with Type 2 diabetes. However, many patients who are prescribed statins stop taking the drug altogether or take less than the prescribed amount within the first year. This behavior can lessen the drug’s benefit or even cause harm to the patient. We propose a model to optimize the treatment decision for hypercholesterolemia for patients with Type 2 diabetes while considering issues of adherence to medications.

Methodology: Using a longitudinal clinical dataset from the Mayo Clinic electronic medical record we construct a discrete time Markov process defining the progression of patients through health states composed of cardiovascular events, metabolic factors such as total cholesterol and high density lipoproteins (HDL), and adherence levels once statins have been prescribed. The population is defined as patients with Type 2 diabetes, age 40 years and older, with at least 10 years of follow-up after the initial encounter. We further formulate a Markov decision process model and use it to evaluate the optimal start time of statin treatment over the course of a patient’s lifetime for different combinations of patient risk factors and adherence rates drawn from secondary sources.

Results: Our model found that patients at low risk for cardiovascular events should wait to start statins later than patients at high risk. The recommended times for the patients to start statins are sensitive to the likelihood that patients remain adherent. With expected high adherence (60% remaining on statins after three years), patients at low risk should only wait until age 45 to start statins. With expected low adherence (25% remaining on statins after three years), patients at low risk should wait until they are almost 60 years old to start statin treatment. Patients in the higher risk health states generally should start statins at age 40, independent of the expected adherence level.

Conclusions: Adherence levels greatly affect the optimal start time for statins in low risk patients. Assessing a particular patient’s predicted adherence level could help decide when that patient should start statins. Sensitivity to adherence rates indicates that interventions could be valuable for nonadherent patients to help them gain the full benefit of statin medication.