ELICITING LIPID MANAGEMENT GUIDELINES' VALUATION OF FUTURE LIFE
Purpose: Discount factors are critical in assessing the cost effectiveness of treatments as they reflect the time value of costs and benefits. We considered the trade-off between the benefits and side effects of statins to elicit the discounted present value of each future life year for current lipid management guidelines.
Method: We formulated the statin initiation problem for Type 2 diabetes patients as a Markov decision process where the state of the process is defined as the patient's total cholesterol and high density lipoprotein (HDL) levels, and the statin initiation decision is revisited annually. We considered six guidelines: Adult Treatment Panel (ATP) III, Canadian, British, European Union, Australian and New Zealand. For each guideline, we used inverse optimization to find the discounted present value of each future life year that makes the guideline non-dominated with respect to total expected QALYs prior to a first major cardiovascular event and the risk of a first major cardiovascular event. For patients diagnosed with Type 2 diabetes at age 40, we used Mayo Clinic electronic medical records to model the progression of their total cholesterol, HDL, triglycerides, systolic blood pressure, and HbA1c. We incorporated the adverse effects of statins into the model using a constant disutility factor.
Result: Among all guidelines we considered, the underlying present values of future life years for males were never more than those of females. The present value of a life year for males varied from 20% to 70% of that for females between ages 45 and 65. All guidelines were consistent in discounting future with time-varying annual discount factors. Guidelines which initiate statins at earlier ages, such as ATP III, valued the far future more than those which initiate statins relatively later. For males, all guidelines exhibited a sharp decrease in discounting life years after age 45; for females this threshold was at age 55. While no guideline discounted the value of a life year immediately following the diagnosis of Type 2 diabetes, all guidelines were consistent with a present value of <0.001 years beyond age 80.
Conclusion: Our analyses show that guidelines discount future life years with time-variant annual discount factors and show a substantial difference between the implied present value of life years for males and females.