Abstract 1349: The Economic Consequences of Non-Adherence to Lipid-Lowering Therapy: Results From the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT)
Background: In the lipid-lowering arm of ASCOT, hypertensive patients at high risk randomized to 10 mg atorvastatin had a 36% reduced risk of non-fatal MI or fatal CHD, and a 21% reduction of any cardiovascular event, compared to placebo. The lipid-lowering arm was discontinued early, due to the beneficial effects, and patients were allowed to stay on lipid-lowering therapy until the completion of the blood-pressure lowering arm (an additional 2.2 years of follow-up). The objective of the present analysis was to assess the impact of low adherence to drug (defined as <50% of days covered), compared to high adherence to drug (>80% of days covered) in terms of risk of events and long-term economic consequences.
Methods: Cox-proportional hazards and Poisson regression models were used to assess the risk of events (defined as any cardiovascular event or procedure) associated with low adherence adjusting for age and baseline cardiovascular risk in patients who did not suffer an event during the randomized part of the trial (n=4671). To assess the long term economic implications of low adherence, the predicted risk adjustments were incorporated into a Markov model. The model predicts the long-term costs, quality of life, and survival implications and utility decrements caused by MI, stroke and revascularization, based on the ASCOT trial data. All analyses were conducted from the perspective of the UK payer, expressed in $ using an exchange rate of £1=$0.61.
Results: The risk of events were lower in patients with high adherence (Cox model: 0.75; 95% CI: 0.56–0.98, Poisson model hazard ratio: 0.73, 95% CI 0.58–0.98). Discounted at 3.5% per year, the Markov model predicts that as a consequence of higher adherence during the follow-up period, costs would be higher ($4,936 per patient compared to $4,388 per patient) due to higher drug costs, but the projected survival and quality-adjusted survival (QALY) would also be longer (10.83 compared to 10.81 life years and 8.13 compared to 8.11 QALYs).
Conclusion: Given the higher risk of cardiovascular events associated with low adherence shown here, measures to improve adherence are an important part of the prevention of cardiovascular disease.