Adherence to statin therapy poor in both primary- and secondary-prevention patients

June 08, 2004

Cleveland, OH - Statin adherence among patients treated for primary and secondary prevention of CHD was equally poor, according to the results of a new study[1]. Regarding the suboptimal adherence and increased rates of discontinuation, investigators found that copayment coststhe monthly out-of-pocket expensesare a major factor in patients not sticking to their medication.

"There are not a lot of real-world data out there looking at adherence and discontinuation of statin therapy, especially in the context of patients with more severe cardiac disease," lead author Dr Jeffrey Ellis (Cleveland Clinic, OH) told heartwire . "Looking at just nonadherence, we found that the primary and secondary groups were practically equal in terms of taking their medications, which is really quite surprising, because we thought the sicker patients, those who had had an MI or underwent surgery, would realize the importance of sticking with their medications."

The results of the study are published in the June 2004 issue of the Journal of General Internal Medicine.

Adherence and discontinuation

To compare adherence and discontinuation rates in primary- and secondary-prevention populations and to identify modifiable factors that may affect these behaviors, investigators retrospectively reviewed medical and claims data from a managed-care organization in the US. In total, 2544 primary- and 2258 secondary-prevention patients were identified. All patients were 18 years of age and older and filled at least two statin prescriptions between 1998 and 2001.

Adherence was measured by the patient's cumulative multiple-refill-interval gap (CMG). CMG is defined as the number of days without medicationthe gapdivided by days of active statin use. A CMG may range from 0%, indicating total adherence, or no gap days, to 100%, complete nonadherence. In this study, patients were considered nonadherent if the CMG was greater than 10%, indicating missed medication more than one day out of every 10. For rates of discontinuation, any patient who began statin therapy was assumed to require treatment for life, regardless of CHD risk level.

On average, adherence was poor in both the primary- and secondary-prevention groups, with the primary and secondary cohorts going without medication 20.4% and 21.5% of the time, respectively (p=0.149). Primary-prevention patients, however, were more likely to discontinue statin therapy.

"We found that day-to-day adherence was equal between the groups, but in terms of outright discontinuation, there were some greater levels of retention in the sicker population, the secondary-prevention patients," said Ellis. "They were staying on their medication longer than their primary-prevention counterparts, even though they might have been missing the same amount of medication over the course of a month."

Nonadherence in primary and secondary prevention, as well by as copayment

Prevention category CMG >10% CMG >20% CMG >30%
Overall (%) 56.2 38.3 27.3
Secondary (%) 56.0 38.8 26.7
Primary (%) 56.4 37.8 28.0
Range of mean prescription copayment (%)      
 <$10 49.3 28.6 22.2
 $10 to <$20 60.0 39.7 28.4
>$20 76.2 59.4 45.1

Ellis and colleagues report that the increasing magnitude of patient cost sharing had a large, negative effect on adherent behavior. More than 75% of patients with monthly copayments of $20 or more did not adhere to statin therapy, whereas only half of those who paid less than $10 were nonadherent. Even under liberal definitions of nonadherenceas defined by different CMG intervalsthe copayment effect was still significant.

"It wasn't that we weren't expecting the effect of copayments on adherence, but it was the drastic effect that surprised us," said Ellis. "When we divided up our patients into those who were paying less than $10 vs those who were paying more than $20 for their statin, the discontinuation rates were more than four times greater."

Adjusted odds ratio for nonadherence to statin therapy

Variable CMG >10% odds ratio (95% CI) CMG >20% odds ratio (95% CI) CMG >30% odds ratio (95% CI)
Age <65 years 1.25 (1.08-1.45) 1.31 (1.13-1.52) 1.26 (1.07-1.49)
Female gender 1.24 (1.10-1.40) 1.13 (1.01-1.29) -
Copayment $10 to <$20 1.45 (1.25-1.69) 1.30 (1.11-1.51) 1.25 (1.06-1.48)
Copayment >$20 3.23 (2.55-4.10) 3.11 (2.48-3.89) 2.73 (2.16-3.45)
Multiple doses per day 1.88 (1.55-2.27) 1.71 (1.43-2.05) 1.61 (1.33-1.94)
Average days of supply, 0 to <35 2.17 (1.77-2.65) 2.43 (1.93-3.06) 3.58 (2.66-4.82)
Average days of supply, 35 to <65 1.74 (1.43-2.12) 1.91 (1.51-2.40) 2.59 (1.92-3.49)

In the discussion section of their paper, Ellis and colleagues report that the results would support the argument that modern cost-containment strategies are failing to constrain drug cost growth while also failing to optimize essential drug utilization. They suggest that a copayment structure based on potential clinical benefit rather than drug acquisition cost would alleviate some of the financial burden and allow patients to prioritize their out-of-pocket expenditures.

"For patients who are at greater risk for coronary heart disease, those individuals should have lower copays for their medications," said Ellis. "It is more important, in the grand scheme of healthcare dollars, for these folks to be on statin therapy. In the long run, you're going to save the healthcare system from future costs by giving them lower copays now for their statin."


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