Previous work has established that the chronically ill are sensitive to the cost of prescription drugs. Our study looked at one component of utilization: the initiation of drug therapy after diagnosis. We found that increased cost-sharing delays the initiation of medications to treat newly diagnosed chronic disease, suggesting that out-of-pocket costs may prevent patients from initiating medically necessary care.
In addition, we found that the initiation of drug therapy and sensitivity to prices depends on a patient's "experience" with prescription drug use. Relative to those without experience, patients with experience using prescription drugs were less price-sensitive and adopted therapy earlier, suggesting that patients differ in their willingness to initiate prescription drug therapy. In some patients, an initial resistance against treatment may be reduced once experience using prescription drugs is established. We found no threshold effect for the number of prior or concurrent medications at which the results of our models changed. Thus, our data suggest that out-of-pocket costs may prevent patients from initiating treatment – which could negatively impact health outcomes – but the magnitude of this effect strongly depends whether patients have experience used drugs in the past.
Our survival estimates were consistent with epidemiological studies from NHANES and other sources that estimate the proportion of patients who are aware they have a medical condition but remain untreated.32–54
In our study, the proportion of newly diagnosed patients who had not initiated anti-hypertensive, anti-cholesterol, or anti-diabetes drug therapy by five years was 21.4%, 36.0%, and 32.5%, respectively. Consistent with our data, a variety of studies indicate that the proportion of patients aware of their hypertension but without drug treatment ranges from 8% – 68%.32–39,53
In the Framingham Heart Study, 68.3% of patients with newly diagnosed hypertension had not initiated antihypertensive therapy by four years, including 53.9% of those with Stage II hypertension at baseline,53
and recent estimates range from 8% in a VA population34
to 38–55% in a community population.35
Untreated hypercholesterolemia among those aware of their condition is a well documented and chronic problem. Our estimate of the proportion diagnosed but untreated by five years is at the lower end of most population-based estimates, which range from 25% to 66%.32,36,41,42,46,51
Among diagnosed diabetics, estimates of the proportion without drug treatment range from 8% to 47%.45,50,56
Recent analyses of NHANES yield estimates ranging from 19%–28.6%,32,36,47–49
and even 23.2% of diabetics who survived a myocardial infraction or stroke, a group likely to be hyper-vigilant about controlling cardiovascular risk factors, did not use antidiabetic medications.47
Although our estimate of the proportion of new diabetics who remained untreated after five years was slightly higher than NHANES estimates, NHANES subjects carried their diagnosis for two to three times longer than our five-year follow up period,32,57
and the proportion of untreated diabetics increases with age.45,55
There are several limitations to our study. First, our sample may not be generalizable to a younger population. However, Medicare Part D has increased the proportion of elderly retirees who have prescription drug insurance, and CMS has control over the basics of benefits design. Thus, our results may be particularly relevant for federal policy-makers setting standards for Medicare Part D insurance packages. Second, we could not completely control for selection of drug benefits. However, in all but two employers in the sample, employees had no choice of drug benefits, minimizing the possibility that employees selected plans suited to their anticipated needs, and patients in these two employers accounted for less than 2.5% of the sample. Excluding these patients did not change our results. Third, despite controls for comorbidities, disease severity may differ between patients with and without prior drug experience. Although administrative data do contain detailed clinical information contained in medical charts, our sensitivity analyses examining inclusion criteria designed to produce samples with more homogenous and severe disease did not change our findings. One initial treatment option for patients newly diagnosed with less severe disease is to initiate non-pharmaceutical therapy, such as diet modification and exercise. However, there was no a priori reason that disease severity was correlated with benefits generosity, since almost no patients in our study had a choice of drug benefits plans. Further, analysis of the NHANES has shown that patients diagnosed with hypertension without pharmacologic treatment have, for example, disease severe enough to warrant treatment (SBP>140).52
Despite these limitations, our results suggest a novel distinction between groups of patients, some of whom are price-sensitive to prescription drugs and others who are not. Although the majority of patients in our sample did have experience using prescription drugs, the large impact of cost-sharing on those without experience make this population a prime target for interventions to encourage appropriate treatment of chronic disease, particularly diseases that contribute to cardiovascular risk, such as those included in our study. Future research should explore the mechanisms underlying our results, such as the factors that may influence the effect of cost-sharing within specific patient populations, and should examine the health outcomes of varying times to initiation of drug therapy for chronic disease.
Our findings have implications for policy makers designing insurance benefits and for physicians treating patients with chronic disease. First, these results raise concerns about high cost-sharing levels for elderly, insured patients without experience using prescription drugs. Based on our findings, high cost-sharing levels could be a barrier to treatment for this population, and possibly result in poor health outcomes. Physicians should also heed these findings when treating patients with a new diagnosis of hypertension, hypercholesterolemia, or diabetes; those who do have experience with pharmacologic therapy may be much less likely to initiate prescribed treatments and may be very sensitive to cost-sharing levels.
More broadly, these results add to the growing chorus that our reliance on blunt instruments to influence prescription drug utilization, such as formularies and tiered copayments, which are primarily used to manage cost, need to be updated by more sophisticated tools that take into account therapeutic need as well as patients' complex response to insurance benefits.58,59
For example, recent evidence indicates that among people who have initiated medications for chronic disease, patients are less likely to adhere to their regimen if they begin with high copayments when compared to patients that begin with lower copayments that gradually increase.60
This suggests that new users are likely to be more price sensitive than continuing users, and is congruent with our finding that patients with prescription drug experience are less price-sensitive. Lessons such as these need to be incorporated into benefits design to ensure that patients who require medical therapy are not discouraged from initiating treatment.