Pattern of Non-Adherence to Statins in Patients of Dominican Descent in an Outpatient Setting

Statins are the standard of care in the management of hypercholesterolemia and there is extensive clinical evidence demonstrating their efficacy in lowering LDL cholesterol and decreasing cardiovascular risk. However, several trials have shown that non-adherence to statin therapy is a relative common issue that may lead to adverse cardiovascular outcomes. Side effects, mostly myalgias, are in general cited as the most common cause of statin discontinuation but other factors may include unfounded fear of side effects, low education and/or low socioeconomic status, patient desire for alternative and/or natural medicines, multiple comorbidities and polypharmacy. Furthermore, age and ethnicity may also play a role in adherence to statins. We performed an observational, cross-sectional study monitoring adherence to statins in 445 patients of Dominican decent in an outpatient setting in a Cardiovascular Clinic and a Lipid Clinic (located in the same medical building).The rate of non-adherence to statins was 24.49% and non-adherence was more common among the patients seen in the Cardiovascular Clinic, as compared to those seen in Lipid Clinic. The most common causes of non-adherence were forgetting to take the medication, fear of side effects, true reported side effects and running out of medication or refills. Other contributing factors are also discussed in detail in our manuscript. These factors need to be considered in devising approaches to enhance adherence to guideline-based therapies.


Introduction
Cardiovascular disease (CVD) is the leading cause of death worldwide, causing 30% of the annual global mortality [1]. In the United States, where the disease is highly prevalent, over one third of the population has CVD Notwithstanding, despite the exorbitant trial evidence that statin therapy is very effective in reducing cardiovascular morbidity and mortality both in primary and secondary prevention, the effectiveness of statins may be significantly compromised by poor adherence [7][8][9]. In the West of Scotland Coronary Prevention Study (WOSCOPS), only 38.7% of the patients in the original statin group were still receiving a statin 5 years after the completion of the trial [8]. In another study with a median follow-up of 4.1 years, the rate of non-adherence to statins was 26%. This led to an 85% increase in all-cause mortality and a 62% increase in cardiovascular mortality [9].
The causes of non-compliance are multifactorial and may include true statin-related side effects, such as myalgias, lack of education and awareness about the long-term benefits of treatment, but also unfounded misconceptions and/or fear about side effects, by both the patients and some physicians, which are not supported by recent large randomized trials [7].
Other reported factors that may potentially lead to non-adherence to statins include younger age, female gender, African American or Hispanic ethnicity, 2 the presence of multiple comorbidities, lower socioeconomic status, cost of the medication and lack of insurance coverage [7,10]. Furthermore, the lack of any apparent immediate benefit, from the patient's perspective, may play an important role in the adherence of the patient to the medication. In one trial, which compared the patient's adherence to statins versus oral antihyperglycemic therapy, the proportion of patients with a 2-year medication possession ratio (MPR)>80% was 52% for statin versus 63% for oral antihyperglycemic therapy (P <0.0001). The median time to discontinuation of statin therapy was also significantly shorter compared with oral antihyperglycemic therapy (284 vs 495 days; P <0.001). There was a 47% greater risk to discontinue statin than oral anti-hyperglycemic therapy [11].
Our small pilot study aims to describe the pattern of compliance to statins in a community of Dominican descent, in an outpatient setting, attempting to identify its prevalence, causes of non-adherence, and the role of the specific setting that a patient is being assessed (Cardiovascular Clinic versus Lipid Clinic).

Patients and Methods
An observational cross-sectional study was performed in an outpatient setting

Results
After compilation and review of the obtained data, analysis of our sample of 445 patients revealed that 109 patients (24.49%) were non-adherent to statins, while the rest 336 patients (75.51%) were adherent ( Table 1).
The rate of non-adherence to statin therapy was greater among the patients assessed in the Cardiovascular Clinic (99 of 387 patients; 25.58%), as compared to the rate of non-adherence of the patients seen in the Lipid Clinic (10 of 58 patients; 17.24%) ( Table 2).
The rate of non-adherence with statin therapy was lower in patients older than 65 years of age (55 of 260 patients; 21.15%), as compared to the rate of non-adherence of patients ≤ 65 years of age (54 of 185 patients; 29.19%) ( Table 3).
The rate of non-adherence to statin therapy was similar amongst men and women (47 of 190 patients; 24.74% versus 62 of 255 patients; 24.31%, respectively) ( Table 4).
In our study, we observed better patient adherence in the group of patients evaluated in the Lipid Clinic rather than in the Cardiovascular Clinic.
Although the results did not quite reach statistical significance, mainly due to the small total number of subjects, this observation clearly suggests that spending more time with a patient to specifically and in detail address the lipid issue (as it occurs in the Lipid Clinic), rather than discussing the lipid problem only as part of multiple other cardiovascular issues (as it occurs in the Cardiovascular Clinic), may significantly improve compliance to lipid-lowering therapy. This observation is also supported by previous comprehensive evidence [16].
Age has been cited as an important factor that may affect the adherence to statins. In a large meta-analysis, age was found to have a U-shaped association with adherence to statins; the oldest (≥70 years) and youngest (<50 years) had lower adherence, as compared to the middle aged (50-69 years) participants [17]. In another large study, however, younger age was associated with lower adherence to statins [10]. In our study, the older patients (>65 years) were more compliant to statins, as compared to younger This has also been reported in previous studies addressing statin nonadherence [7, 18,19]. In our small study in patients of Dominican descent, true reported side effects (mostly myalgias) were responsible for only 13.76% of the cases of non-adherence to statins. This is in contrast to the results of a large survey of statin users, where muscle-related side effects were reported by 60% and 25% of former and current users, respectively, and the primary reason for discontinuation of the statins was side effects of the medication (62% of cases) [20].
In conclusion, consistent with previous studies in diverse patient populations, the rate of non-adherence to statins was quite high in our small study population of Dominican descent, as approximately one quarter of the participants did not comply with their statin therapy. As statin non-adherence has been linked to adverse cardiovascular outcomes, it is imperative that aggressive efforts should be made to improve compliance. Again, the fact that compliance was better in the patients seen in the Lipid Clinic clearly indicates that spending more time with the patients to address their specific lipid-related issues and answer all their relevant questions would be a very promising intervention to improve adherence to statins.
Finally, limitations of our study are the relatively small number of subjects, which did not permit to obtain fully statistically significant results, as well as the fact that the time interval from the initial prescription of the statin to the day of the patient's evaluation in the clinic was not taken into account.
Another limitation of our study is that persistence to statin therapy was not addressed in our study. Nevertheless, our study did reveal significant trends into the pattern of non-adherence to statins in patients of Dominican descent.