Patient adherence, a key factor should be considered in statin-related observational studies
Ramos and his colleagues (1) conducted a retrospective cohort study to assess the association of statins with a reduction in cardiovascular disease (CVD) and mortality in older adults aged 75 years or older in primary prevention. I applaud that the authors have done a very meticulous work on both data analysis and interpretation.
However, I noticed that patient adherence to statin therapy was not considered in their study, which is a key determinant in ensuring optimal benefits of statin treatment. In Ramo et al (1) study, patients with at least two invoices for statins were categorised as statin-users and further involved in a series of analyses, without taking patient adherence into account. A previous systematic review by Ofori-Asenso et al. (2) reported that the adherence of statin therapy in older adults aged 75 years or older in primary prevention was only 37.7%. Obviously, such low adherence would largely compromise and even deprive the protective effect of statins against CVD and mortality. Of note, given only "new statin users" were included in Ramo et al's study, the adherence rate of statins might be even lower than the general older statin-users in the real-life situation. In this scenario, I am afraid the results of this study may be invalid and would possibly mislead clinicians and patients.
Given no significant association was detected between statins and a reduction in CVD and mortality in healthy adults aged ≥ 75 years without diabetes and adults aged ≥ 85 years with diabetes in Ramo et al. study, we wonder if Ramo and his colleagues can roughly calculate patients' adherence of statins based on their medical record of medication prescription and only enroll patients with good adherence in their analysis.
1. Ramos R, Comas-Cufí M, Martí-Lluch R, et al. Statins for primary prevention of cardiovascular events and mortality in old and very old adults with and without type 2 diabetes: retrospective cohort study. BMJ. 2018 Sep 5;362:k3359. doi: 10.1136/bmj.k3359
2. Ofori-Asenso R, Jakhu A, Ella Zomer, et al. Adherence and Persistence Among Statin Users Aged 65 Years and Over: A Systematic Review and Meta-analysis, The Journals of Gerontology 2018;73(6): 813–9, doi: 10.1093/gerona/glx169
Competing interests: No competing interests