Background: Cardiovascular disease is a leading cause of death in Latin America. Internationally, low medication adherence is associated with 15% to 40% of excess cardiovascular deaths. In Latin America, the magnitude of low medication adherence and the factors associated with it, are not well known, especially among socially vulnerable populations. The aim of this study is to estimate the magnitude and associated factors of low medication adherence in a socially vulnerable population with high cardiovascular risk in Chile. Methods: The study is based on a mixed-methods design. It included a multicenter cross-sectional design of a randomly selected clinical population of 900 participants, and a qualitative design based on the analytical framework model, that included patients and health team members, from three primary care clinics in Chile. Results: Only 24.6% from the 886 (out of 900) patients who completed the study had "high" medication adherence, 24.9% had "regular," and 50.4% had "low" adherence. Depression was the main factor associated with regular and low adherence combined (OR: 2.12; 95%CI:1.55-2.89). Confusion and tiredness were identified as barriers for adherence. Main facilitators reported by patients included better understanding of the medications, and availability of reminders. Clearer information and family support were identified by team members as initiators for improving adherence. Conclusion: Low medication adherence is highly prevalent among patients with high cardiovascular risk in a low-income population in Chile. Quantitatively, depression was a significant risk factor for regular and low adherence; qualitatively, confusion and tiredness were identified as barriers. Clearer information and family support are identified as potential facilitators.

The authors have declared no competing interest.

Cllinicaltrials.gov Prococol Registration NCT05395806

This project is funded by the Chilean National Agency for Research and Development (ANID) (SA20I0001)

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The project was reviewed and approved by the Institutional Review Boards at the Faculty of Medicine Pontificia Universidad Católica de Chile as well as Servicio de Salud Concepción and Servicio de Salud del Maule, Chile (CI200117003).

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes