JMIR Publications

ABSTRACT

Background:

Cardiovascular disease (CVD) is the leading cause of death globally and in Canada. Diabetes and hypertension are major risk factors for CVD events. Despite the increasing availability of effective treatments, majority of diabetic and hypertensive patients do not have adequate blood pressure and glycemic control. One of the major contributors is poor treatment adherence.

Objective:

This study aims to evaluate the impact of treatment adherence for patients with both diabetes and hypertension on acute severe CVD events, and intermediate clinical outcomes in Canadian primary care settings.

Methods:

We will conduct a population-based retrospective cohort study of patients living with both diabetes and hypertension in Ontario, Canada between January 1 2008 and March 31 2018. The Social Cognitive Theory will be used to explain the reciprocal relationship between treatment adherence, personal factors and environmental determinants, and how this interplay impacts CVD events and clinical outcomes. Data will be derived from the Diabetes Action Canada National Data Repository. Linking this cohort to the administrative databases, we will identify the cause of death for patients who died during the follow-up period to define CVD mortality. A time-varying Cox proportional hazards model will be used to estimate the impacts of treatment adherence on CVD morbidity and mortality. Multivariable Poisson regression model and hierarchical regression model will be used to estimate the associations between treatment adherence of different medication categories and intermediate clinical outcomes. Our primary outcome is the association between treatment adherence and the risk of acute severe CVD events, including CVD mortality. The secondary outcome is the association between treatment adherence and intermediate clinical outcomes including diastolic and systolic blood pressures, glycated hemoglobin, low-density lipoprotein cholesterol, and total cholesterol. Due to data limitation, we use medication prescriptions as a proxy to estimate treatment adherence. We assume that patient adhered to medications if s/he had any prescription record in the four preceding quarters and one quarter after each quarter of interest. Acute severe CVD events are defined based on the World Health Organization MONICA Project (monitoring trends and determinants in cardiovascular disease), including acute coronary heart disease, stroke, and heart failure.

Results:

The project was funded in July 2017 by Diabetes Action Canada (503854). The results are expected to be finished by September 2019.

Conclusions:

The findings will be helpful to identify the challenges of treatment adherence for diabetic and hypertensive patients in primary care settings. This will also help to develop intervention strategies to promote treatment adherence for patients with multi-morbidities.