Patterns of metformin use and glycated haemoglobin trends among patients with newly diagnosed type 2 diabetes in Alberta, Canada

Abstract

Aim: Canadian guidelines recommend metformin as first-line therapy for incident uncomplicated type 2 diabetes and the vast majority of patients are treated accordingly. However, only 54% 65% remain on treatment after 1 year, with the highest discontinuation rates within the first 3 months. The purpose of this study was: (a) to identify individual and clinical factors associated with metformin discontinuation among patients with newly diagnosed uncomplicated type 2 diabetes in Alberta, Canada, and (b) describe glycated haemoglobin (HbA1c) trajectories in the first 12 months after initiation of pharmacotherapy, stratified by metformin usage pattern.

Materials and methods: We conducted a retrospective cohort study using linked administrative datasets from 2012 to 2017 to define a cohort of individuals with uncomplicated incident type 2 diabetes. Using logistic regression, we determined individual and clinical characteristics associated with metformin discontinuation. We categorized individuals based on patterns of metformin use and then used mean HbA1c measurements over a 12-month follow-up period to determine glycaemic trajectories for each pattern.

Results: Characteristics associated with metformin discontinuation were younger age, lower baseline HbA1c and having fewer comorbidities. Sex, income and location (urban/rural) were not significantly associated with metformin discontinuation. Individuals who continued metformin with higher adherence and individuals who discontinued metformin entirely had lowest HbA1c values at 12 months from treatment initiation. Those who changed therapy or had additional therapies added had higher HbA1c values at 12 months.

Conclusion: Identifying characteristics associated with discontinuation of metformin and individuals' medication usage patterns provide an opportunity for targeted interventions to support patients' glycaemic management.

Keywords: antidiabetic drug; cohort study; glycaemic control; metformin; type 2 diabetes.