Depression and antecedent medication adherence in a cohort of new metformin users. Issue 2 (2nd November 2020)

• Record Type: Journal Article
• Authors: Niaz, Diva; Necyk, Candace; Simpson, Scot H.
• Is Part Of: Diabetic medicine. Volume 38:Issue 2(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-02
• Subjects: Depression -- Type 2 Diabetes -- Medication Adherence; Diabetes -- Periodicals; 616.462
• DOI: 10.1111/dme.14426
• Languages: English
• ISSNs: 0742-3071

Abstract

Abstract: Aims: The association between depression and poor medication adherence is based on cross‐sectional studies and cohort studies that measure adherence rates after depression status is determined. However, depressive symptoms occur well before diagnosis. This study examined adherence patterns in the year before a depressive episode. Methods: This retrospective cohort study followed new metformin users identified in Alberta Health's administrative data between 2008 and 2018. Depressive episodes starting ≥1 year after metformin initiation were identified using a validated case definition. Controls were randomly assigned a pseudo depression date. Adherence to oral antihyperglycemic medications was estimated using proportion of days covered (PDC) and group‐based trajectory models to explore the association between depression and poor adherence (PDC<0.8). Results: A depressive episode occurred in 17, 418 (10.6%) of 165, 056 new metformin users. Individuals with depression were more likely to have poor adherence compared to controls (adjusted odds ratio 1.21; 95% CI 1.17, 1.26). Five trajectories were identified: nearly perfect adherence (PDC >0.95 [34.8% of cohort]), discontinued (PDC=0 [18.3% of cohort], poor initial adherence (PDC 0.75) that declined either rapidly (9.2% of cohort) or gradually (30.1% of cohort), and poor initial adherence (PDC 0.26) that increased gradually (7.6% of cohort). Individuals with depression were more likely to be in one of the four trajectories of poor adherence compared to controls (adjusted odds ratio 1.24; 95% CI 1.19‐1.29). Conclusions: Poor medication adherence occurs in the year before a depressive episode; therefore, poor medication use patterns could be used as an early warning sign for depression.