Depressive symptom dimensions and medication non-adherence in suboptimally controlled type 2 diabetes

Aims: Research suggests differential effects for somatic and cognitive-affective depressive symptoms in predicting health outcomes. This study evaluated differential relations with medication non-adherence among disadvantaged, and predominantly immigrant adults with sub-optimally controlled type 2 diabetes (T2D).

Methods: Health plan members taking oral diabetes medication and who had A1c ≥ 7.5% were recruited for a trial of telephonic self-management support. A subset (n = 376; age, M = 55.6 ± 7.2 years; A1c M = 9.1% ± 1.6) completed the Patient Health Questionnaire-8 (PHQ-8). Diabetes medication adherence was measured by self-report and claims-based records. Multivariable logistic regression modeled depressive symptoms and odds of non-adherence using pre-intervention data.

Results: A positive PHQ-8 screen (OR = 2.72 [95%CI: 1.56-4.73]) and each standard deviation increase in PHQ-8 score (OR = 1.40 [95%CI: 1.11-1.75]) were associated with non-adherence, with no independent effects for somatic versus cognitive-affective symptoms. Exploration of individual symptoms identified three significantly associated with non-adherence in covariate-adjusted models; after adjustment for likely presence of clinical depression, only fatigue was independently associated with non-adherence (OR = 1.71 [95%CI: 1.06-2.77]).

Conclusions: Findings support depression symptom severity as a significant correlate of medication non-adherence among disadvantaged adults with T2D. Support was limited for differential associations for symptom dimensions, but findings suggest that fatigue may be associated with non-adherence independent of the likely presence of depression.