Identifying depressive symptoms in patients with type 2 diabetes mellitus: the role of glucose variability and concomitant hypothyroidism

PurposeDepression in diabetes results in a worse prognosis and quality of life, and increased costs to the patient and the healthcare system, yet remains largely underdiagnosed. We intend to evaluate the role of glucose variability (GV) indices as predictors of depressive symptoms (DS) in type 2 diabetes mellitus. Additionally, we aim to investigate the association between concomitant hypothyroidism in people with diabetes and depression; considering the pathophysiological ties between thyroid disorders and diabetes, and their influence on glycemic indices.MethodsOne hundred twenty-three people with diabetes were recruited from an outpatient endocrinology clinic and investigated for DS using the patient health questionnaire-9 (PHQ-9). To calculate GV indices, a total of 940 fasting blood sugar (FBS) and 793 hemoglobin-A1c (HbA1c) values were collected from the clinic visits of participants over the past 5 years. Additionally, a new composite index of GV was introduced to represent FBS and HbA1c variability together. Participants were screened for hypothyroidism and thyroid autoimmunity as well. The association of independent variables with PHQ-9 was investigated using linear and MM-estimation robust regression.ResultsForty-eight participants (39%) had a PHQ-9 score of >= 10. Twenty (16%) were classified as hypothyroid. The composite index of GV (beta = 0.17, p = 0.003), hypothyroidism (beta = 2.9, p = 0.037), and using insulin (beta = 5.4, p = 0.001) significantly correlated with the number of DS in the full regression model. The composite index performed better than previously reported GV indices in predicting DS. Thyroid autoimmunity did not correlate with depression. Findings were confirmed by robust regression.ConclusionIncreased GV, particularly a joint increase in FBS and HbA1c variability as represented by the composite index, can indicate a significant increase in DS that can be detected even in small-scale clinical settings. Concomitant hypothyroidism, although managed according to the guidelines, can still be a risk factor for depression in diabetes.