Hemoglobin A1c Variability Predicts Symptoms of Depression in Elderly Individuals With Type 2 Diabetes

Abstract

Objective: This study aimed to analyze the relationship of variability in hemoglobin A_1c (HbA_1c) over years with subsequent depressive symptoms.

Research design and methods: Subjects (n = 837) were participants of the Israel Diabetes and Cognitive Decline (IDCD) study, which aimed to examine the relationship of characteristics of long-term type 2 diabetes with cognitive decline. All pertain to a diabetes registry established in 1998, which contains an average of 18 HbA_1c measurements per subject. The results presented here are based on the IDCD baseline examination. Symptoms of depression were assessed using the 15-item version of the Geriatric Depression Scale (GDS). To quantify the association between variability in glycemic control (measured as the SD of HbA_1c measurements [HbA_1c-SD]) since 1998 with the number of depression symptoms at IDCD baseline, incidence rate ratios (IRRs) and corresponding 95% CIs were estimated via negative binomial regression modeling and used to account for the overdispersion in GDS scores.

Results: Subjects' ages averaged 72.74 years (SD 4.63 years), and the mean number of years in the diabetes registry was 8.7 (SD 2.64 years). The mean GDS score was 2.16 (SD 2.26); 10% of subjects had a GDS score ≥6, the cutoff for clinically significant depression. Mean HbA_1c significantly correlated with HbA_1c-SD (r = 0.6625; P < 0.0001). The SD, but not the mean, of HbA_1c measurements was significantly associated with the number of subsequent depressive symptoms. For each additional 1% increase in HbA_1c-SD, the number of depressive symptoms increased by a factor of 1.31 (IRR = 1.31 [95% CI 1.03-1.67]; P = 0.03).

Conclusions: Variability in glycemic control is associated with more depressive symptoms.