Long-term Glycemic Variability and Risk of Adverse Outcomes: A Systematic Review and Meta-analysis

OBJECTIVE Glycemic variability is emerging as a measure of glycemic control, which may be a reliable predictor of complications. This systematic review and meta-analysis evaluates the association between HbA 1c variability and micro- and macrovascular complications and mortality in type 1 and type 2 diabetes. RESEARCH DESIGN AND METHODS Medline and Embase were searched (2004–2015) for studies describing associations between HbA 1c variability and adverse outcomes in patients with type 1 and type 2 diabetes. Data extraction was performed independently by two reviewers. Random-effects meta-analysis was performed with stratification according to the measure of HbA 1c variability, method of analysis, and diabetes type. RESULTS Seven studies evaluated HbA 1c variability among patients with type 1 diabetes and showed an association of HbA 1c variability with renal disease (risk ratio 1.56 [95% CI 1.08–2.25], two studies), cardiovascular events (1.98 [1.39–2.82]), and retinopathy (2.11 [1.54–2.89]). Thirteen studies evaluated HbA 1c variability among patients with type 2 diabetes. Higher HbA 1c variability was associated with higher risk of renal disease (1.34 [1.15–1.57], two studies), macrovascular events (1.21 [1.06–1.38]), ulceration/gangrene (1.50 [1.06–2.12]), cardiovascular disease (1.27 [1.15–1.40]), and mortality (1.34 [1.18–1.53]). Most studies were retrospective with lack of adjustment for potential confounders, and inconsistency existed in the definition of HbA 1c variability. CONCLUSIONS HbA 1c variability was positively associated with micro- and macrovascular complications and mortality independently of the HbA 1c level and might play a future role in clinical risk assessment.