Retinopathy and nephropathy in type 1 diabetes: role of HbA1c and blood pressure variability.

Aims: To examine the association between within-person variability in glycated hemoglobin A1c (HbA1c) and blood pressure (BP) with retinopathy and nephropathy in type 1 diabetes (T1D).

Methods: This nationwide cohort included 9,358 individuals from the Swedish National Diabetes Register with T1D <5 years at inclusion (1998-2017) and ≥8 years follow-up. Variability in HbA1c, systolic BP (SBP), and diastolic BP (DBP) was calculated as updated SDs. Associations with microvascular complications were analyzed using logistic regression with generalized estimating equations, adjusted for demographic and clinical covariates.

Results: Mean age at inclusion was 14.2 years, mean diabetes duration 1.2 years, and 44% were female. Over 10.7 years' follow-up, retinopathy developed in 33% and nephropathy in 9.3%. SBP variability was significantly associated with pre-proliferative or proliferative retinopathy (aOR 1.13, 95% CI 1.00-1.27) and proliferative retinopathy/ laser photocoagulation (1.23, 1.04-1.45), as well as with any albuminuria (1.15, 1.08-1.23) and macroalbuminuria (1.29, 1.15-1.45). DBP variability was associated with any albuminuria (1.11, 1.03-1.19) and macroalbuminuria (1.28, 1.10-1.50). HbA1c variability was associated with any retinopathy (1.14, 1.08-1.20) and any albuminuria (1.12, 1.03-1.21).

Conclusions: Beyond mean levels, higher variability in HbA1c and BP is associated with retinopathy and nephropathy. Stable BP control in patients with established retinopathy may be important to prevent progression to sight-threatening stages.