Longitudinal trajectories and predictors of glycated hemoglobin among type 2 diabetes patients concomitant with hypertension: spline based linear mixed-effects model

Monitoring glycated hemoglobin biomarkers is very essential to be early aware of that metabolic abnormality and poorly controlled blood sugar. The presence of type 2 diabetes has been associated with an increased risk of hypertension and vice versa, and their coexistence increases the risk of micro and macro-complications and poor glycemic control. The aim of the study is to assess HbA1c trajectories and identify its predictors among type 2 diabetes patients concomitant with hypertension. An institution-based retrospective follow-up study was conducted at Debre Markos Comprehensive and Specialized Hospital. A total of 648 were sampled, and 600 were included in the final analysis among type 2 diabetes patients concomitant with hypertension between June 30, 2014, and July 01, 2023. The best time function, covariance structure, and model comparison were conducted, and those that had the lowest AIC and/or BIC were selected. A linear mixed-effects model with cubic natural spline random intercepts and slopes has been constructed to model the complete true history of HbA1c for each subject by considering the effects of baseline covariates and socio-demographic factors on HbA1c evolution. Finally, statistical significance was declared at 95% CI with a P-value less than 0.05. Patients were followed for different follow-up times, with a median follow-up period of 85.2 months (IQR: 25.1). Injection medication (β = − 0.16, 95% CI: [− 0.29, − 0.02]) and treatment duration >  = 6 years (β = − 0.12, 95% CI: [− 0.21, − 0.03]) were associated with lower HbA1c level, while obesity (β = 0.12, 95% CI: [0.01, 0.22]), presence of nephropathy (β = 0.35, 95% CI: [0.25, 0.51]), higher weight (β = 0.09, 95% CI: [0.01, 0.21]), uncontrolled hypertension (β = 0.89, 95% CI: [0.23, 1.14]), and family history of diabetes (β = 0.22, 95% CI: [0.12, 0.36]) were associated with higher biomarker level. The mean glycated hemoglobin was high when compared to the American Diabetes Association. This study revealed that injection medication, obesity, presence of nephropathy, higher weight, family history of diabetes, uncontrolled hypertension, and ≥ 6 years of treatment duration were significant predictors of HbA1c level. Therefore, prioritize patients with uncontrolled hypertension and any other comorbidity, and integrating weight management into a routine system for risk assessment and glycemic control is highly recommended.