The effects of physical activity and nutrition interventions on glycated haemoglobin (HbA1c) in adolescents with type 1 diabetes mellitus: A systematic review with meta-analysis

Summary: Aims: This review investigates the effectiveness of physical activity and nutrition interventions on glycated haemoglobin (HbA1c) in adolescents with Type 1 Diabetes Mellitus (T1D). Methods: This review was conducted in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Databases (PsycInfo, Medline, CINAHL complete, Embase, Cochrane Library) and trial registries were searched from 2008. Inclusion criteria included adolescents aged between 10 and 19 years with a diagnosis of T1D, interventional studies involving physical activity and/or nutrition intervention, and HbA1c included as an outcome measure. Information about the studies, participants and outcome measures were extracted from the included studies. The risk-of-bias was performed using Cochrane risk-of-bias 2 tool (ROB-2) and risk-of-bias non-randomized intervention studies (ROBINS-I) tool. The certainty of evidence was assessed using ‘Grading of Recommendations Assessment, Development and Evaluation’ (GRADE) guidance. A meta-analysis was carried out to evaluate the effectiveness of these interventions on HbA1c. Results: The twelve eligible randomised controlled trials included 680 participants in total (of which 658 were diagnosed with T1D). HbA1c for adolescents with T1D at baseline was between 6.9-11%. There was no statistically significant evidence of effect noted for physical activity interventions (6 studies, 362 participants, mean difference -0.40, 95% confidence interval -0.88, 0.08; P = 0.11) or nutrition interventions (5 studies, 224 participants, mean difference -0.05, 95% confidence interval -0.31, 0.21; P = 0.71). Moderate heterogeneity was reported for physical activity (Chi2 10.48, P = 0.06), I2=52%) and nutrition interventions (Chi2 15.59, P = 0.004, I2=74%). There was a high risk of bias for two studies and ‘some concerns’ for six studies. Conclusions: While no statistically significant pooled effects on HbA1c were observed for physical activity or nutrition interventions, most confidence intervals trended toward lower HbA1c, suggesting potential for clinically meaningful benefit. Combined interventions showed signals of HbA1c reduction in small studies, but evidence remains limited and heterogeneous. Overall certainty was low, highlighting the need for robust trials of structured, combined interventions in adolescents.