Optimal type and dose of exercise to improve glycated haemoglobin in individuals with type 1 diabetes: A systematic review and Bayesian dose-response network meta-analysis of RCTs.

Background: High levels of glycated haemoglobin (HbA1c) in people with type 1 diabetes (T1D) are associated with high mortality and cardiovascular risk. Physical activity is an affordable intervention that is available to most people, but the type and amount of exercise to induce metabolic benefits in T1D are not known with certainty.

Objective: To determine the comparative effectiveness of diverse exercise modes and dosages to influence HbA1c in patients with T1D.

Methods: The process involved systematically searching PubMed, Web of Science, Embase and The Cochrane Library databases; no limits were imposed on date or language of publication. Bayesian network and dose-response meta-analyses based on a random-effects model were carried out to assess the impact of exercise on the HbA1c levels.

Results: Nineteen studies were included in the systematic review. Only multi-component exercise (ME) significantly reduced HbA1c (-0.81%, 95% CrI: -1.33 to -0.34; SUCRA: 93.75%; low-quality evidence). High-intensity interval training (-0.38%, 95% CrI: -1.16 to 0.39; SUCRA: 51.52%) and aerobic exercise (-0.31%, 95% CrI: -0.74 to 0.16; SUCRA: 47.01%) showed no significant benefit. For ME, an L-shaped non-linear dose-response was observed, with statistical significance at 52 metabolic equivalent of task (MET-min/week) and the minimal clinically important difference (MCID; ≥ 0.5% reduction) achieved at 160 MET-min/week (-0.52%, 95% CrI: -0.89 to -0.13). The greatest reduction occurred at 1500 MET-min/week (-0.82%, 95% CrI: -1.31 to -0.27).

Conclusions: A dose of ME necessary to achieve MCID (e.g., 10 min of running and curl-ups, three times per week) was well below the American Diabetes Association's minimum recommendation. For adolescents, we recommend combining aerobic and resistance training, performed for at least 12 weeks with 160 to 1200 MET-min/week (equivalent to 25-220 min per week), to balance effectiveness and minimise exercise burden. The high-quality randomized controlled trials of this dose range are required to confirm efficacy and evaluate safety.