Delayed effect of different exercise modalities on glycaemic control in type 1 diabetes mellitus: a systematic review and meta-analysis

Abstract Background and Aims Despite the crucial role of exercise in the prevention of comorbidities and complications in type 1 diabetes mellitus (T1DM), people living with the disease are often insufficiently physically active, mainly due to the fear of hypoglycaemia. Research using continuous glucose monitoring (CGM) devices has shown that exercise affects glycaemic control in T1DM for over 24 hours. The aim of this systematic review and meta-analysis is, therefore, to investigate the delayed effects of different exercise modalities on glycaemic control in adults with T1DM. Methods and Results The literature search of experimental studies was conducted on PubMed, SPORTDiscus and EMBASE from January 2000 to September 2019. Twelve studies using CGM devices were included. Compared to endurance, intermittent exercise increased the time spent in hypoglycaemia (0.62, 0.07 to 1.18; standardised effect size, 95% CI) and reduced the mean interstitial glucose concentration (-0.88, -1.45 to -0.33). No differences emerged in the time spent in hyperglycaemia (-0.07, -0.58 to 0.45) or in the proportion of exercisers experiencing hypoglycaemic events (0.82, 0.45 to 1.49; proportion ratio, 95% CI) between conditions. The systematic review also found a reduced risk of hypoglycaemia if exercise is performed in the morning rather than in the afternoon, and with a 50% rapid-acting insulin reduction. It was not possible to determine the benefits of resistance exercise. Conclusions For the first time, we systematically investigated the delayed effect of exercise in adults with T1DM, highlighted undetected effects, shortcomings in the existing literature, and provided suggestions to design future comparable studies.