Exercise modes and their association with hypoglycemia episodes in adults with type 1 diabetes mellitus: a systematic review

OBJECTIVE: Type 1 diabetes mellitus rates are rising worldwide. The health benefits of physical exercise in this condition are many, but more than 60% do not participate, mainly from fear of hypoglycemia. This systematic review explores the effects of physical exercise modes on blood glucose levels in adults for hypoglycemia prevention. RESEARCH DESIGN AND METHODS: Predefined inclusion criteria were randomized or non-randomized cross-over trials of healthy non-obese adults with type 1 diabetes mellitus. Exercise interventions used standardized protocols of intensity and timing. Outcomes included hypoglycemia during or after exercise, and acute glycemic control. Medline, Cumulative Index to Nursing and Allied Health Literature, Allied and Complementary Medicine Database, SPORTDiscus, CochraneCENTRAL (1990 to 11 January 2018), and Embase (1988 to 9 April 2018) were searched using keywords and Medical Subject Heading (MeSH) terms. Inclusions, data extraction and quality assessment using the Critical Appraisal Skills Programme checklists were done by one researcher and checked by a second. Review Manager (V.5.3) was used for meta-analysis where four or more outcomes were reported. RESULTS: From 5459 citations, we included 15 small cross-over studies (3 non-randomized), 13 assessing aerobic (intermittent high-intensity exercise (IHE) vs continuous, or continuous vs rest) and 2 assessing resistance exercise versus rest. Study quality was good, and all outcome measures were reported. Thirteen gave hypoglycemia results, of which five had no episodes. Meta-analysis of hypoglycemia during or after IHE compared with continuous exercise showed no significant differences (n=5, OR=0.68 (95% CI 0.16 to 2.86), I(2)=56%). For blood glucose there was little difference between groups at any time point. CONCLUSION: IHE may be safer than continuous exercise because of lesser decline in blood glucose, but more research needs to demonstrate if this would be reflected in hypoglycemic episode rates. TRIAL REGISTRATION NUMBER: CRD42018068358.