Abstract
Aim: Patients with Type 2 Diabetes Mellitus (T2DM) have increased risk of developing vascular complications due to chronic hyperglycemia. Glycemic variability (GV) has been suggested to play an even more important role in the risk of developing diabetic complications than sustained hyperglycemia. Physical activity (PA) has shown reducing effects on mean plasma glucose; however, the effect on GV in T2DM needs further description. The objective of this review is to evaluate the effect of PA on GV, assessed by continuous glucose monitoring (CGM) in people with T2DM.Methods: A systematic literature search was conducted on MEDLINE and Embase to find randomized controlled trials (RCTs) covering the aspects T2DM, PA, and CGM. Following eligibility screening, variables of population characteristics, PA interventions, and GV outcomes were extracted and processed through qualitative synthesis. Risk of bias (ROB) was assessed using Cochrane ROB tool v2.0.Results: Of 1,825 identified articles, 40 full texts were screened. In the ten included RCTs matching the eligibility criteria, sample sizes ranged from nine to 63, mean age from 51 (SD 11) to 65 (SD 2) years and mean T2DM duration from four (SD 3) to ten (SD 6) years. Eight RCTs examined GV following single bouts of exercise, while two RCTs examined GV following training interventions. One RCT applied parallel group design, while nine RCTs applied crossover design. Numeric reductions in GV following acute exercise were seen, with four RCTs reaching statistical significance. Numeric reductions in GV were seen following training interventions, with one RCT reaching statistical significance. Numeric reductions of GV after PA appeared independently of intensity and T2DM progression but higher in participants with high baseline HbA1c and GV than with low. 80% of the trials were evaluated as uncertain/high ROB.Conclusion: The systematic literature search revealed limited and biased evidence showing that acute PA numerically reduced GV in patients with T2DM. PA reduced GV independently of PA intensity and T2DM progression. Prolonged RCTs with low ROB are needed to confirm reducing effects of PA on GV and to assess the influence of patient- and intervention characteristics on the effect of PA on GV.
Highlights
Type 2 diabetes mellitus (T2DM) is characterized by increasing insulin resistance concurrent with a not fully compensatory increase in insulin secretion from the pancreatic beta-cells, resulting in pathological hyperglycemia (1)
The systematic reviewed literature revealed a limited body of evidence examining the effect of physical activity (PA) on CGM derived measures of GV in patients with T2DM, especially for prolonged engagement in exercise interventions
The beneficial reducing effect of acute exercise on GV was attenuated when adjusting for mean glucose
Summary
Type 2 diabetes mellitus (T2DM) is characterized by increasing insulin resistance concurrent with a not fully compensatory increase in insulin secretion from the pancreatic beta-cells, resulting in pathological hyperglycemia (1). It is well-known that patients with T2DM have increased risk of developing micro- and macrovascular diabetic complications (2). The measurement of HbA1c reflects the mean plasma glucose level during the last 2–3 months prior to testing and is currently the primary target in the clinical management of hyperglycemia in T2DM (3) It represents a convenient laboratory test, which is not crucially affected by dietary and physical activity behavior immediately prior to testing (7). Increased mean plasma glucose levels are strongly associated with microvascular diabetic complications (2) whereas the association between mean plasma glucose levels and macrovascular complications is less straight forward (8)
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