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High Altitudes Could Influence Hypoglycemia Risk After Exercise in Type 1 Diabetes

A trial comparing changes in blood glucose before, during, and after exercise at sea level and simulated altitude provides insight into the potential increase in risk for hypoglycemia among patients with type 1 diabetes.

New research from investigators at the University of Western Australia suggests patients with diabetes may need to monitor their blood glucose levels more closely in high-altitude settings.

Performed with an interest in studying the effects of acute hypoxia on blood glucose level, results of the investigators’ study suggest physical activities at elevated altitudes suggests being under hypoxic conditions contribute to significantly lower blood glucose levels during recovery after exercise compared to both pre-exercise levels and normoxic conditions

“These findings suggest that exercise performed shortly after exposure to high altitude may increase the risk of exercise-mediated hypoglycemia,” said Cory Dugan, AFHEA, BSc, of the University of Western Australia, in a statement. “We ask that future guidelines consider these findings to increase the safety of people with type 1 diabetes when traveling from low to high altitude areas like the mountains without any acclimatization.”

Citing an apparent gap related to current guideline recommendations for exercise in patients with type 1 diabetes at high altitude, Dugan and a team of colleagues conducted a counterbalanced, repeated measures study to assess the effects of acute hypoxia on blood glucose levels and carbohydrate oxidation rates during bouts of moderate-intensity exercise. A total of 7 patients with type 1 diabetes were enrolled and these patients underwent 2 exercise sessions, at normoxic and simulated hypoxic conditions.

Exercise sessions consisted of 60 minutes of cycling on an ergometer at 45% of the participant’s sea-level peak Vo2 and then recovered for a 60-minute period. Before, during, and after exercise, blood samples were taken to measure glucose, lactate, and insulin levels. Investigators noted respiratory gases were collected to assess carbohydrate oxidation rates.

Upon analysis, data from the study indicated there was no drop in blood glucose level during the first 30 minutes of exercise in either condition. After an hour of exercise and during recovery, results suggested blood glucose levels were significantly lower when under hypoxic conditions compared to both pre-exercise levels (P=.008) and when under normoxic conditions (P=.027).

When assessing carbohydrate oxidation rates, results demonstrated exercise in both conditions resulted in a significant rise in oxidation rates, which returned to baseline levels following exercise. Investigators pointed out carbohydrate oxidation rates were higher under hypoxic conditions compared to normoxic conditions before, during, and after exercise.

“The greater decline in blood glucose level during and after exercise performed under acute hypoxia suggests that exercise during acute exposure to high altitude may increase the risk of hypoglycemia in individuals with T1D. Future guidelines may have to consider the impact altitude has on exercise-mediated hypoglycemia,” wrote investigators.

This study, “Effects of simulated high altitude on blood glucose levels during exercise in individuals with Type 1 Diabetes,” was published in the Journal of Clinical Endocrinology & Metabolism.