Background: Hypoglycemia is the most common and serious side effect of insulin therapy in type 1 diabetes (T1DM), frequently occurring both during and after vigorous exercise. Late-onset hypoglycemia (LOH) is of great concern, occurring 1-36 h after exercise, often going unnoticed during sleep. Repeated exposure to LOH causes autonomic glucose counterregulatory failure and sometimes coma and death. Continuous glucose monitoring systems have recently emerged as a potentially important tool in diabetes management, allowing individuals to track glucose levels continuously and learn how various behaviors influence glucose control.
Methods: In this pilot study, we determined the efficacy of using a real-time continuous glucose monitoring system (Guardian RT, Minimed, Northridge, CA) to detect blood glucose excursions associated with exercise and LOH (i.e., blood glucose concentration <4 mM) after exercise in individuals with T1DM. Five subjects with T1DM were monitored before, during, and after a 60 min vigorous spin class using Guardian RT (48 h in total).
Results: Following the exercise, three of the five subjects had LOH, while the other two experienced decreases in blood glucose concentrations to 4 mM. The Guardian RT monitor was effective in notifying all of the subjects of such glycemic excursions over the 48 h surveillance period. A strong correlation (r = 0.89, P < 0.001) was found between conventional self-monitoring of blood glucose and Guardian RT data pairs.
Conclusion: These limited data suggest that nocturnal LOH occurs commonly following vigorous exercise and that a Guardian RT is a useful and important diagnostic tool. Further study into clinical strategies for preventing hypoglycemia associated with this common form of mixed aerobic and anaerobic exercise is urgently needed through insulin modification and carbohydrate supplementation.