This study evaluated a new metric called Glycemia Risk Index (GRI) for assessing glucose levels in people with type 1 diabetes (T1D) on days where they exercise versus sedentary days (when no exercise occurs). Current glucose monitoring methods don’t adequately account for extreme high or low glucose levels, which can lead to an underestimation of the risk of hypoglycemia as a result of exercise.

The study used data from the previously published “T1DEXI” dataset which involved 408 adults who wore continuous glucose monitors (CGMs) and activity trackers for four weeks. Exercise days were defined as any 24-hour period following at least 20 minutes of exercise, while sedentary days had no recorded exercise. Despite exercise being a well known risk factor for hypoglycemia, it was found that GRI was lower on exercise days compared to sedentary days, indicating a ~5% reduction in risk of hypoglycemia on exercise days. The GRI showed improvement on exercise days, despite the increase in time below range, due to the large effect of exercise on time above range. The benefit of exercise was greatest in those with the sub-optimal baseline glucose control, and the risk of hypoglycemia was not increased in those who spent the most time below their target blood glucose range. Overall, exercise helped participants to increase their time in the target glucose range, reduced time above this range, and slightly increased time below the range on days when they exercised.

Overall, despite an increase in time below range (ie. hypogylcaemia) which is typically associated with the greatest “risk” of a hypoglycemic episode, exercise still improved GRI in people with T1D. This occurred because there was a proportionally greater decrease in their time above range as a result of exercising. This study concluded that GRI improved on days where exercise occurs in comparison to sedentary days and emphasizes that exercise should be a priority for all people with T1D.