Adults with type 1 diabetes had significantly better glycemic control on days they exercised, regardless of exercise type, compared to days when they were inactive, according to a prospective study in nearly 500 individuals.
Different types of exercise, such as aerobic workouts, interval training, or resistance training, may have different immediate glycemic effects in adults with type 1 diabetes (T1D), but the impact of exercise type on the percentage of time diabetes patients maintain glucose in the 70-180 mg/dL range on days when they are active vs. inactive has not been well studied, Zoey Li said in a presentation at the annual scientific sessions of the American Diabetes Association.
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In the Type 1 Diabetes Exercise Initiative (T1DEXI) study, Ms. Li and colleagues examined continuous glucose monitoring (CGM) data from 497 adults with T1D. The observational study included self-referred adults aged 18 years and older who had been living with T1D for at least 2 years. Participants were assigned to programs of aerobic exercise (defined as a target heart rate of 70%-80% of age-predicted maximum), interval exercise (defined as an interval heart rate of 80%-90% of age-predicted maximum), or resistance exercise (defined as muscle group fatigue after three sets of eight repetitions).
Participants completed the workouts at home via 30-minute videos at least six times over the 4-week study period. The study design involved an activity goal of at least 150 minutes per week, including the videos and self-reported usual activity, such as walking. The data were collected through an app designed for the study, a heart rate monitor, and a CGM.
The researchers compared glucose levels on days when the participants reported being active compared to days when they were sedentary. The goal of the study was to assess the effect of exercise type on time spent with glucose in the range of 70-180 mg/dL, defined as time in range (TIR).
The mean age of the participants was 37 years; 89% were White. The mean duration of diabetes was 18 years, and the mean hemoglobin A1c was 6.6%. “An astounding 95% were current continuous glucose monitoring [CGM] users,” said Ms. Li, a statistician at the Jaeb Center for Health Research in Tampa, Fla.
A total of 398 participants reported at least one exercise day and one sedentary day, for a total of 1,302 exercise days and 2,470 sedentary days.
Overall, the mean TIR was significantly higher on exercise days compared to sedentary days (75% vs. 70%, P < .001). The median time above 180 mg/dL also was significantly lower on exercise days compared to sedentary days (17% vs. 23%, P < .001), and mean glucose levels were 10 mg/dL lower on exercise days (145 mg/dL vs. 155 mg/dL)
“This all came with a slight hit to their time below range,” Ms. Li noted. The median time below 70 mg/dL was 1.1% on exercise days compared to 0.4% on sedentary days (P < .001). The percentage of days with hypoglycemic events was higher on exercise days compared to sedentary days (47% vs. 40%, P < .001), as they are related to time below 70 mg/dL, she added.
The differences for mean glucose level and TIR between exercise days and sedentary days were significant for each of the three exercise types, Ms. Li said.
“After establishing these glycemic trends, we looked at whether there were any factors that influenced the glycemic differences on exercise vs. sedentary days,” Ms. Li said.
Regardless of exercise type, age, sex, baseline A1c, diabetes duration, body mass index, insulin modality, CGM use, and percentage of time below range in the past 24 hours, there was higher TIR and higher hypoglycemia on exercise days compared to sedentary days.
Although the study was limited in part by the observational design, “with these data, we can better understand the glycemic benefits and disadvantages of exercise in adults with type 1 diabetes,” Ms. Li said.