IMPACT clinical trial data

Importance: The efficacy of physical activity interventions among individuals with type 2 diabetes has been established; however, practical approaches to translate and extend these findings into community settings have not been well explored.

Objective: To test the effectiveness of providing varying frequencies of weekly structured exercise sessions to improve diabetes control.

Design: The IMPACT study was a randomized controlled clinical trial (randomization: October 2016 to April 2019) that included a 6-month, structured exercise intervention either once or thrice-weekly versus usual care (advice only). Statistical analysis was performed in 2022.

Setting: The exercise intervention was conducted at community-based fitness centers. Follow-up visits were conducted in a university research clinic.

Participants: Participants included 357 adults with type 2 diabetes (HbA1c 6.5-13.0%, not taking insulin, no precluding health issues).

Interventions: 119 participants were randomized to the usual care (UC) group, 119 to the once-weekly structured exercise group, and 119 to the thrice-weekly structured exercise group.

Main Outcomes and Measures: The primary outcome was HbA1c at 3 and 6 months.

Results: 357 participants with mean age of 57.4 (SD 11.1) years and 40.1% females were randomized. No difference in HbA1c change was observed by study group in the intention-to-treat (ITT) analysis (P=.17). 54.6% of the once-weekly group and 48.7% of the thrice-weekly group were at least 50% adherent to the assigned structured exercise regimen. Per-protocol analysis (PP) showed HbA1c was lower by 0.35% (95% CI, 0.10% – 0.60%) at 3 months (P=.005) and by 0.38% (95% CI, 0.12% – 0.65%) at 6 months in the thrice-weekly group compared to UC (P=.005), with no statistically significant decrease in HbA1c in the once-weekly group. The exercise intervention was effective in improving self-reported MET min/week for participants in the thrice-a-week structured exercise program (both overall and in PP).

Conclusions and Relevance: Only participants in the thrice-weekly structured exercise group who attended at least 50% of the sessions during the 6-month exercise intervention program improved HbA1c levels at 3 and 6 months. No statistically significant improvement in HbA1c was observed among participants in UC or the once-weekly structured exercise group, in either ITT or PP.