Objective: We aim to determine the association of the time-of-day of bout-related moderate-to-vigorous physical activity (bMVPA) with changes in glycemic control across 4 years in adults with overweight/obese and type 2 diabetes.
Research Design and Methods: Among 2416 participants (57% female; mean age, 59 years) with 7-day waist-worn accelerometry recording at year 1 or 4, we assigned bMVPA timing groups based on the participants’ temporal distribution of bMVPA at year 1, and recategorized them at year 4. The time-varying exposure of bMVPA (≥10-minute bout) timing was defined as ≥50% of bMVPA occurring during the same time period (Morning, Midday, Afternoon, or Evening), <50% of bMVPA in any time period (Mixed), and ≤1 day with bMVPA per week (Inactive).
Results: HbA1c reduction at year 1 varied among bMVPA timing groups (P=0.02), independent of weekly bMVPA volume and intensity. The afternoon group had the greatest HbA1c reduction (vs. Inactive: -0.22% [95%CI -0.39%, -0.06%]), the magnitude of which was 30%-50% larger than the other groups. The odds of discontinuation versus maintaining or initiating glucose-lowering medications at year 1 differed by bMVPA timing (P=0.04). The afternoon group had the highest odds (OR: 2.13 [1.29, 3.52]). For all the year-4 bMVPA timing groups, there were no significant changes in HbA1c between year 1 and 4.
Conclusion: bMVPA performed in the afternoon is associated with improvements in glycemic control in adults with diabetes, especially within the initial 12 months of an intervention. Experimental studies are needed to examine causality.
This study was funded by the National Heart, Lung, and Blood Institute (NHLBI) (K99-HL-148500, J.Q., principal investigator [PI]). Other funding for individual investigators includes NHLBI (R01-HL140574 to F.A.J.L.S.), NIA (RF1AG059867 and RF1AG064312 to K.H.) and NIDDK (K23-DK114550 to R.J.W.M.). The Look AHEAD study was supported by the Department of Health and Human Services through the following cooperative agreements from the NIH: DK57136, DK57149, DK56990, DK57177, DK57171, DK57151, DK57182, DK57131, DK57002, DK57078, DK57154, DK57178, DK57219, DK57008, DK57135, and DK56992. Additional funding was provided by the National Heart, Lung, and Blood Institute; National Institute of Nursing Research; National Center on Minority Health and Health Disparities; NIH Office of Research on Women’s Health; and the Centers for Disease Control and Prevention. This research was supported in part by the Intramural Research Program of the NIDDK. The Indian Health Service (IHS) provided personnel, medical oversight, and use of facilities. The opinions expressed in this paper are those of the authors and do not necessarily reflect the views of the IHS or other funding sources. Additional support was received from the Johns Hopkins Medical Institutions Bayview General Clinical Research Center (M01RR02719); the Massachusetts General Hospital Mallinckrodt General Clinical Research Center and the Massachusetts Institute of Technology General Clinical Research Center (M01RR01066); the University of Colorado Health Sciences Center General Clinical Research Center (M01RR00051) and Clinical Nutrition Research Unit (P30 DK48520); the University of Tennessee at Memphis General Clinical Research Center (M01RR0021140); the University of Pittsburgh General Clinical Research Center (GCRC) (M01RR000056), the Clinical Translational Research Center (CTRC) funded by the Clinical & Translational Science Award (UL1 RR 024153) and NIH grant (DK 046204); the VA Puget Sound Health Care System Medical