The effect of time spent outdoors during summer on daily blood glucose and steps in women with type 2 diabetes
This study investigated changes in glycemic control following a small increase in time spent outdoors. Women participants with type 2 diabetes (N = 46) wore an iBUTTON temperature monitor and a pedometer for 1 week and recorded their morning fasting blood glucose (FBG) daily. They went about their normal activities for 2 days (baseline) and were asked to add 30 min of time outdoors during Days 3–7 (intervention). Linear mixed effects models were used to test whether morning FBG values were different on days following intervention versus baseline days, and whether steps and/or heat exposure changed. Results were stratified by indicators of good versus poor glycemic control prior to initiation of the study. On average, blood glucose was reduced by 6.1 mg/dL (95% CI − 11.5, − 0.6) on mornings after intervention days after adjusting for age, BMI, and ambient weather conditions. Participants in the poor glycemic control group (n = 16) experienced a 15.8 mg/dL decrease (95% CI − 27.1, − 4.5) in morning FBG on days following the intervention compared to a 1.6 mg/dL decrease (95%CI − 7.7, 4.5) for participants in the good glycemic control group (n = 30). Including daily steps or heat exposure did not attenuate the association between intervention and morning FBG. The present study suggests spending an additional 30 min outdoors may improve glycemic control; however, further examination with a larger sample over a longer duration and determination of mediators of this relationship is warranted.
KeywordsT2DM Diabetes Fasting glucose Time spent outdoors Ambient temperature Physical activity
Special thanks to the participants and community partners Ethel Johnson, Sheryl-Threadgill Matthews, Sheila Tyson, Keisha Brown, Clarice Davis, and Emily Ingram. All authors certify that they have participated sufficiently in the work. Funding was provided by National Institute of Environmental Health Sciences (Grant No. R01ES023029).
Compliance with ethical standards
Conflict of interest
Molly B. Richardson, Courtney Chmielewski, Connor Y. H. Wu, Mary B. Evans, Leslie A. McClure, Kathryn W. Hosig and Julia M. Gohlke declare that they have no conflict of interest.
Human and animal rights and Informed consent
All procedures followed were in accordance with ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000. Informed consent was obtained from all participants prior to inclusion in the study.
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