Introduction: While people with T1D report that blood glucose (BG) fluctuations affect their day-to-day functioning, these relationships are poorly understood. Using continuous glucose monitoring (CGM) , accelerometry, and momentary surveys and cognitive tasks, we sought to understand how various BG metrics during sleeping hours impact functioning the following day.

Methods: Participants wore a blinded CGM and accelerometer for 10-14 days, during which they completed surveys and cognitive tasks 5-6 times per day. Using dynamic structural equation modeling, we evaluated the within-person impact of overnight BG on the following day’s functioning, while controlling for the prior day’s functioning. BG variables included % time <70 mg/dL, % time >250 mg/dL, and coefficient of variation (CV) . Functioning variables included cognitive measures of sustained attention and perceptual speed; daily step count; and self-reported fatigue, task performance, and net activity demand.

Results: Among 127 adults with T1D (41±15 yrs, 46% male, 39% Latinx, 35% White, 10% Black, 4% Asian, 12% multiethnic/other) , all three BG variables predicted changes in next day functioning. More time <70 predicted poorer sustained attention (standardized b= -0.06) , while more time >250 predicted more fatigue (0.09) and lower step count (-0.12) (all p<0.05) . Higher CV had the broadest impact, predicting poorer sustained attention (-0.06) , more fatigue (0.05) , and less engagement in demanding activities (-0.05) (all p<0.05) .

Conclusion: Our findings indicate that overnight BG impacts cognition, physical activity, fatigue, and activity engagement the following day. While effect sizes are small, the cumulative impact of these decrements in function should be considered in the context of a life-long disorder. The consistent findings among diverse outcomes, including both objective and self-report measures, strengthen confidence in the overall conclusion that overnight BG has wide-ranging implications for functioning in adults with T1D.


E. Pyatak: Research Support; Abbott Diabetes. D. Spruijt-Metz: None. S. Schneider: None. J.P. Crandall: Research Support; Abbott Diabetes. A.L. Peters: Advisory Panel; Abbott Diabetes, AstraZeneca, Eli Lilly and Company, Novo Nordisk, Shouti, Vertex Pharmaceuticals Incorporated, Zealand Pharma A/S. Research Support; Abbott Diabetes, Dexcom, Inc., Insulet Corporation, Leona M. and Harry B. Helmsley Charitable Trust. Stock/Shareholder; Teladoc Health. Other Relationship; Omada Health, Inc. H. Jin: None. S. Agarwal: Advisory Panel; Medtronic. Consultant; Beta Bionics, Inc. L.T. Pham: None. A. Ali: None. C.J. Hoogendoorn: None. G. Crespo-Ramos: None. R. Basile: None. J.S. Gonzalez: Consultant; Virta Health Corp.


National Institutes of Health (1R01DK121298-01)

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