Abstract
OBJECTIVE: Despite established relationships between glycemia and cognition, few studies have evaluated within-person changes over time. We paired continuous glucose monitoring (CGM) with ambulatory cognitive testing to examine bidirectional associations among adults with type 1 diabetes (T1D). RESEARCH DESIGN AND METHODS: Participants wore blinded CGM and completed ambulatory tests of perceptual speed and sustained attention five or six times daily for 14 days. CGM metrics were calculated over 3-h periods (mean glucose, %time in range [70-180 mg/dL], %time in low [<70 mg/dL], %time in high [181-250 mg/dL], %time in very high [>250 mg/dL], and coefficient of variation). Immediate glucose values within 15 min of cognitive assessments were also examined. Dynamic structural equation models evaluated bidirectional relationships over sequential 3-h periods. RESULTS: Among 182 diverse adults with T1D (age 40 ± 14 years, 46% male, 41% Latino, 29% White, 15% Black), more time in low glucose over 3 h was associated with slower perceptual speed at the end of that interval (P < 0.05) but not 3 h later. More time in high glucose (>250 mg/dL) was associated with faster perceptual speed initially but slower speed 3 h later (P < 0.05). Physical activity partially mediated the effect of high glucose on slower perceptual speed. Glycemia did not predict attention scores within persons. Lower attention and higher perceptual speed predicted higher mean glucose and more time in very high glucose over the following 3 h (P < 0.05). CONCLUSIONS: These novel observations of significant bidirectional association between glycemia and cognitive performance over the course of the day among adults with T1D emphasize the importance of examining within-person longitudinal effects over different time frames.