Overnight glucose associated with next-day functioning in adults with type 1 diabetes

More variation in overnight glucose levels and time spent above and below glucose targets were associated with adverse changes in measures of next-day function, including attention, sedentary time, and engagement in demanding activities, a study found.

Overnight glucose fluctuations may cause adverse effects on physical activity and cognition the following day in adults with type 1 diabetes, a recent study found.

From June 2020 to February 2022, researchers recruited participants from the patient populations of two large health systems in Los Angeles and the Bronx in New York City. Eligible participants were adults who had type 1 diabetes for at least one year and were on a stable treatment regimen for diabetes and any other medical conditions. After enrollment, they received mailed study materials, including an accelerometer, blinded continuous glucose monitor (CGM), and smartphone preloaded with an ecological momentary assessment (EMA) survey application and mobile cognitive tasks. Patients underwent 14 days of data collection, taking EMA surveys and performing cognitive tasks five to six times per day at three-hour intervals. The researchers used dynamic structural equation modeling to examine whether overnight glucose levels (coefficient of variation [CV], percent time <70 mg/dL [3.9 mmol/L], and percent time >250 mg/dL [13.9 mmol/L]) were associated with seven next-day functioning measures (sustained attention, perceptual speed, percentage of time sedentary, step count, self-reported function, net demand daily activities, and task load). Results were published March 2 by Diabetes Care.

Of 196 participants who started the study protocol, 12 had no readable CGM data and 21 had fewer than seven days of concurrent EMA and CGM data, leaving 166 participants (mean age, 41 years; 54.8% female). On average, participants contributed about 13 days of data, for a total sample size of 2,151 days. Overnight CV (P=0.017) and percentage of time above 250 mg/dL (13.9 mmol/L) (P=0.037) significantly predicted overall next-day functioning. Pairwise tests indicated that higher CV was associated with poorer sustained attention (P=0.028) and lower engagement in demanding activities (P=0.028), that time below 70 mg/dL (3.9 mmol/L) was associated with poorer sustained attention (P=0.007), and that time above 250 mg/dL (13.9 mmol/L) was associated with more sedentary time (P=0.024). Greater sleep fragmentation partially accounted for the negative effect of glucose variability on sustained attention. Individual differences were also noted, for example, patients in whom overnight time below 70 mg/dL (3.9 mmol/L) was associated with worse sustained attention reported more illness intrusiveness (P=0.016) and lower diabetes-related quality of life (P=0.036).

The study's observational design precludes making strong causal inferences, the authors noted. They added that since the analysis focused on the association of overnight glucose and daily functioning, there may be undetected within-day or longer-term effects of glucose on functioning, among other limitations.

“While the observed decrements in function are small, their significance is magnified when considering their cumulative impact over a lifetime,” the authors wrote. “Individualizing treatment and using diabetes technologies to minimize overnight glucose fluctuations have the potential to enhance function and quality of life for adults with type 1 diabetes.”