Transient Cognitive Vulnerability After Hypoglycemia in Adults With Type 1 Diabetes: Evidence From Continuous Glucose Monitoring and Cognitive Ecologic Momentary Assessment

OBJECTIVE Adults with type 1 diabetes experience short-term changes in cognitive performance after glycemic events; however, the duration of such cognitive effects remains unclear. We examined whether hypoglycemic and hyperglycemic events and rapid glucose changes were associated with changes in processing speed or sustained attention in adults with type 1 diabetes and whether these associations varied by time since the event. RESEARCH DESIGN AND METHODS Participants (N = 190) completed 15 days of smartphone-based ecologic momentary assessment (EMA; 3 prompts/day) paired with continuous glucose monitoring. Cognitive performance (median reaction time and accuracy) was tested using digit symbol matching (DSM) and gradual-onset continuous performance testing (GCPT; sustained attention) by TestMyBrain (processing speed). Glycemic exposures were defined as hypoglycemia or hyperglycemia lasting ≥15 min and rapid (5-min) increases or decreases in glucose >15 mg/dL, occurring during nonoverlapping intervals: 0–1, 1–2, and 2–3 h before EMA. Multilevel models estimated associations between glycemic exposures and cognitive performance, adjusting for age, EMA count, and interruptions. RESULTS Hypoglycemic events occurring within 0–1 h of EMA were associated with slower reaction time and poorer performance on DSM and GCPT. No associations were observed for events occurring 1–2 or 2–3 h before EMA. Hyperglycemic events and rapid glucose increases or decreases were not associated with cognition across most outcomes or time windows. CONCLUSIONS Hypoglycemia was associated with a transient period of cognitive vulnerability largely confined to the hour after an event, with little evidence of delayed effects. Findings support avoiding or exercising caution during cognitively demanding tasks for up to an hour after a hypoglycemic event. ARTICLE HIGHLIGHTS Why did we undertake this study? Short-term cognitive fluctuations are common among adults with type 1 diabetes; however, whether they reflect immediate or lingering effects of prior glycemic events remains unclear. What is the specific question(s) we wanted to answer? We examined whether glycemic events and rapid glucose changes were associated with processing speed or sustained attention and whether the associations varied by time since the event. What did we find? Hypoglycemic events occurring within the preceding hour of assessment were associated with slower reaction time and poorer cognitive performance. No associations were observed for events occurring 1–3 h before assessment. What are the implications of our findings? Cognitive vulnerability after hypoglycemic events seems transient and limited largely to the first hour after an event, supporting caution when engaging in cognitively demanding tasks during that time.