Glycaemic variation and atrial fibrillation burden and progression in individuals without diabetes undergoing continuous rhythm monitoring

BACKGROUND: Glycaemic dysregulation is associated with clinically diagnosed atrial fibrillation (AF), but prior studies have largely relied on limited monitoring of heart rhythm and glucose levels. We investigated whether periods with higher glucose exposure were associated with AF burden and progression in individuals undergoing long-term continuous monitoring and serial haemoglobin A1c (HbA1c) measurements. METHODS: Post-hoc analysis of 884 LOOP Study participants without diabetes undergoing implantable loop recorder (ILR) screening for AF and repeated HbA1c measurements. AF burden, defined as percentage of time in AF, was calculated in the 60-days prior to blood sampling and analysed in groups by highest HbA1c level and using a two-part mixed-effects model, while AF progression was assessed by cumulative AF duration and burden over time. RESULTS: The dataset combined >1 million days of heart rhythm monitoring (including 34,852 with AF) with 3079 HbA1c measurements. The AF burden was 0.52% [0.09-3.45%], 0.78% [0.25-4.07%], and 4.42% [0.98-13.1%], for HbA1c measurements in the normal (≤38 mmol/mol), prediabetic (39-47 mmol/mol), and diabetic (≥48 mmol/mol) range, respectively. A 1 mmol/mol increase in HbA1c was associated with a 5% relative increase in AF burden (adjusted estimate 1.05 [1.00-1.09], p = 0.039). Participants reaching prediabetes or diabetes accumulated longer AF durations and higher AF burden over time compared to participants with consistently normal HbA1c. CONCLUSION: Higher HbA1c levels were associated with higher AF burden and lower HbA1c levels were associated with lower AF burden and less accumulation of AF over time. TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT02036450.