Association Between Onset of Type 2 Diabetes and Risk of Atrial Fibrillation in New Zealanders With Impaired Glucose Tolerance Over 25 Years.

Background The association between the onset of type 2 diabetes (T2D) and atrial fibrillation (AF) risk in individuals with impaired glucose tolerance (IGT) remains unclear. This study aimed to investigate the relationship between the incident onset of T2D and 5- and 10-year (after the landmark period) risks of AF in people with IGT identified in South and West Auckland primary care settings between 1994 and 2019. Methods and Results We compared AF risk in patients with IGT with and without newly diagnosed T2D within a 1- to 5-year exposure window. Tapered matching and landmark analysis (to address immortal bias) were used to control for confounding variables. The cohorts incorporated 785 patients who had T2D newly diagnosed within 5 years from enrollment (landmark date) and 15 079 patients without a T2D diagnosis. Patients progressing to T2D exhibited significantly higher 5-year (after the landmark period) AF risk (hazard ratio [HR], 1.34 [95% CI, 1.10-1.63]) and 10-year (after the landmark period) AF risk (HR, 1.28 [95% CI, 1.02-1.62]) compared with those without incident T2D. The association was more pronounced among men, older patients, socioeconomically deprived individuals, current smokers, those with higher metabolic measures, and lower renal function. New Zealand European ethnicity was associated with a lower 5- and 10-year risk of AF. Conclusions This study found a mediating effect of T2D on the risk of AF in a population with IGT in New Zealand. The development of risk scores and future replication studies can help identify and guide management of individuals with IGT at the highest risk of AF following incident T2D.