Kidney function, uric acid, and risk of atrial fibrillation: experience from the AMORIS cohort.

Background: Uric acid closely relates to both kidney disease and atrial fibrillation (AF), yet the extent to which it influences the kidney-AF association remains uncertain. We examined the relationship between kidney function and risk of AF, accounting for uric acid levels.

Methods: A total of 308,509 individuals in the Swedish Apolipoprotein-Related Mortality Risk (AMORIS) cohort were included and their serum creatinine and uric acid were measured during 1985-1996. Ten-year incident AF was identified via linkage with the national registers. Glomerular filtration rate (eGFR) (ml/min/1.73 m) was calculated with the 2009 Chronic Kidney Disease Epidemiology Collaboration equation. Hyperuricemia was defined as > 420 µmol/L for men and > 360 µmol/L for women.

Results: Over a mean follow-up of 9.4 years, 10,007 (3.2%) incident AF cases occurred. After adjusting for age, sex, cardiovascular diseases, total cholesterol, triglycerides, and glucose, individuals with low eGFR (< 30 and 30-59 ml/min/1.73 m ) had a higher risk of AF compared to those with normal eGFR (60-89) (hazard ratio (HR) = 1.72, 95% confidence interval (CI):1.29-2.30; HR = 1.10, 95% CI: 1.03-1.18, respectively). After further adjusting for uric acid levels, the association disappeared (HR = 0.97, 95% CI: 0.72-1.30; HR = 0.93, 95% CI: 0.86-1.00, respectively). When stratifying by hyperuricemia yes/no, eGFR < 30 ml/min/1.73 m was associated with higher AF risk in a small group of individuals without hyperuricemia (HR = 2.58, 95% CI: 1.64-4.07).

Conclusion: Uric acid largely accounted for the relationship between eGFR and AF in this study. However, in individuals without hyperuricemia, eGFR in the lowest range (< 30 ml/min/1.73 m) was still associated with increased risk of AF.