Afib and T1D: Linked by Cause or Correlation?

The relationship between atrial fibrillation (AF) and diabetes mellitus (DM) is a complicated one and the jury is still out on whether the link between the two diseases is cause or correlation.¹ Multiple epidemiologic studies have shown an association between DM and AF. Theories suggest that this relationship may be causal (ie, DM leads to increased risk of AF), possibly as a result of aberrations in autonomic nervous tone or of pathologic changes in atrial tissue from hyperglycemia. Alternatively, DM and AF share multiple risk factors, including obesity, hypertension, and sleep apnea and so the relationship may instead be associative. DM certainly increases thromboembolic risk and is therefore included in the CHA₂DS₂-Vasc risk score.

In a recent study published in Lancet Diabetes Endocrinology,² a Swedish cohort study investigated the relationship between type 1 DM (T1DM) and AF (which has not apparently been previously studied). Using national population registries, 36,258 patients with T1DM were matched with 179,980 propensity matched controls and followed for ~10 years. The incidence of AF was higher in participants with T1DM than it was in the general population.

The study reported a statistically significant p-value for interaction (p=0.019) with a HR for incident AF of 1.13 (1.01-1.25) in men and 1.50 (1.30-1.72) in women with risk of AF increasing along with parameters that reflected worse glycemic control (glucose control, renal complications). Interestingly, in individuals who had no clear evidence of end-organ damage (ie, did not meet threshold for microalbuminuria), there was no increase in AF risk with relatively liberal A1c thresholds (men with A1c <9.7% or women with A1c <8.8%). Above these thresholds, women carried an increased risk in the setting of microalbuminuria but men had no increased risk if eGFR >60 ml/min. Risk for men only increased in the setting of advanced renal dysfunction.

This study is apparently the first of its kind to report an association between T1DM and AF and between glycemic control and AF. It also highlights an interesting gender difference, whereby, after adjusting for renal complications, women had an increased risk of AF based on A1c but men did not. This was true despite the fact that the incidence of AF was higher in men compared with women. Hyperglycemia was also a stronger risk factor for AF for women compared to men. Finally, by raising awareness of the increased risk for AF in patients with DM, the authors make a case for potentially screening patients with T1DM more carefully and also targeting strict glycemic control to minimize risk of incident AF, especially in women.
 

References:

1. Sun Y, Hu D. The link between diabetes and atrial fibrillation: cause or correlation?  J Cardiovasc Dis Res. 2010;1:10–11.

2. Dahlqvist S, Rosengren A, Gudbjörnsdottir S, et al. Risk of atrial fibrillation in people with type 1 diabetes compared with matched controls from the general population: a prospective case-control study. Lancet Diabetes Endocrinol 2017; 5: 799–807.