Dialysis Modality and Rates of Incident Atrial Fibrillation in Older Adults

Atrial fibrillation (AF), the most common sustained arrhythmia in the general population, is particularly common among patients with end-stage renal disease (ESRD). The prevalence of AF is as high as 10% among patients in the United States on hemodialysis. There is a steep increase in the percentage with age, reaching as high as 25% of patients ≥85 years of age. Among older patients, the cumulative incidence of newly diagnosed AF during the first year of dialysis therapy is nearly 15%.

AF is associated with poor health outcomes that include higher mortality rates, excess rates of ischemic stroke, systemic thromboembolism, myocardial infarction, heart failure, and kidney disease. Patients with ESRD and AF also incur increased healthcare costs.

There are several risk factors for the development of AF including sociodemographic characteristics (older age, female sex, white race, and non-Hispanic ethnicity), and chronic conditions such as heart failure, diabetes, and hypertension; these factors increase the risk of AF in the population of patients with kidney failure receiving maintenance dialysis.

According to Jingbo Niu, MD, DSc, and colleagues, there are few data available on whether the modality used for renal replacement therapy poses a risk factor for AF among dialysis patients. The researchers conducted a retrospective cohort study designed to challenge the null hypothesis of no difference in incidence of AF between incident patients with ESRD in a large ESRD registry using peritoneal dialysis versus hemodialysis. Results of the study were reported in the American Journal of Kidney Diseases [2019;73(3):324-331].

Utilizing the US Renal Data System database, the researchers identified adults 67 to 99 years of age with incident ESRD who initiated long-term dialysis therapy between January 1, 1996, and December 31, 2011, in the 50 states and the District of Columbia. There were 271,722 patients eligible for inclusion. Of those, 6.4% (n=17,487) initiated dialysis using peritoneal dialysis and 93.6% (n=254,235) initiated dialysis using hemodialysis.

Overall, median age of the cohort was 75 years, 51% were women, 73% were white, 23% were black, and 8% were Hispanic. Patients in the peritoneal dialysis cohort were younger, more likely to be male and white, had fewer comorbid conditions, and were less likely to be impaired in their ambulation or ability to transfer. Hemodialysis patients had fewer visits with nephrologists prior to initiation of dialysis therapy as well as lower serum albumin concentrations.

Overall follow-up was an average of 1.5 years, contributing 406,225 person-years. During follow-up, 69,705 participants had newly diagnosed AF. In the first months following the index date, individuals in the peritoneal dialysis group had lower unadjusted rates of AF; the differences narrowed over the remaining follow-up to 36 months. The unadjusted incidence rate of AF was lower among the peritoneal dialysis group compared with the hemodialysis group (152.0 vs 173.2/1000 person-years). The difference was confirmed by formal Cox regression models (multivariable-adjusted cause-specific hazard ratio [HR], 0.96; 95% confidence interval [CI], 0.93-0.99; subdistribution HR, 0.92 [95% CI, 0.89-0.95]).

However, because the proportionality assumption was violated, the researchers conducted analyses by separating follow-up time into two periods at 3 months (≤90 days vs >90 days), and including an interaction term between modality and time into the model. There was no residual violation of the proportionality assumption observed within either of the two periods.

A total of 21,709 patients developed incident AF during the first 3 months of dialysis therapy, and 22,241 patients without AF died. The unadjusted incidence rate of AF was 186.6 per 1000 person-years in the peritoneal group and 372.0 per 1000 person-years in the hemodialysis group. Estimates of association from the cause-specific model suggested that patients on peritoneal dialysis therapy had an adjusted 43% (95% CI, 38%-47%) lower incidence of AF compared with those on hemodialysis therapy.

From month 4 onward, 224,176 patients were followed for incident AF. During up to 33 additional months of follow-up, there were 47,996 incident events over 345,276 person-years. In the peritoneal dialysis group, the unadjusted rate of AF incidence was 145.2 per 1000 person-years; in the hemodialysis therapy group, the unadjusted rate was 138.6 per 1000 person-years.

After controlling for all demographic and recorded health-related characteristics and comorbid conditions, the multivariable-adjusted cause-specific HR for peritoneal dialysis versus hemodialysis was 1.14 (95% CI, 1.10-1.19). After accounting for the competing risk for death, the difference in the risk for incident AF between the two groups essentially disappeared (subdistribution HR, 1.05 [95% CI, 1.01-1.09]).

Study limitations included the observational design of the study; possible confounding due to unobserved differences between exposure groups; ascertaining incidence of AF from billing claims; and the possibility that the findings may not be generalizable to younger patients.

In conclusion, the researchers said, “We found that AF incidence differed between older patients initiating dialysis therapy using peritoneal dialysis versus hemodialysis in the United States, specifically that patients using hemodialysis had increased AF risk during the first 3 months. Thereafter, the adjusted incidence of AF was similar between patients receiving hemodialysis versus peritoneal dialysis. This study highlights the opportunity to further investigate the high rate of mortality, in particular as it related to arrhythmia, in patients with ESRD new to dialysis therapy.”

Takeaway Points

  1. Researchers conducted a retrospective cohort study to determine whether there is a difference in incidence of atrial fibrillation (AF) between patients with end-stage renal disease receiving hemodialysis and those receiving peritoneal dialysis.
  2. During the first 3 months of dialysis therapy, patients on peritoneal dialysis had an adjusted 39% lower incidence of AF compared with patients on hemodialysis.
  3. From day 91 onward, the incidence of AF was ~140 per 1000 person-years; there were no differences between the two modality groups.