Supplementary Material for: Association Between Parathyroid Hormone Concentration and Incident Atrial Fibrillation in Older Persons with Kidney Failure Initiating Dialysis

Background: Atrial fibrillation (AF) is common in persons with kidney failure on hemodialysis. In the general population, higher intact parathyroid hormone (iPTH) levels were found to be associated with presence of AF. Whether iPTH associates with AF in patients on hemodialysis is unknown.
Methods: Using merged USRDS-DaVita data (2006-2011) we selected persons aged 67+ years who initiated hemodialysis and survived 120 days. Eligible persons had continuous Medicare A+B coverage from 2 years prior to kidney failure and no diagnosis of AF. Sociodemographic, comorbidity, and clinical information was abstracted from Medicare forms, billing claims, and electronic health records. iPTH was categorized consistent with previous work: <150; 150-<300; 300-<600; and 600 pg/mL. Patients were followed for incident (ie, newly-diagnosed) AF as reflected in inpatient and outpatient claims. Unadjusted and multivariable Cox regression was used to estimate the associations of time-updated iPTH category (referent: 150-<300 pg/mL) with incident AF.
Results: Of 15,225 patients initiating hemodialysis, surviving 120 days, and without a prior diagnosis of AF, iPTH (in pg/mL) at baseline was <150 in 4479, 150-<300 in 5964, 300-<600 in 3479, and ≥600 in 1064 persons. During 21,845 patient-years 2857 patients had incident AF (rate, 13.1/100 person-years). After multivariable adjustment, patients with iPTH<150pg/mL had 13% (95% CI, 3-25%) higher relative AF incidence compared with the 150-<300 pg/mL group, but no association was found for those with iPTH 300-<600 (HR: 1.04; 95% CI, 0.95-1.14) or iPTH ≥600 pg/mL (HR: 0.90; 95% CI, 0.75-1.08).
Conclusion: Among persons with incident kidney failure on hemodialysis, compared with those whose iPTH was between 150 and <300 pg/mL, lower iPTH was independently associated with higher AF incidence; however, no association with AF was identified for higher iPTH levels.