Baseline characteristics of the study population.

Abbreviations: No. Number of participants.
a Three levels of comorbidity was created based on the modified Charlson comorbidity index score (m-CCI) at the date of first treatment with renal replacement therapy “Low” (CCI = 0), “Medium” CCI 1–2, and “High” CCI > 2. See text for details.
b Index date: Date of first treatment (hemodialysis) for end-stage renal disease and date of sampling for population controls.
c For each patient on chronic hemodialysis, 19 persons from the background population were sampled matched on age, gender, and municipality.
Baseline characteristics of the study population.