Impact of trajectories of abdominal aortic calcification over 2 years on subsequent mortality: a 10-year longitudinal study

Background. Although both the presence and progression over time of vascular calcification have been shown to independently predict cardiovascular disease and mortality in chronic dialysis patients, the impact of the pattern of accumulation of abdominal aortic calcification on mortality has not yet been investigated. Methods. We conducted a longitudinal study at a dialysis hospital in Hokkaido, Japan from 2005 to 2014. An abdominal calcification index (ACI) was generated for 396 patients from their annual abdominal computed tomography (CT) scans. The trajectories of ACIs during the first 2 years were classified using group-based trajectory modeling into four groups; stable (29.0%), slow increase (29.2%), rapid nonlinear increase (24.4%) and advanced with slow increase (17.4%). Incidence rates by group of all-cause mortality during the follow-up period (mean of 4.5 years) were investigated using the Cox proportional hazard model. Results. Compared with the stable trajectory, both the rapid nonlinear increase and the advanced with slow increase trajectories were associated with an increased risk of death [adjusted hazard ratios (HR) 1.91; 95% confidence interval (CI) 1.02-3.58 and adjusted HR 2.79; 95% CI: 1.44-5.11, respectively]. Sensitivity analyses indicated that ACI trajectories were associated with subsequent mortality, while ACI at individual time points was not. Conclusions. Chronic hemodialysis patients with a trajectory of longitudinal high or rapid accumulation of vascular calcification over time were at a higher risk of death. Individual trajectories of vascular calcification may be suggested to allow for more accurate mortality risk calculations than one-time assessment.