Etiology-specific variation in survival following non-traumatic spinal cord injury: a causal inference approach using data from a population-based cohort

Anne Buzzell,Martin W G Brinkhof,Inge Eriks-Hoogland,Martin Schubert,Xavier Jordan,Marcel Zwahlen,Jonviea D Chamberlain

doi:10.1038/s41393-020-00554-9

Abstract

Study designObservational, population-based cohort study.ObjectivesTo evaluate the origin and contribution to excess of survival differences following non-traumatic spinal cord injury (NTSCI) using etiology as proxy for variation in underlying health condition.SettingSpecialized rehabilitation centers in Switzerland.MethodsMedical record data collected by the Swiss Spinal Cord Injury cohort (SwiSCI) study were linked with mortality information from the Swiss National Cohort. Considering contemporary theory and empirical evidence, a directed acyclic graph (DAG) was developed to formally evaluate causal differences among NTSCI etiologies, relative to traumatic SCI (TSCI). Statistical inference was contingent on hazard ratios (HRs) and marginal survival differences, derived using flexible parametric modeling.Results3643 individuals (NTSCI = 1357; TSCI = 2286) diagnosed with SCI between 1990 and 2011 were included, contributing a cumulative 41,344 person-years and 1323 deaths. Test statistics confirmed DAG-dataset consistency. As compared to TSCI, mortality was elevated in all NTSCI etiological groups; malignant etiologies had the highest HRs (10; 95% CI, 8.0 to 14) followed by infection (2.6; 1.8 to 3.6) and vascular (2.5; 2.0 to 3.2) etiology groups. At the attained age of 55, the estimated reduction in survival among non-malignant etiologies was 9.4% (5.8 to 13) at 5 years and 17% (11 to 23) at 20 years.ConclusionsCausal differences in survival among NTSCI etiological groups are likely a result of chronic variation in health conditions. This study supports the development of long-term interdisciplinary management and policy for individuals with NTSCI, specific to etiology.

Highlights

Supplementary information The online version of this article contains supplementary material, which is available to authorized users.Lucerne, Lucerne, Switzerland 3 University of Bordeaux, Inserm, Bordeaux Population HealthResearch Center, Team VINTAGE, UMR1219 Bordeaux, FranceNon-traumatic spinal cord injuries (NTSCI) are commonly associated with elevated mortality and reduced life expectancy [1,2,3,4]
For non-traumatic spinal cord injury (NTSCI), etiology-specific variation in chronic health conditions likely contribute to elevated mortality risk, mainly through acquired NTSCI etiologies; these include vascular disorders, neoplasms, and degenerative disc disorders, and infection
In order to define the scope for improving survival outcomes in NTSCI by adopting etiology-specific clinical management and health policy, population-based studies are needed that separate the mortality that is attributable to NTSCI etiology from lesion-related or demographicattributable mortality

Summary

Introduction

Non-traumatic spinal cord injuries (NTSCI) are commonly associated with elevated mortality and reduced life expectancy [1,2,3,4]. In order to define the scope for improving survival outcomes in NTSCI by adopting etiology-specific clinical management and health policy, population-based studies are needed that separate the mortality that is attributable to NTSCI etiology from lesion-related or demographicattributable mortality. Such studies are timely in face of the growth in incidence and prevalence of NTSCI [2, 7]. Using the causal estimates for mortality differentials, we estimated the disparity in survival that was directly attributable to etiology-specific differences

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