Attrition from specialised rehabilitation associated with an elevated mortality risk: results from a vital status tracing study in Swiss spinal cord injured patients

INTRODUCTION: Study drop-out and attrition from treating clinics is common among persons with chronic health conditions. However, if attrition is associated with adverse health outcomes, it may bias or mislead inferences for health policy and resource allocation. METHODS: This retrospective cohort study uses data attained through the Swiss Spinal Cord Injury (SwiSCI) cohort study on persons with spinal cord injury (SCI). Vital status (VS) was ascertained either through clinic medical records (MRs) or through municipalities in a secondary tracing effort. Flexible parametric survival models were used to investigate risk factors for going lost to clinic (LTC) and the association of LTC with subsequent risk of mortality. RESULTS: 1924 individuals were included in the tracing study; for 1608 of these cases, contemporary VS was initially checked in the MRs. VS was ascertained for 704 cases of the 1608 cases initially checked in MRs; of the remaining cases (n=904), nearly 90% were identified in municipalities (n=804). LTC was associated with a nearly fourfold higher risk of mortality (HR=3.62; 95% CI 2.18 to 6.02) among persons with traumatic SCI. Extended driving time (ie, less than 30 min compared with 30 min and longer to reach the nearest specialised rehabilitation facility) was associated with an increased risk of mortality (HR=1.51, 95% CI 1.02 to 2.22) for individuals with non-traumatic SCI. CONCLUSION: The differential risk of LTC according to sociodemographic and SCI lesion characteristics underscores the importance of accounting for attrition in cohort studies on chronic disease populations requiring long-term care. In addition, given the associated risk of mortality, LTC is an issue of concern to clinicians and policy makers aiming to optimise the long-term survival of community-dwelling individuals with traumatic SCI. Future studies are necessary to verify whether it is possible to improve survival prospects of individuals LTC through more persistent outreach and targeted care.