Respiratory function, survival, and NIV prevalence over time in ALS - a PRECISION ALS study

Introduction: Respiratory function typically deteriorates as ALS progresses and is associated with shorter survival. This study aims to describe respiratory function and the prevalence of noninvasive ventilation (NIV) along the disease trajectory using prospective data from the PRECISION ALS project. Methods: We included 3449 ALS patients from six European population-based cohorts. All had comparable assessments of vital capacity, percent predicted (VC%) (58.1% had multiple assessments) and 56% had assessments of the revised ALS Functional Rating Scale (ALSFRS-R). The data were analyzed in relation to survival, NIV, and genetic status (C9orf72, SOD1, FUS, and TARDBP). Results: In those with a survival time of 1-4 years from diagnosis, the median VC% declined from 91 to 97% at the first assessment to 47-50% at the last assessment 6 months before death. In those with longitudinal assessments, the median VC% declined an average of 24 percentage points per year. Over time, there was an increase in respiratory symptoms relative to general functional impairment, as measured by the ALSFRS-R, and VC% was strongly associated with shorter survival. The confirmed prevalence of NIV was approximately 3%, 15%, and 25% in patients with a VC% of >80, 50-80, and <50, respectively. Conclusion: There was a trend of worsening respiratory function over time and an increase in respiratory symptoms relative to general functional impairment. Survival was strongly associated with respiratory function. In those with impaired respiratory function, there was significant variation in the introduction of NIV.