REVEALS-a longitudinal cohort study of multifaceted respiratory assessment in ALS

To systematically assess decline in respiratory measures in amyotrophic lateral sclerosis (ALS) and to examine the impact of sex, disease onset type and baseline morbidity on progression.

The REVEALS study (Registry of Endpoints and Validated Experiences in ALS) was conducted between April 2018 and February 2021 in six European ALS centers. Slow and forced vital capacity (S/FVC), sniff nasal inspiratory pressure (SNIP), peak cough flow, amyotrophic lateral sclerosis functional rating scale-revised (ALSFRS-R), and respiratory morbidity were collected. Data were analyzed using a Bayesian multiple outcomes random effects model.

Two hundred and eighty participants had a median of three assessments (IQR 2.0, 5.0) over a median of 8 months (IQR 2.3, 14.1). There were 974 data collection timepoints. Differences in respiratory measures and rates of decline between disease-onset and sex subgroups were identified. Females had lower scores in all respiratory measures and females with bulbar onset ALS had faster decline compared with other sub-groups. These differences were not detected by the ALSFRS-r respiratory subscale. Dyspnea, orthopnea, and a higher King's stage at baseline were associated with lower respiratory scores throughout follow-up, while having a regular productive cough at baseline was associated with lower peak cough flow scores.

Respiratory function declines more quickly in females with ALS compared with males when measured by FVC, SVC, SNIP, or PCF, but not the ALSFRS-R respiratory sub-score. Higher baseline King's staging and the presence of clinical respiratory symptoms at baseline were associated with worse respiratory function. The ALSFRS-R respiratory sub-score is poorly correlated with objective respiratory measurements.