Non-invasive ventilation (NIV) is a cornerstone of respiratory management in amyotrophic lateral sclerosis (ALS), extending survival and relieving symptoms of respiratory failure.1 2 However, ALS has highly heterogeneous patterns of onset and progression, and the optimal timing for NIV initiation remains debated.3 4 In this issue of Thorax, Tankéré et al5 used the French national health database (Système National Des Données De Santé; SNDS) to analyse health trajectories around NIV initiation in a large ALS cohort. Their study aimed to identify phenotypic subgroups and evaluate whether starting NIV earlier compared with later affects survival outcomes.

The authors identified over 3400 people with ALS who received NIV between 2015 and 2019. Using time-sequence clustering, they described four distinct care trajectories. Two clusters had a longer interval between ALS diagnosis and NIV start (defined as ‘late’ NIV initiation), and two had a shorter…