Table S1. Comparison between Patients With and Without Clinic Visits at ALS Association Registered Clinics.

Table S2. Median Time from Symptom Onset to Diagnosis and Diagnosis to Death for Demographic and Clinical variables.

Table S3. Relative Effects of Predictors with Time from Diagnosis to Death of All Participants.

Figure S1. Kaplan–Meier plots for Time from Diagnosis to Death. X-axis represents time from diagnosis to death in months, and y-axis represents cumulative survival. (A) Region of onset – 0: unknown onset, 1: bulbar onset, 2: limb onset, 3: respiratory onset. (B) Age at diagnosis, solid line: 65 years of age or younger, dotted line: older than 65. (C) Gastrostomy in use, solid line: no, dotted line: yes. (D) Non-invasive ventilator (NIV) in use, solid line: no, dotted line: yes. (E) Tracheostomy – solid line: no, dotted line: yes.

Figure S2. Survival Curves of Patients Diagnosed in Each Calendar Year. X-axis represents time from diagnosis to death in months, and y-axis represents cumulative survival. Participants who were diagnosed closer to the end of study period had shorter survival, as survivors were excluded from the dataset, demonstrating shorter survival due to lack of censored (alive) cases. Participants diagnosed before 2010 were excluded from the graph.

Figure S3. Longer Survivors with NIV use Did Not Have Symptom Onset Available. Histogram of time from diagnosis to death. Left column represents participants without time of symptom onset available, right column represents participants with symptom onset available; top raw denotes patients without NIV use, bottom raw illustrates patients with NIV use. Long survivors who lived for 60 months to 100 months are circled, showing that long survivors with NIV use tended not to have time of symptom onset available.

Figure S4. Survival Curves with Sample Augmentation of Censored Cases. (A) X-axis represents time from symptom onset to death in months, and y-axis represents cumulative survival. (B) X-axis represents time from diagnosis to death in months, and y-axis represents cumulative survival. Black dots represent simulated censored cases.