Prognostic significance of body weight variation after diagnosis in ALS: a single-centre prospective cohort study

Background: Body weight reduction after disease onset is an independent predictor of survival in amyotrophic lateral sclerosis (ALS), but significance of weight variation after diagnosis remains to be established.

Objective: To investigate weight variation after diagnosis and its prognostic significance in patients with ALS as a prospective cohort study.

Methods: Seventy-nine patients with ALS were enrolled in this study. At the time of diagnosis and about 1 year later, we evaluated the following parameters: age, sex, onset age, onset region, body mass index (BMI) and premorbid BMI, forced vital capacity and the revised ALS functional rating scale. Annual BMI decline rates (∆BMI) from onset to diagnosis and from diagnosis to about 1 year later were calculated. Patients were followed to the endpoints (death or tracheostomy), and the relationships between ∆BMIs and survival were investigated.

Results: Patients with post-diagnostic ∆BMI ≥ 2.0 kg/m²/year showed shorter survival length than those with < 2.0 kg/m²/year (log-rank test, p < 0.0001), and multivariate analysis using the Cox model revealed post-diagnostic ∆BMI as an independent prognostic factor. No correlation was identified between pre- and post-diagnostic ∆BMIs. Female patients with post-diagnostic ∆BMI < pre-diagnostic ∆BMI showed longer survival than those with the opposite ∆BMI trend (log-rank test, p = 0.0147). Female patients with post-diagnostic weight increase showed longer survival than those with weight decrease (log-rank test, p = 0.0228).

Conclusion: Body weight changes after diagnosis strongly predicts survival in ALS, and weight gain after diagnosis may improve survival prognosis, particularly in female ALS patients.