The Impact of Respiratory Function on Functionality and Mortality in ALS Patients

TL;DR

This study shows that respiratory function is closely linked to survival and quality of life in ALS patients, with specific measures like PEF and SNIP being strong predictors of mortality.

Contribution

The study identifies specific respiratory parameters that strongly correlate with mortality and functionality in ALS patients.

Findings

Respiratory variables like FVC%, SNIP, and MIP showed significant inverse correlations with mortality in ALS patients.

A one-unit reduction in PEF% predicted increased the risk of death by an average of 300%.

Respiratory measures correlated positively with ALSFRS-R scores, indicating their importance in assessing functionality.

Abstract

Objective: To investigate the relationship between respiratory function, functionality, and mortality in amyotrophic lateral sclerosis (ALS) patients and to determine which respiratory parameters show the strongest correlation with functionality and mortality. Methods: The study was conducted in Rio Grande do Norte, Northeast Brazil, between January 2018 and December 2023. This was a retrospective cohort, following individuals with ALS who were evaluated at the University Laboratory. Results: A total of 74 ALS patients were included in the analysis, with a mean age of 55.7 ± 13.5 years. Most were male (66.2%) and predominantly presented with spinal-onset ALS (51.3%). Respiratory variables (except peak expiratory flow (PEF)) showed a weak but significant inverse correlation with mortality (FVC% predicted (rpb = −0.260; p < 0.001), SNIP (rpb = −0.235; p = 0.001), MEP (rpb = −0.207; p = 0.007), MIP (rpb = −0.198; p = 0.009), and PEF% predicted (rpb = −0.156; p = 0.013)). When analyzing their correlation with ALSFRS-R, all variables showed a significant positive correlation (ranging from weak to moderate) with functionality. A reduction of one unit in the respiratory variables PEF% of predicted, maximal inspiratory pressure (MIP), and sniff nasal inspiratory pressure (SNIP) increased the risk of death by an average of 300% (OR = 2.99; 95% CI: 2.05–4.35), 2% (OR = 1.02; 95% CI: 1.01–1.03), and 1% (OR = 1.01; 95% CI: 1.00–1.02), respectively. Conclusions: Our findings suggest that direct measurements of respiratory function and muscle strength, particularly PEF and SNIP, may serve as more useful markers to guide early interventions such as non-invasive ventilation, thereby improving quality of life and potentially prolonging survival.

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