Activin A level is associated with physical function in critically ill patients.

Background: Activin A is a potent negative regulator of muscle mass elevated in critical illness. It is unclear whether muscle strength and physical function in critically ill humans are associated with elevated activin A levels.

Objectives: The objective of this study was to investigate the relationship between serum activin A levels, muscle strength, and physical function at discharge from the intensive care unit (ICU) and hospital.

Methods: Thirty-six participants were recruited from two tertiary ICUs in Melbourne, Australia. Participants were included if they were mechanically ventilated for >48 h and expected to have a total ICU stay of >5 days. The primary outcome measure was the Six-Minute Walk Test distance at hospital discharge. Secondary outcome measures included handgrip strength, Medical Research Council Sum Score, Physical Function ICU Test Scored, Six-Minute Walk Test, and Timed Up and Go Test assessed throughout the hospital admission. Total serum activin A levels were measured daily in the ICU.

Results: High peak activin A was associated with worse Six-Minute Walk Test distance at hospital discharge (linear regression coefficient, 95% confidence interval, p-value: -91.3, -154.2 to -28.4, p = 0.007, respectively). Peak activin A concentration was not associated with the secondary outcome measures.

Conclusions: Higher peak activin A may be associated with the functional decline of critically ill patients. Further research is indicated to examine its potential as a therapeutic target and a prospective predictor for muscle wasting in critical illness.

Study Registration: ACTRN12615000047594.