Meta-analysis of health research data from greater than three months International Space Station missions

Abstract

Despite extensive research, the understanding of human health changes that result from long-duration spaceflight remains limited, in part due to the wide range of study types and designs, lack of independent experiment replication and data dispersal in many articles. We have compiled a database from 37 health studies that reported data for 517 parameters from missions of longer than 3-month duration on the International Space Station. We found an abundance of physiological and biochemical parameters and limited psychological/behavioral in-flight data. When we compared in-flight to pre-flight data, 14 out of 40 studied measurement type categories changed significantly, whereas only 3 categories changed significantly post-flight. Collagen breakdown biomarkers in urine showed the greatest effect, a 2-fold increase in-flight, but no data in this category was reported post-flight. Eye movements related to the vestibular system function had the greatest in-flight effect that was sustained post-flight, with a decrease of 81% in-flight and a 32% decrease remained post-flight. Analysis of the in-flight compared to post-flight biochemical and physiological changes revealed overall low correlations (R2 = 0.03 & R2 = 0.23, respectively), as parameters tend to return to baseline post-flight. As we look to longer duration space missions, this review provides an opportunity to identify and highlight salient results that have been reported to date for long duration spaceflight, to enhance our understanding of space health and to develop effective countermeasures. We believe that the compiled data could be explored for medical interpretation of the observed changes, in-flight timeline of changes for natural history studies, correlation analysis for parameters across different body systems, and comparison of in-flight responses to ground-based studies.