Although returning crewmembers have higher incidence of disc herniation post-flight, it is unknown if this increased incidence is related or contributes to an increased risk of injury due to dynamic loads. The aims of this study are as follows:
Of the 51 observed HNP, 19 were cervical, 3 were thoracic, and 29 were lumbar. In addition, 46 of the 51 were observed after long-duration missions, and 40 of the 51 were observed after Space Shuttle missions. Other than a small effect of age at selection, there was little evidence that mission duration, type of landing vehicle, or other demographic variables contributed to the model fit. In general the HNP risk after missions drops off sharply. However, the actual form of the distributional functions depends on the number and timing of missions, even in the no-covariate model. In a hypothetical crewmember with multiple flights, despite a sharp drop in the individual hazards related to each space flight, there would be enough carryover from one flight to the next in this hypothetical case to produce a noticeable upward trend in HNP risk as the number of flights increases.
Attribution of HNPs to Space flight
One of the most important questions addressed by this study was to separate the effects of space flight from those of the general astronaut training and lifestyle. Using point estimates of the parameters to the 40 cases of HNP observed after at least one space mission, yielded values of P ranging from 0.037 to 0.970 depending on when the HNP was reported. As expected, this probability is highest for HNP’s reported shortly after the latest mission for each astronaut.
A total of 745 out of 789 astronaut-missions took place before crewmembers’ first diagnosed HNP. Of these, 58 (7.8%) were “long-duration” and 98 (13.2%) were capsule landings. No evidence of an effect of either flight duration or landing vehicle on HNP propensity after space flight was seen. There was no strong evidence that sex, height, weight, body mass index (BMI), or a history of high-performance jet aircraft piloting had an effect on HNP risk either. However, astronauts that were older at the time of selection appeared to have higher risk (P = 0.038). In addition, pre-Shuttle astronauts had generally lower risk of HNP (P = 0.012).
No datasets exist for this study. A final report was archived.
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