Okay Houston, we’ve got a problem. We need more power. Case in point: a recently published study Apollo Lunar Astronauts Show Higher Cardiovascular Disease Mortality by Michael Delp et al. was picked up by news outlets with headlines such as:
- Study finds cosmic rays increased heart risks among Apollo astronauts (Reuters)
- Deep space radiation caused heart problems for Apollo astronauts (NBC News)
- Apollo deep space astronauts five times more likely to die from heart disease (The Guardian)
- Space radiation took a toll on Apollo astronauts, study says (Fox News)
- Apollo astronauts much more likely to die from heart disease (Science)
- … etc., etc., …
The headlines were based on a sentence in the paper stating that “the CVD mortality rate among Apollo lunar astronauts (43%) was 4–5 times higher than in non-flight and LEO [low earth orbit] astronauts.”
A reading of the paper reveals that the “5 times more likely to die” risk calculation comes from . The number 9% is the rate of cardiovascular disease observed in 35 non-flight astronauts whereas the number 43% is rate of cardiovascular disease in Apollo lunar astronauts (3 out of 7). In other words, the grandiose claims of the paper are based on three Apollo astronauts dying of cardiovascular disease rather than an expected single astronaut.
The authors themselves must have realized how unfounded their claims were, because the paper evidently flirts with fraud. They used a p-value cutoff of 0.1 to declare the lunar astronaut result “significant”. This is in contrast to the standard cutoff 0.05 which they use for the remainder of the results in the paper, and they justified the strange exception by suggesting that others “considered [Fisher’s exact test] extremely conservative.” In addition, Ed Mitchell who died at the age of 85 on February 4th 2016 three months before the paper was submitted was excluded from the analysis. His inclusion would have increased the dataset size by 14%! Then there is the fact that they failed to mention the three astronauts who visited the moon twice and are still alive. Or that the lunar astronauts died ten years older on average. Perhaps worst of all, the authors imply that they have experimental data on a mechanism for their statistical (non)result by describing a follow-up experiment examining vascular responses of resistance arteries in irradiated mice. The problem is, the dose given to the mice was 87 times what the astronauts received! None of this is complicated stuff… and one wonders how only one of the reporters writing about the study picked up on any of this (Sarah Kaplan from the Washington post headlined the story with Studying heart disease in astronauts yields clues but not conclusive evidence and concluded correctly “that’s just three of seven people, which doesn’t give you a whole lot of statistical power”.)
One would hope that this kind of paper would be retracted by the journal but my previous attempts to get journals to do the right thing, even when the research was clearly flawed, have been futile. Then there is the funding. Learning nothing doesn’t come for free and the authors’ “work” was supported by grants from the National Space and Biomedical Research Institute under the NASA Cooperative Agreement. Clearly PI Michael Delp (who is also first author, corresponding author and dean of the College of Human Sciences at Florida State University) would like even more funding, proclaiming in interviews that he wanted to take “a deeper look into the medical history of the Apollo astronauts”, “study future questions” and that he was “working with NASA to conduct additional studies”. My experience in genomics has been that funding agencies typically turn a blind eye to flawed research leaving the task of evaluating the science to “peer reviewers”. I’ve seen many cases where individuals who published complete malarkey and hogwash continue to receive funding. But it seems NASA cares about the research it funds and may not be on the same page as Delp et al. In a statement published on July 28th, NASA wrote that:
The National Space Biomedical Research Institute, a non-governmental organization with funding from NASA’s Human Research Program, supported a recent study published in Scientific Reports that looked at the rate of cardiovascular disease among Apollo astronauts.
With the current limited astronaut data referenced in the study it is not possible to determine whether cosmic ray radiation affected the Apollo astronauts.
This is not the first time NASA has published statements distancing itself from studies it has supported (either directly or indirectly). Following reports that a NASA-funded study found that industrial civilization was headed for irreversible collapse, NASA published a statement making clear it did not support the results of the study.
Thank you NASA! You have set a great example in taking ownership of the published work your funding enabled. Hopefully others (NIH!!) will follow suit in publicly disavowing poorly designed underpowered studies that make grandiose claims.
Disclosure: I collaborate with NASA scientists, contribute to projects partially funded by NASA, and apply for NASA funding.