As some of you may read recently, there was an article published by researchers that found that Apollo Lunar Astronauts show a higher cardiovascular disease mortality than their non-flight and lower earth orbit counterparts who did not travel beyond Earth’s magnetosphere. As science communicators it is our duty to accurately present information to the reader so they can better understand the research and the world around them. The information that the reader gets is the information that they construct their view of the world with. However, in the age of ‘click-bait’ and website marketing, the accuracy of certain articles can suffer.
The article by Delp, M.D et. al. states that the increased rate of deaths in Apollo astronauts may be caused by deep space radiation affecting their vascular endothelium (the tissue that lines blood vessels). The study compared a three groups; lower earth orbit astronauts, Apollo lunar astronauts, and non-flight astronauts. It also must be noted that the author stated that “The total time in space and the number of missions flown did not differ between lower Earth orbit and Apollo lunar astronauts.” However, there are a number of comparisons that could be misinterpreted by the reader.
The sample size of this research is very small. To be clear I’m not saying that they are intentionally misleading the reader, but rather highlighting that the reader needs to be weary and not come to any false conclusions.
The sample sizes for each three groups are as follows:
- Lower Earth Orbit astronaut subgroup was 35 people (5 females & 30 males)
- Non-flight astronaut subgroup was 35 people (3 females and 32 males)
- Apollo lunar astronaut subgroup was 7 people (7 males).
The author mentions that “[cardiovascular disease] in Apollo lunar astronauts was almost five times greater than that in the non-flight astronauts”. However the reader must be aware that the sample size for the Apollo astronauts is also 7 times less. This means that the sample size for lower Earth orbit astronauts is 7 times larger compared to the Apollo group!
Here lies a potential problem. When looking at these results the sample size of Apollo astronauts was significantly smaller! This means that any slight randomness in the smaller population will have a significant influence on that sample group. For example, if a teacher has teaches a class of five students and 3 of them get measles, meaning 60% of the class have measles. However, if three students in a class of 35 have measles then only 9% of the students have measles. This example, although very basic, helps to illustrate a potential problem with small sample sizes.
The study goes on to write that “Despite virtually identical estimates for galactic cosmic ray exposure, the mortality rate of LEO astronauts for CVD is significantly lower than in Apollo lunar astronauts.” This within itself could be misinterpreted by the reader or journalist. Yes, it is a correct statement, but it must be read with caution and this is even highlighted by the author
“the sample size for cause-specific deaths among lunar astronauts is small. Therefore, caution must be used in drawing definitive conclusions regarding specific health risks.”
However, this didn’t stop many websites posting what I consider misleading titles.
Take caution when just reading the headlines of articles, and much like a book- don’t judge an article by its title. What the title says may be twisted in a way to entice the reader to either read on, or it may lead them to false conclusions. With the amount of junk science permeating through the the ether it is more vital than ever that we have the correct information and tools to adequately interpret and also debunk it.