# Is NASA's Kelly twin study of people living in Space flawed?
**URL:** https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442
**Category:** Factual Questions
**Created:** [April 12, 2019, 4:34pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442 "2019-04-12T16:34:01Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@aceplace57](https://boards.straightdope.com/u/aceplace57)
#### Post date: [April 12, 2019, 4:34pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/1 "2019-04-12T16:34:01Z")
_Mods_ There should be a GQ answer based on The Scientific Method.
NASA’s Kelly twin study of people living in Space is very interesting. Appears to have invaluable information for medical research.
But, _both men_ have lived on the International Space Station. Doesn’t that effect the accuracy of the study?
> **[Astronaut Mark Kelly: Biography](https://www.space.com/33111-mark-kelly-astronaut-biography.html)**
>
> Mark Kelly is one-half of the only set of twins to fly into space.
> **[Scott Kelly Spent a Year in Orbit. His Body Is Not Quite the Same. (Published...](https://www.nytimes.com/2019/04/11/science/scott-mark-kelly-twins-space-nasa.html)**
>
> NASA scientists compared the astronaut to his earthbound twin, Mark. The results hint at what humans will have to endure on long journeys through space.
> [@](#):
>
> In the run-up to the mission’s announcement, Mr. Kelly asked officials if they had any plans to compare him to his twin. “We have these two guys who are genetically identical,” Mr. Kelly recalled telling them. “They’d make for an interesting experiment.”
>
> Officials had no such plans, but soon decided to take him up on the offer. Mark Kelly agreed, and the NASA Twins Study was born. (Mark Kelly, who retired from NASA in 2011 and is the husband of former Representative Gabrielle Giffords, is running for John McCain’s Senate seat in Arizona.)
>
> By comparing the brothers, NASA hoped to better understand the changes that Scott Kelly experienced during his mission.
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### Author:  [@aceplace57](https://boards.straightdope.com/u/aceplace57)
#### Post date: [April 12, 2019, 4:42pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/2 "2019-04-12T16:42:25Z")
As a second question, why does the NY Times call it the NASA Twins Study?
Twin is a plural noun already. 😉
_nit-pick_
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### Author:  [@Just\_Asking\_Questions](https://boards.straightdope.com/u/Just_Asking_Questions)
#### Post date: [April 12, 2019, 4:47pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/3 "2019-04-12T16:47:49Z")
Mark never lived on the ISS. He just visited. He has only 54 days in space total, compared to 520 for Scott.
yes it would have been better to have a control. As long as this is only one data point, and they don’t draw conclusions from it, there’s nothing wrong with the study.
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### Author:  [@Charlie\_Tan](https://boards.straightdope.com/u/Charlie_Tan)
#### Post date: [April 12, 2019, 5:30pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/4 "2019-04-12T17:30:20Z")
Mark is one of the brothers. He’s a twin.
Scott is his brother, he’s also a twin.
Together they are two (2) …
a. twin
b. twins
Place your bets ladies and gentlemen! Which will Acey pick?
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### Author:  [@markn\_1](https://boards.straightdope.com/u/markn_1)
#### Post date: [April 12, 2019, 5:37pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/5 "2019-04-12T17:37:18Z")
> [@aceplace57](#):
>
> Twin is a plural noun already. 😉
Is this some kind of joke that I’m not getting? I just checked 5 dictionaries and none of them show “twin” as a plural noun. Where (if you’re not joking) do you get the idea that it is?
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### Author:  [@Jasmine](https://boards.straightdope.com/u/Jasmine)
#### Post date: [April 12, 2019, 5:40pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/6 "2019-04-12T17:40:17Z")
Well, repetition is an important part of the scientific method. Repeating an experiment numerous times and compiling results from all of those experiments goes a long way in ruling out chance as a variable. In this particular instance, we have one set of twins and that’s it. Perhaps some of those changes/variances can be attributed to him as an individual. There’s no way of knowing for sure unless we repeat the experiments with, for example, 100 sets of twins.
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### Author:  [@aceplace57](https://boards.straightdope.com/u/aceplace57)
#### Post date: [April 12, 2019, 5:44pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/7 "2019-04-12T17:44:01Z")
> [@markn\_1](#):
>
> Is this some kind of joke that I’m not getting? I just checked 5 dictionaries and none of them show “twin” as a plural noun. Where (if you’re not joking) do you get the idea that it is?
Twin represents two people by definition.
Triplet represents three people by definition.
Quintuplet represents five people by definition.
I have always used the collective noun as singular in formal writing my entire life. I’ve never had any professor comment in grading my academic writing.
I don’t want to derail the thread by a harmless nitpick.
You could argue endlessly why people say a pair of pants. It’s not worth the time or energy.
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### Author:  [@pulykamell](https://boards.straightdope.com/u/pulykamell)
#### Post date: [April 12, 2019, 5:47pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/8 "2019-04-12T17:47:54Z")
> [@aceplace57](#):
>
> Twin represents two people by definition.
> Triplet represents three people by definition.
> Quintuplet represents five people by definition.
>
> I have always used the collective noun as singular in formal writing my entire life.
>
> I’ve never had any professor comment in any of my academic writing.
???
“A twin” represents one person in a group of twins.
“A triplet” represents one person in a groups of triplets.
Mothers don’t give birth to “twin” and “triplet.” They give birth to “twins” and “triplets” (note the plural marker.) My father is a twin. He and his brother are twins. My grandmother gave birth to twins. Only the individual is a “twin.” The set is “twins.”
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### Author:  [@BubbaDog](https://boards.straightdope.com/u/BubbaDog)
#### Post date: [April 12, 2019, 5:50pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/9 "2019-04-12T17:50:48Z")
I see **aceplace57** ’s point.
A study of dog **s** would most likely be called a “Dog Study”
So, I can see that a study of twin **s** would most likely be called a “Twin Study”
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### Author:  [@pulykamell](https://boards.straightdope.com/u/pulykamell)
#### Post date: [April 12, 2019, 5:53pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/10 "2019-04-12T17:53:58Z")
I mean, [here is the Merriam-Webster dictionary definition of the word](https://www.merriam-webster.com/dictionary/twin):
> [@](#):
>
> Definition of twin (Entry 1 of 3)
> 1a : either of two offspring produced in the same pregnancy
> b Twins plural : GEMINI
> 2 : one of two persons or things closely related to or resembling each other.
Note that they refer to ONE person in the set. If your professors didn’t comment, either you are misremembering how you wrote your sentence or your professors just didn’t care for some reason. “Twin” is not a collective noun.
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### Author:  [@pulykamell](https://boards.straightdope.com/u/pulykamell)
#### Post date: [April 12, 2019, 5:55pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/11 "2019-04-12T17:55:12Z")
> [@BubbaDog](#):
>
> I see **aceplace57** ’s point.
>
> A study of dog **s** would most likely be called a “Dog Study”
>
> So, I can see that a study of twin **s** would most likely be called a “Twin Study”
That’s a separate issue from “Twin is a plural noun already,” which it emphatically is not.
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### Author:  [@aceplace57](https://boards.straightdope.com/u/aceplace57)
#### Post date: [April 12, 2019, 5:56pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/12 "2019-04-12T17:56:16Z")
Ok, I must of been absent that day in English. 😉
I’ve never had any teacher or professor challenge my use of the word. I never had any reason to consult Webster.
I humbly stand corrected.
BubbaDog is correct, dog study, twin study does ring more pleasing in my ear. I was mistaken why it sounds better. But Twins Study just jarred me when I read it. It sounds like 4 people, two sets of twins.
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### Author:  [@BubbaDog](https://boards.straightdope.com/u/BubbaDog)
#### Post date: [April 12, 2019, 5:57pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/13 "2019-04-12T17:57:33Z")
> [@pulykamell](#):
>
> That’s a separate issue from “Twin is a plural noun already,” which it emphatically is not.
So, are you’re saying my statement is wrong or are you just arguing the term?
edit: my reply sounds snarky (unintentional) I actually want to know if my logic is wrong
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### Author:  [@bonzer](https://boards.straightdope.com/u/bonzer)
#### Post date: [April 12, 2019, 5:57pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/14 "2019-04-12T17:57:40Z")
Speaking as an identical twin who has a longstanding scepticism about “twin studies”, the one thing that made me go “oh, that’s a bit different” about this one is that they not only had the twin brother as the control, they had the “astronaut twin brother” as the control. For I might guess that being acceptable as a NASA astronaut is a bigger overall commonality factor than being identical twins.
The fact that both of them have not only qualified as astronauts, but have flown (NASA’s choice about who they put into space being currently presumably - as it was broadly historically - _fairly_ hardheaded) is thus a plus for them as initially comparable.
[And to deal with the hijack, I have no problem with “twin studies” as the generic term. It’s the historic usage and inoffensive, at least from my POV.]
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### Author:  [@Jasmine](https://boards.straightdope.com/u/Jasmine)
#### Post date: [April 12, 2019, 5:59pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/15 "2019-04-12T17:59:53Z")
> [@pulykamell](#):
>
> ???
>
> “A twin” represents one person in a group of twins.
>
> “A triplet” represents one person in a groups of triplets.
>
> Mothers don’t give birth to “twin” and “triplet.” They give birth to “twins” and “triplets” (note the plural marker.) My father is a twin. He and his brother are twins. My grandmother gave birth to twins. Only the individual is a “twin.” The set is “twins.”
Exactly. I’ve never heard it any other way. The singular form is often used as an adjective also. “Fred has a twin brother in fifth grade.” “His private plane has twin engines.”
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### Author:  [@echoreply](https://boards.straightdope.com/u/echoreply)
#### Post date: [April 12, 2019, 6:02pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/16 "2019-04-12T18:02:34Z")
Careful about the ideal being the enemy of the attainable. Yes, obviously, if we could randomly assign the members of 500 twin pairs as either the space-living or ground-living twin, that would answer lots of questions about the effects of microgravity, radiation, etc. on the human body. That is not going to happen, so we have to take what we can get.
In this case, it has always been possible to look at the changes in an astronaut between pre and post space living. It is also easy to look at changes between people who live in space, and people who spend the same amount of time not living in space. What has not been done before is looking at these changes in the same genetic backgrounds—identical twins.
The identical twins are matched for genetics, age, upbringing, and tons of other things. They are also unique in many ways. One of the ways they are unique is in what they were doing for the time period in question; one lived in space and the other didn’t. It is extremely reasonable to conclude that living in space is responsible for some or all of the physical changes observed.
So, is the study flawed? Yes, absolutely, all studies are flawed. The question is, despite the flaws, does it provide useful information? In this case, the answer is yes it does. Maybe not because it is large enough to draw generalized conclusions, but because it is the first of its kind, and controls for things that previous studies have not been able to control for.
ETA plurality:
As somebody who works with twin data frequently, this is what I would say:
A member of a twin pair. (1 person)
A pair of twins. (2 people)
That family has twins. (2 people)
This is the twin data, it comes from MZ, DZ, and opposite sex DZ twins. (many people)
One of the twins from that family is scheduled for an interview. (1 person)
Please spend several pages talking about the appropriateness of data, datum, twin, and twins.
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### Author:  [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)
#### Post date: [April 12, 2019, 6:11pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/17 "2019-04-12T18:11:54Z")
> [@aceplace57](#):
>
> Ok, I must of been absent that day in English. 😉
I take it you were absent when the teacher taught that “must’ve” and _not_ “must of” is the contraction for “must have”.
As to your larger point, yes, both brothers have been on the ISS, but NASA knows exactly the condition of each at the start of the mission, so they know what changes resulted while one was on Earth and the other on the ISS.
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### Author:  [@aceplace57](https://boards.straightdope.com/u/aceplace57)
#### Post date: [April 12, 2019, 6:40pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/18 "2019-04-12T18:40:28Z")
It’s the long term changes from time in Space that I was thinking about. Mark Kelly is always going to be slightly different from someone who has never worked in Space. Scott has been there more recently and for longer. How much different? Prolonged exposure to Space is one of the purposes of the study.
Mark & Scott did get preliminary checkups and that is the baseline for the study.
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### Author:  [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)
#### Post date: [April 12, 2019, 6:54pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/19 "2019-04-12T18:54:39Z")
> [@Jasmine](#):
>
> Well, repetition is an important part of the scientific method. Repeating an experiment numerous times and compiling results from all of those experiments goes a long way in ruling out chance as a variable. In this particular instance, we have one set of twins and that’s it. Perhaps some of those changes/variances can be attributed to him as an individual. There’s no way of knowing for sure unless we repeat the experiments with, for example, 100 sets of twins.
This isn’t really true. While repetition is the hallmark of verifing scientific studies, the point of the twins study (I’m not getting to the tangent about grammar) was to look at factors already associated with changed in human physiology due to long duration spaceflight and assess what could be attributed to natural variation between unrelated people and what is likely associated with the difference in environment between two essentially genetically identical people, one of whom has had a limited exposure to the space environment and one who had about a year and a half. (Having a pure control would be desireable but NASA was exceedingly fortunate to have one set of twins.) So it wasn’t as if physiologists were just looking at differences blindly, but were actually looking for changes in the physiology and genome expression already observed in other astronauts and making comparative analysis between the twins in the study to verify that suspected effects due to exposure to the space environment are not just random variability or due to exposure to unquantified terrestrial conditions.
That we are not well adapted to the space environment—in particular, the effects of high energy cosmic radiation, the “microgravity” (freefall) condition, general stress, and long duration exposure to excess carbon dioxide and oxygen depletion—has long been expected and observed, but this study makes it possible to put some credible bounds on just how detrimental the space environment may be, and gives credence to the notion that long duration space habitation will require reproducing terrestrial-like conditions unless we can engineer the human body to protect or repair itself right down to the cellular and genomic level. It does not provide great confidence in the health of would-be Martian colonists; although we do not have any experience with long duration exposure at Mars’ 0.38 g gravity field, most space physiologists suspect that the threshold for maintaining adequate long term health is much higher (\>0.5 g), notwithstanding skeletomuscular and cardiovasuclar degadation in a lower gravity field.
This study was limited in scope and by necessity in a population of one control (with limited exposure) and one experimental subject so making any statistical assessment of effects is an exercise in handwaving, but the qualitative differences are dramatic and readily observed. There is no “flaw” in the study.
Stranger
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### Author:  [@ftg](https://boards.straightdope.com/u/ftg)
#### Post date: [April 12, 2019, 7:09pm UTC](https://boards.straightdope.com/t/is-nasas-kelly-twin-study-of-people-living-in-space-flawed/832442/20 "2019-04-12T19:09:27Z")
The part about the telomeres getting longer (they usually get shorter as we age) is interesting.
Now I know why there’s all these rich guys getting into the rocket business. 😉
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