Why it matters: If you must cover an animal study, don’t forget this variable – News Block

lab rat

Photo by Janet Stephens. Public domain photo

Most health journalists have heard that they should never, or at least very rarely, cover animal studies when reporting on conditions related to human health. While some opposition While reporting on animal studies includes arguments about the ethics of using animal models in scientific research, the most prominent argument for most journalists is how closely or accurately the animal model can represent the disease or adverse effects or therapeutics in humans.

In 2006, US Secretary of Health and Human Services Mike Leavitt noted that “nine out of 10 experimental drugs fail in clinical trials because we cannot accurately predict how they will behave in people based on laboratory and animal studies.” A study in JAMA that year Similarly, it found that only a third of “highly cited animal research” translated into randomized human trials.

After all, humans are not mice, not rats, not pigs, not even monkeys. There will always be unique physiological differences between species that prevent full translation of findings from animal studies to humans. And it’s important to note that even if the characteristics between species were more similar, humans do not live in the artificial laboratory conditions of animal models.

key takeaway: If you are covering an animal study, pay attention to the environmental conditions of the laboratory animals and how those conditions may affect the results of the study.

Still, some circumstances warrant reporting animal studies, especially if there is no other effective way to investigate a particular scientific question. One such area is environmental health research that involves exposure to various chemicals. Since we can’t lock up a group of humans for 10 years and expose them to chemicals, animal studies can offer insight into the potential physiological effects of different compounds.

Consideration of these studies together with observational research in humans allows cautious conclusions to be drawn about the likely effects of certain environmental exposures. This approach encompasses most of the research about endocrine disruptor chemical products, For example. Animal studies may also help to elucidate how those effects occur, such as using rat research to understand how diethylstilbestrol causes cancer and infertility in women exposed prenatally to it.

what to look for

But here’s the rub: It’s those same studies where an often-overlooked variable can put a wrench in jobs. That variable is the laboratory animal’s environment: its enclosure, diet, water source, the containers used to feed and drink it, the room it is kept in, the temperature and lighting, etc.

So if you need to cover an animal study, especially one related to the effects of environmental exposures, pay close attention in the methods section to how the animals are housed, fed, watered, and cared for and whether any of those factors might play a role. in the results. If those factors are not described in the study, ask the authors about it.

To illustrate, I will offer some examples. An article (for a fee) by Jyoti Madhusoodanan in Nature last year examined how paying more attention to the diets of laboratory animals could improve studies. reproducibility — whose lack is already a big hurdle in scientific research. at its opening anecdoteshe describes how two different research teams produced different findings from what appeared to be the same study design, except that the different teams fed the monkeys different diets.

Or consider a study investigating the effects of a particular exposure in rats where the water bottles in the rats’ enclosures are not all identical. If some are glass and others the plasticchemicals leached from the plastic, which is actually been studied in rats, it could confound the results. Are any observed effects due to the chemical being studied or inadvertently due to the plastic bottles?

The story of the rat park

pet rats

Author Tara Haelle’s pet rats. Photo by Tara Haelle

My favorite example comes from a famous series of studies from the late 1970s and early 1980s called rat park. (Although I linked the Wikipedia article there for a quick summary, this excellent comic telling the story of Rat Park is much more entertaining.)

Before Rat Park, most research looking at animal self-administration of morphine involved keeping laboratory animals alone in small metal cages. But rats, like dogs, are social creatures that need enrichment, and Canadian psychologist Bruce Alexander wondered if the reason rats tend to choose morphine-laced water over plain water has more to do with their environment. austere.

So he built an enclosure 200 times the size of a standard cage and filled it with every rat’s dream: food, wheels, balls and other toys, more than a dozen rat friends, and plenty of room to run, explore, and mate. It turned out that the lab rats kept in this paradise had no need for morphine, even though the morphine water was sweetened, and they drank happily from the regular water bottle.

Although the fame of the experiment arose in large part from how changed the narrative of addiction — behold, the environment can influence the choice to self-medicate — the real intent of the research was to understand the importance of test conditions for laboratory animals. While Rat Park is an extreme example, many far flung places more subtle aspects of test conditions may affect the results. For example, mice and rats are nocturnal and light at nightas well as continuous exposure to light and even alone ambient noisethey can contribute to weight gain in rats (which, in turn, can increase the risk of multiple diseases).

The bottom line is that every little detail in a study can make a difference in the outcome. And when animal studies already have so many other hurdles to overcome to translate them to humans, it’s particularly important to pay attention to those details.


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