Mice and Scientific Studies

Even though we are part of the same species, men and women have many biological differences. This is something that should be common knowledge, and for most of us, it is. It is unclear then why most scientific studies use only male mice. Most of the studies that are going on right now use male mice exclusively. During a survey conducted back in 2011, it was discovered that medical research studies are five times more likely to use male specimens.

This is an issue since chemical reactions that are true for men do not have to be true for the rest of the species as well. Since human testing is still considered unsafe and illegal in most of the research conducted today the use of mice has become far too common. And this is an issue since it is not easy to predict how the reactions in mice might compare to the responses in humans. And leaving female members of the species out of the study makes the results even more unpredictable.


Some studies have shown that the sex of a participant in the study has an impact of more than 56 percent on quantitative traits. Additionally, it has an impact on about 10 percent of qualitative traits. This means that bone density and bone formation are all predetermined by the sex of the test subject. Add to that the fact that certain diseases are more common in females than in man, as well as the other way around.

For example, estrogen has protective effects on the cardiovascular system making women succumb to related diseases far later in life compared to men. After menopause, when the levels of estrogen start to decline, the risk of heart diseases rises.

Sadly, this is not new information. The issue is that the severity of the impact on the results has not been revealed yet. For this reason, a team of scientists took a look at 50,000 mice to determine the exact impact. They used 14,000 wild animals and 40,000 mutant mice. These mutant mice were genetically engineered to have one gene inactive for a study to show the role it plays.

What researchers discovered is that 17.7 percent of quantitative and 13.3 percent of qualitative traits were altered in some way due to the sex of the test subject. In some instances, scientists were able to notice differences only when looking at both sexes simultaneously. This all means men tend to gain more from these studies than women, and that medical advancements favor men much more.

Sex matters. You only need to take a look at the menstrual cycle to understand why. Humans who menstruate have organs that men do not. Due to the difference in hormones, they also metabolize drugs differently. It has become common for drugs to be pulled from shelves due to their adverse effects on women.

Another issue is that when female test subjects are used, they are used when they are in a state similar to men. This means they are either in menopause or in the period before ovulation or menstruation. This is done due to the hormones having too big of an effect on the studies.

And while the number of women used in the clinical trials has been raised from nine percent in the 1970s to 41 percent in 2006, women are still underrepresented in clinical trials. That number is even worse when looking at animal studies.

What this study does show is how often differences in traits occur because of the difference in the sex of the test subject. Mouse sex even influenced the effects of genetic modification, which means that males and females are different at even the base parts of their genetics. Using male mice shows only one side of the coin.

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