Sex should be a routine consideration in the design
of animal research studies, results from one of the
largest ever studies of the effect of sex in
biomedical research suggest.
Whether we are male or female heavily influences the
prevalence, course and severity of many diseases
including cardiovascular and autoimmune diseases and
asthma, yet up until now the role of sex in animal
research has not been fully explored.
For consistency, most animal research is only done
on male animals.
In two-thirds of the research that uses both sexes,
sex is not factored into the analysis of the
To address this problem, researchers at the MRC
Harwell Institute, part of the International Mouse
Phenotyping Consortium (IMPC), performed one of the
largest studies to date on the effect of sex in
The study analysed up to 234 physical
characteristics in more than 50,000 mice.
Sifting through the data, the team found that in the
standard group of mice – the control mice –sex had
an impact on 56.6% of quantitative traits, such as
body weight, and on 9.9% of qualitative traits, such
as the shape of the whiskers.
In mice that had a gene switched off – the mutant
mice – sex modified the effect of the mutation in
13.3 % of qualitative traits and up to 17.7 % of
In many of these cases the sex of the animal was not
expected to have an effect.
According to the Harwell team, the research supports
the idea that - regardless of research field or
biological system - sex should be an important
consideration in the design and analysis of animal
One of the lead researchers, the MRC Harwell
Institute’s Professor Steve Brown, commented: “It is
likely that important scientific information is
missed by not investigating more thoroughly how
males and females differ in biomedical research.
Rather than extrapolate the results to account for
the opposite sex, these results suggest designing
experiments to include both sexes in the study of
This study is a major step to highlighting the
impact of sex differences in research and will help
in accounting for those differences in the future of
It is time that research studies reflect the
differences between men and women (2017-01-04)
How Being Male or Female Can Affect Your Health
For more information
Prevalence of sexual dimorphism in mammalian
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