We don't know a lot about how women experience diseases.

Understanding the timelines of diseases and how we can treat them is a part of the research. Most of it has been done on animals such as mice. The results from pre-clinical research on males apply to females as well.

Men and women have different experiences with diseases. How diseases develop, the length and severity of symptoms, and the effectiveness of treatment are included.

Smaller bodies?

The differences are not fully understood. Women are more likely to be worse off as a result.

It's the case for prescription drugs. More adverse reactions are experienced by women than by men. Many drugs are pulled from the market because of health risks for women.

Sex differences in body weight are thought to be the cause of drug reactions in women.

It is thought that if drug doses are adjusted according to body weight, women will receive lower doses than they currently do.

That might not be the case.

The assumption that females are smaller versions of males is not supported in most pre-clinical traits.

Drug reactions in women are not likely to be alleviated by changing the dose.

Adverse drug reactions are common and costly for healthcare

Women's healthcare decisions should be based on research conducted on men. The effects of adverse drug reactions are significant from both a clinical and economic point of view.

The healthcare system in Australia is estimated to cost over $1 billion a year due to hospital admissions related to medication.

Hospital stays have been shown to be shortened by drug reactions. Patients with an adverse drug reaction stayed in the hospital for a median of eight days.

Adverse reactions are the reason women stop taking their medication. Women would get more benefit from the healthcare system if drugs were weight-adjusted.

The weight of evidence

What evidence do we have to support the weight adjustment?

The sleep drug zolpidem is one of the drugs recommended by the FDA. The weight-adjusted dose for some drugs appears to work.

Drug reactions in women and men are related to what the drug does in the body. There are differences in how drugs are absorbed and cleared by the body between men and women.

A broad scale approach is required to get to the bottom of this. Evolutionary biology uses a method called " allometry" where a relationship between a trait of interest and body size is looked at on a log scale.

Over 2 million data points from the International MousePhenotyping Consortium were used to apply allometry analyses to 363 pre-clinical traits in males and females.

The most common disease model animal is mice. Sex differences in pre-clinical traits can be explained by body weight alone.

Sex differences can't be explained by weight differences. Some examples are iron levels, body temperature, and lean mass.

The differences between males and females could not be generalized because the relationship between a trait and body weight varied greatly.

Ignoring these differences in some cases, such as measures of blood cells, bone, and organs, could result in missing a lot of the population variation for a particular trait.

Sex differences need to be considered on a case- by-case basis.

One size does not fit all

Sex-based data is needed to advance care in an equitable and effective manner in an era where personalized medicine interventions are within reach.

Our study shows how males and females can differ in a number of pre-clinical characteristics, indicating that more needs to be done to measure how and in what ways the sexes differ.

Our data shows that dose-response is likely to be different for males and females when there is a relationship between sex and drugs.

The methods used in our study can help clarify the nature of the differences.

Laura B. Wilson and Shinichi Nakagawa are professors at the University of New South Wales.

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