Experimenting with healthy children?

Scientist measuring a child

Investigating children’s health sounds very benign. Moreover, the results may seem applicable to raising your own children. There is a catch though: how do we experiment with healthy children without running the risk of harming them? In this blog you’ll discover why ethics makes it important to pay close attention to the wording in advices on children’s health. Warning: this blog is a bit longer than usual.

The golden standard in scientific research

When we want to know whether physical activity affects health, we are interested in a causal relation between activity and health. Experimental research provides the strongest evidence for a causal relation and is considered the ‘golden standard.’

Experimental research follows the same procedure you would when testing whether a cake tastes better with more vanilla. You’d bake two cakes: one with more vanilla than the other such that you can taste the difference. The essence of experimental research is that the scientist manipulates the variable that is supposed to cause an effect – the independent variable – and measures the effect on a dependent variable.

experimental research is manipulation
Experimental research is manipulation

The golden standard may be too risky

Because the scientist manipulates his research subjects, for instance exposing them to physical activity or withholding it, all experimental research involves a risk of affecting the subjects negatively. Whether we consider this risk acceptable depends on a balance between risks and benefits.

When studying health, the risks are automatically big. Moreover, when studying healthy children, possible benefits for the participants are low. They are healthy already and have little to gain. There are two ways around this problem: research without manipulation and experimental research on sick children who have more to gain.

Solution 1: Epidemiological research

Epidemiological research does not involve manipulation, which minimises risks for participants. This type of research is about big data: collecting many data from many subjects for a long time. For instance, if we’d want to know whether physical activity improves children’s health, we’d follow many children for a long time and measure their physical activity and health. If children who are more active are healthier than this is a sign that physical activity is healthy.

The sign is pretty uncertain though until we have checked whether the conclusion wasn’t messed up by what we call a confounding variable. When ice cream sales rise, the number of children drowning also rises. Off course this wasn’t due to the ice cream but to the confounding variable of summertime swimming.

Statistical methods capture confounding variables quite well. Therefore many additional things are measured during a study: socio-economic status, education, etc. However, if a variable hasn’t been tested or accounted for, it can mess up conclusions unnoticed.

So the benefits of epidemiological research are that it is safe and that participants can be studied over a long time. The downside is that it doesn’t provide rock solid information about cause and effect.

collecting data during development
Epidemiological research involves collecting many data for a long time

Solution 2: Experimental research on sick children

When we want to know whether something can make sick children better, we accept greater risks because there is more to win. Moreover, sick children are probably easier to convince to participate in a research program than healthy children who have no reason to change what they are doing. Therefore a lot of research on the health benefits of physical activity has been done with children suffering from lifestyle-related diseases such as obesity.

This type of research does provide evidence on a causal relation between physical activity and health. However, the hard evidence is limited to the group studied: obese children for instance.

The wording in health advices reflects the evidence

In my previous blog, I wrote about the health effects of physical activity. Most of the research was based on epidemiological research or on research with children suffering from health problems such as obesity. I try to convey this in my wording: “activity is associated with health” for results based on epidemiological research and “physical activity reduces high cholesterol” for research on sick children. Most journalists also do this.

When reading about science, and thinking of how to apply the science in daily life, it is important to pay attention to these subtleties. If something reduces high cholesterol, it does not necessarily mean that it prevents high cholesterol. If activity is associated with health, physical activity increases the odds of being healthy but doesn’t provide a certain route to health.

Did you like reading about research methods? Also check my blog on fundamental versus applied research.




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