What is your PhD thesis about?

“I used questionnaires to study different types of stress in pregnant women and examined stress levels in children by measuring the amount of the stress hormone cortisol in their hair. I then tried to determine whether there is a correlation between stress and various types of cardiometabolic disorders in children, such as overweight, obesity and abnormal blood pressure and heart rate. We also looked at where exactly in the body the fat is located, because there is a stronger correlation between belly fat around the organs and diseases that manifest in later life than there is between subcutaneous fat and such diseases.

“Scientists are also increasingly focusing on stress, because we’re learning more and more about its potential negative impact. We also know that children who are overweight or have high blood pressure at a younger age are much more likely to suffer such disorders in adulthood. If you know what causes children to have such disorders, you may be able to prevent them in future.”

Xavier Moors Traumaheli 4 – Levien Willemse

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So, what did you find?

“We saw that women who reported anxiety or stress while pregnant were more likely to give birth to children with overweight and increased body fat mass. Children of mothers who reported a high level of anxiety were also more likely to have higher fat levels in and around their organs. Interestingly enough, there was no correlation between depression in pregnant women and cardiometabolic disorders. Probably one of the reasons for this is the fact that anxiety and stress are caused by different mechanisms.

“We also found that children with higher hair cortisol levels were more likely to have a higher BMI, higher body fat mass and increased fattiness of the liver. Unlike cortisol measurements performed in blood, urine or saliva, hair cortisol is a good indicator for chronic stress. Hair grows by about one centimetre per month. We took small three-centimetre locks of hair from the backs of our subjects’ heads – you can’t tell – and measured their cortisol levels. This gave us an idea of each person’s average stress level in the past three months.

“Another thing I studied was DNA methylation, a complex mechanism that may affect the way genes function. This process may be affected by environmental factors such as smoking, nutrition and stress. We also know that there is a correlation between changing BMI and DNA methylation in adults, but this correlation was barely observed in children in a large international study led by us. So we think it’s possible that a person must be exposed to overweight for a considerable period of time for it to affect their DNA methylation.”

Generation R is the large-scale study of health and development in Rotterdam-based children and their parents, conducted by the Erasmus MC. What was it like to conduct your doctoral research as part of that program?

“I’ve really come to see the importance of such large-scale data studies, and more specifically, the importance of studies of the consequences of adverse conditions in people’s early lives, from the moment they were conceived to their second year. For instance, I think it’s interesting that a mother’s experiencing stress during pregnancy may have an impact on her child’s life. It’s great to be able to use the Generation R data to solve part of the puzzle.”

What was conducting research as part of the Generation R programme like in practice? Were you the person collecting people’s hair?

“In the first two years I was one of the persons collecting data at the study centre. Children and their mothers would come to us for three hours, during which time they’d visit five rooms for various types of measurements. I would collect blood, cut hair for cortisol measurements and get them to do a test on an exercise bike, among other things. In addition, I would often visit people at home, to do things such as making sure people stayed in the study and completed their questionnaires. It’s vital that we keep a varied study population. The Generation R study is a multi-ethnic cohort, which actually makes it interesting. Only it does take a little extra effort to continue reaching the entire population and activate them to take part. Which means you’ll end up having tea with a family, which is a lot of fun.”

You’ve completed your doctoral research project. What’s next?

“I’m currently training to become a general practitioner [family doctor]. I love making a difference to people’s lives at an individual level. Many symptoms and disorders such as diabetes, obesity and high blood pressure can be prevented to a considerable degree by a healthy lifestyle. As a GP, you can make quite a difference by giving people information and explaining things. An absolute fortune is being spent on the treatment and healing of diseases, even though only a fraction of the amount spent annually on healthcare is spent on the prevention of such diseases. In the section of my viva where I addressed the lay audience, I mentioned the fact that the global obesity percentage has nearly tripled in forty years, and this percentage is still increasing. In addition to the coronavirus pandemic, we’ve had an obesity pandemic for years now. This might not seem too urgent, but it is. If you continue to be overweight for years, your health will be severely impacted.”

You had twins while doing your doctoral research. Wow!

“Yeah, two boys. They’re 3 now. Sometimes it was a challenging combination, but most of the time, it was a lot of fun. For instance, while I was on maternity leave, I was supposed to submit two articles by a certain deadline, and I’d sit there hoping the boys would stay asleep in their playpen for a little longer.”