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Why do we need large population studies?

January 26, 2017
Norwegian Institute of Public Health
Recently, both the US and UK had to shelve plans to start large population studies. In a new article, an expert argues that these large cohorts are more important than ever.

Per Magnus, director of the Norwegian Mother and Child Cohort Study (MoBa) at the NIPH, together with two researchers from the UK and Denmark, have written a commentary article in the latest issue of the journal JAMA Pediatrics. The journal is published by the American Medical Association.

The article is about the importance of large birth cohorts, such as MoBa.

Both the US and Britain have tried to launch similar birth cohorts, but have not succeeded. There are several reasons for this, both economical and practical.

Expensive and difficult

It is simply too difficult to collect data about the mother, father and children in these countries and it is very expensive. When the US survey -- the National Children's Study -- was shelved, it had already cost 1.3 billion US dollars and had been planned and tested on a small scale for over 15 years.

Denmark (the Danish National Birth Cohort, BSIG) and Norway (MoBa) have managed it, partly because we have a unified public healthcare system. In addition, we have very good health registries.

When neither the US nor the UK manage to get large birth cohorts up and standing, researchers wonder what we are missing out on, and how important these studies really are. It is now almost 20 years since BSIG and MoBa started.

The authors argue in their JAMA article that many of the important diseases that affect children would have been impossible to research without epidemiological data (biological data and questionnaire data) from these studies. These data include birth defects, childhood cancers, type 1 diabetes and autism in children.

Increased knowledge about disease

Thanks to these studies, we now know more about the significance that infections in mother and child have for development in utero and after birth. We also understand better the role that pollutants and diet play for child development, and the role genes play in the development of disease.

MOBA is a so-called prospective health study. This means we gather data from the mother, father and child when they are healthy. If illness should occur in the future, scientists can go back to the data and look for causal factors. This requires large surveys of more than 100,000 people. In MoBa, 114,500 children, 95,000 mothers and 75,000 fathers participate.

BSIG and MoBa have so far published more than 800 research papers. According to the authors, the most important discoveries relate to understandings about how chronic diseases in the mother during pregnancy affects the baby, and how the mother's intake of folic acid before and during pregnancy can prevent autism.

When it comes to research on cancer and type 1 diabetes in children, even MoBa and BSIG are too small. These studies have therefore collaborated with several other cohorts, including large cohorts from Asia, to obtain a better basis for research. One important collaboration is called The International Childhood Cancer Cohort Consortium (I4C).

Genetic causes

The authors argue that we now need large population studies more than ever before. They point to the importance that these studies have for finding genetic causes of disease and for investigating exposure to infectious diseases.

The authors conclude that although the United States and Britain have failed in setting up large birth cohorts, these countries can still play an important role in facilitating global collaboration between cohorts, such as the pediatric cancer initiative I4C. Countries can also be important sources for funding, such as through the National Institutes of Health (NIH) in the United States.

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Materials provided by Norwegian Institute of Public Health. Note: Content may be edited for style and length.

Journal Reference:

  1. Terence Dwyer, Per Magnus, Jørn Olsen. In the Aftermath of the National Children’s Study. JAMA Pediatrics, 2017; DOI: 10.1001/jamapediatrics.2016.3968

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Norwegian Institute of Public Health. "Why do we need large population studies?." ScienceDaily. ScienceDaily, 26 January 2017. <>.
Norwegian Institute of Public Health. (2017, January 26). Why do we need large population studies?. ScienceDaily. Retrieved May 27, 2017 from
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