Obesity in childhood increases risk of developing at least 6 different forms of cancer, study finds
Before Prof Baker initiated the CHILDGROWTH2CANCER project, researchers had been struggling to find large-enough population cohorts to yield results for non-breast cancers that could be generalised for all. ‘It’s not that researchers weren’t interested in other forms of cancer, it’s rather that breast cancer occurs earlier in life and is all too common, thus there were data material available that could support the studies,’ she explains. Prof Baker just so happened to have all the tools required to fill this gap. Looking to expand on her work on coronary heart and other diseases, she initiated CHILDGROWTH2CANCER with a view to contributing to this research field, using both advances in statistical modelling and theory as well as the data she had been working with for over 6 years. ‘Ideally, I needed cohorts with prospective measurements of body size in childhood, based on large numbers of individuals, with a long period of follow-up time, and for which I could reliably track the children into adulthood with minimal loss to follow-up,’ Prof Baker explains. Whilst very few cohorts fulfilled these criteria, the Copenhagen School Health Records Register — an electronic database that contains measured height and weight information on 372 636 children who were born from 1930-1989 and attended school in Copenhagen — ticked all the boxes. Using this data, she notably found that childhood body mass index and height have differential associations with many, but not all, forms of adult cancer; that child body size and growth may be linked to adult cancer through pathways other than adult body size; and that the risks for many forms of cancer begin at BMI values which are substantially lower than current definitions regarding child overweight and obesity. In other words, when it comes to cancer risk, common definitions of ‘overweight’ or ‘obese’ are too permissive. ‘Given that approximately 25-30 % of European youth are overweight or obese, our results suggest that far too many children may be facing a substantial burden of many forms of cancer in the future. Our findings also demonstrate that height is an indicator of risk for cancer. Even though height cannot be changed, it can be used by people to assess their own risks and change their behaviours to reduce their risks of cancer,’ Prof Baker says. With these results, Prof Baker provides evidence for what was otherwise a general feeling that body size matters for many forms of cancer. ‘I think our work is opening up the possibility that the origins of many forms of cancer lie earlier in life than previously thought. My hope is that our results will lead to investigations of genes and mechanistic studies to elucidate which processes contribute to the risks that we observed,’ she says. Although the project has now come to an end, Prof Baker says she will continue to work in this area: ‘We thoroughly investigated 13 different forms of cancer, but as there are more than 200 forms, a lot remains to be done,’ she explains. Besides this extension of project results, her plans also include projects aiming to examine how weight development across the life-course from infancy to adulthood is associated with a broad range of non-communicable diseases.
Keywords
CHILDGROWTH2CANCER, obesity, cancer, breast cancer, overweight, children, height
