EVIDENCE establishes that cardiovascular disease (CVD) risk factors seen in children are a predictor of cardiovascular events in middle age. The question for GPs and other physicians is what should be the next step?
A global team of researchers from the International Childhood Cardiovascular Cohort (i3C) reported this month in the New England Journal of Medicine that cardiovascular risk factors, when measured in childhood, strongly predict the occurrence of cardiovascular events in later life. The results were obtained from a 40-year follow-up study of 38,589 children from the United States, Finland and Australia.
Risk factors included those traditionally used to screen adults for CVD risk – blood pressure, serum lipids, body mass index, and smoking – factors that have been shown repeatedly in prospective cohort studies at adulthood as important predictors of later CVD.
However, no similar evidence is available for these same risk factors when observed in children. The reason for this is that obtaining this evidence requires a study of sufficiently large sample size and of very long duration, covering the period from childhood to the age when cardiovascular events begin to become common – middle age. The practical difficulties of setting up such a study seemed insurmountable until 2002, when Australian investigators, who had embarked on a follow-up of Australian schoolchildren interviewed in 1985, suggested that their American and Finnish counterparts pool the data from their cohorts and follow them for the occurrence of cardiovascular events at midlife. All cohorts began recruiting participants in the 1970s and 1980s and measured CVD risk factors at least once in childhood between ages 3 and 19.
The five risk factors in children associated with the risk of a cardiovascular event in adults – the majority of which were fatal or non-fatal myocardial infarction or stroke – were systolic blood pressure, serum cholesterol and triglycerides. , body mass index and smoking.
All risk factors in children were significantly associated with an increased risk of adult cardiovascular events, both fatal and non-fatal, with the hazard ratios for those with values above a clinically defined threshold – per example. High BMI or high cholesterol – ranging from 3.39 to 2.13. The risk among those who had more than one risk factor, identified by a risk ‘score’, was significantly higher than for just one risk factor. Children with combined risk scores in the top 5% of the distribution were estimated to have more than six times the risk of a cardiovascular event compared to children in the lower end of the factor distribution. of risk.
These estimated risks are reasonably similar to those seen in adults and are clinically meaningful.
The question that must be asked in an observational study of this kind is whether the observed associations should be assumed to be causal. The fact that early onset atherosclerosis is frequently present in children under 10 years old makes the conclusions highly plausible. The study design also makes it unlikely that commonly encountered biases could explain the results. Although individual risk factors were not adjusted for each other, the set of risk factors was adjusted for cohort location, socioeconomic status, and race. Loss to follow-up, which is a major potential source of bias in prospective cohort studies, is not a concern here because the high risks were found in the analysis that involved well-determined fatal events identified by registries of death.
Finally, in all observational studies, we are concerned that reverse causation, whereby disease causes changes in risk factors, may explain the results. In this study, risk factors were measured long before disease-related symptoms were likely to have been experienced.
We believe these findings should be taken very seriously, especially in the context of the childhood obesity epidemic, which has largely occurred since these cohorts began. The New England Journal of Medicine the editor wrote in a companion editorial to the main article:
“Whether [cardiovascular] risk factors can be identified early in life, we as clinicians have the ability to address health issues early and could dissociate the risk from an inexorable march towards cardiovascular disease and death. We’ve been waiting for hard data showing that risk factors seen in childhood predict future disease, and we now have a good start on cardiovascular disease.
The question, however, is what should be the next step?
Recommendations for policies and implementation strategies for childhood CVD prevention have been developed in recent years, but in a context where there was no certainty about the importance of CVD reduction. risk factors. A concerted effort to examine the effectiveness of various strategies to address the problem of CVD risk factors in children is now imperative. This effort must involve decision makers in government and health care to ensure that optimal approaches are identified and implemented.
Professor Terence Dwyer is Emeritus Professor of Epidemiology at the University of Oxford. He is a Professor at the Murdoch Children’s Research Institute in Melbourne and an Honorary Professor in the Department of Paediatrics at the University of Melbourne. He was the main author of New England Journal of Medicine document cited in this article.
Professor Alison Venn is Director of the Menzies Institute for Medical Research at the University of Tasmania.
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