(Washington DC) — US doctors have discovered that small changes in body-mass index (BMI) can make bigger differences in blood pressure among overweight and obese children compared with normal-weight kids [1]. Dr Wanzhu Tu (Indiana University, Indianapolis) reported the findings last week here at theAmerican Heart Association High Blood Pressure Research 2010 Scientific Sessions.
The effect on both systolic and diastolic BP of overweight children's BMI was over four times that of normal-weight children. "Clinicians should therefore pay close attention to already-overweight children, because BP in the prehypertensive or hypertensive range is a bad thing at such a young age and really sets the stage for later diseases in adulthood," Tu explained to heartwire .
Also, the findings have implications for future research, says Tu. Because BMI and BP studies typically don't separate normal-weight and overweight children, results will tend to overestimate the effects on BP in those of normal weight but underestimate the effects in heavier children, so "we have to somehow accommodate such differential effects going forward," he comments.
BMI Effects on BP Stronger Above the 90th Percentile
Tu and his colleagues tracked the blood pressure, height, and weight of just over 1000 children from local schools over time, with the mean age at enrollment being 10.2 years (range four to 17 years) and the longest follow-up exceeding 10 years.
"What we have done differently is essentially to provide two sets of estimates, one for normal-weight children and one for overweight and obese children," Tu told heartwire .
Children with BMIs in the 85th percentile or higher are considered overweight. "Below the 85th percentile, BMI effects on BP appear to be fairly linear," says Tu. But after the 85th percentile, and particularly after the 90th percentile, "BMI effects are noticeably stronger."
The message here is that parents and doctors need to pay close attention to children's weight, particularly if a child is already in the overweight or obese category, says Tu.
"For family physicians, if you keep seeing this child who already has increased weight, that should set off an alarm, you should look after the child more closely and be mindful not just that the child is heavier but also that there is a dramatically increased risk of hypertension."
"And because the BMI effect is so much greater in overweight and obese children, for a small reduction in BMI you might actually have a lot of benefit in BP; on the other hand, for a small increase, you could dramatically increase the risk of prehypertension or hypertension in children."
Commenting on the new findings in a European Society of Cardiology statement [2], Dr Joep Perk (Linnaeus University, Sweden) says: "Overweight children usually grow into overweight adults, with all the risks this carries of cardiovascular disease. The study reinforces that we must maintain our focus on relevant campaigns to promote weight loss and control in all sections of society, but particularly among the young."
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