The study, presented today at the American Heart Association Scientific Sessions, found that the new risk factor -- called BMI rebound age -- indicates that the earlier in young childhood that kids reach their lowest BMI and then begin to gain body mass, the greater the chance of having adverse changes in known cardiovascular risk factors, which can show up as early as age 7.

The study was conducted by Thomas R. Kimball, M.D., a cardiologist at Cincinnati Children's Hospital Medical Center, and funded by the National Institutes of Health. It is believed to be the first study to examine the relationship of BMI rebound and cardiovascular risk factors in children, and it's the latest in a series of studies conducted by Dr. Kimball and colleagues at Cincinnati Children's that have been presented at major scientific meetings over the past two years, all leading to one inescapable conclusion: Measuring BMI is just as important in children as it is in adults.

"Adults measure BMI when they're trying to figure out how to lose weight and reduce their heart disease risk," said Dr. Kimball. "With children, measuring BMI and taking action if it's too high can actually help prevent heart disease from developing. Our studies, which have focused on the impact of childhood obesity on children's hearts, make a powerful case that there is a clear link between obesity in childhood and heart disease in later life. We think it's now well established that pediatricians must start measuring children's body mass index, as early as age 3."

That age is important, he noted, because BMI rebound occurs between the ages of 4 and 7. At this time, body mass index reaches its lowest point and then begins to rise. The earlier that rebound occurs in a child, the greater the likelihood that by age 7, the child will have higher blood pressure and insulin levels, increased left ventricular mass and left atrial size, and other cardiovascular risk factors, according to Jennifer Jaworski, lead author of the study and a third-year medical student at the University of Cincinnati College of Medicine.

Dr. Kimball's previous studies all confirm the dangers of childhood obesity in terms of heart disease risk. In 2001, two related studies showed for the first time that obesity in children directly affects structure and function of the heart, which could lead to increased risk for heart disease. A 2003 study suggested that certain abnormalities of the heart are more common in obese children than in children of normal weight.

A 2004 study showed that morbid obesity in children and adolescents directly affects the structure of their hearts and puts them at increased risk for future heart attack. Data from a study presented at the AHA Scientific Sessions in 2006 indicated that bariatric surgery for very overweight children at least partially reversed elevated left ventricular mass, a known risk factor for heart attack. And, a study presented at the American College of Cardiology annual meeting earlier this year comparing contemporary children with apparently normal health to their counterparts from a generation ago, found clear evidence that children today are at higher risk of heart disease due to increased left ventricular mass.

"There is a very clear picture here -- and a clear roadmap for pediatricians to follow," said Dr. Kimball. "We have to use BMI as a marker to identify children at risk -- and then when we identify those children, we have to take aggressive action to reduce the obesity that BMI reflects, so that we prevent an epidemic of heart disease in young adults in the next decades."

In their most current study, on BMI rebound age, Dr. Kimball and his colleagues enrolled 308, 3-year-old children in the study. The children were divided into three groups:

  -- Early BMI rebound age (below the 25th percentile)

	  -- Middle BMI rebound age (between the 25th and 75th percentiles)

	  -- Late BMI rebound age (above the 75th percentile)

	

	

	

Every four months, the researchers measured the children's height and weight. At age 7, the researchers obtained echocardiograms to determine left ventricular mass and left atrial size and laboratory tests to determine other risk factors. For boys and girls, earlier age of BMI rebound was associated with negative cardiovascular changes including high blood pressure and elevated left ventricular mass which is known to be a major risk factor for heart disease in adults.