Birth Weight And Growth Patterns Linked To Heart Disease In Adulthood?

By Amy Pletcher

Coronary Heart Disease (CHD) is the leading cause of death in the United States, implicated in over 500,000 deaths and affecting 13 million Americans every year. The American Heart Association (AHA) lists a variety of well- known risk factors for CHD, including age, heredity, high blood pressure, insulin resistance and others. However, a study published in the October issue of the New England Journal of Medicine by David Barker of the Oregon Health and Sciences University suggests that the danger begins much earlier than commonly suspected.

Barker is the originator of the fetal origins hypothesis, the theory that the risk for diseases later in life can be affected greatly by health issues in early life. Barker proposes that CHD, type 2 diabetes, stroke, and hypertension all have roots in poor nutrition during prenatal life and infancy. The correlation between a low weight at birth and the risk of CHD as an adult is commonly accepted within the scientific community. But this study by Barker and his colleagues suggests that birth weight isn't the only determining factor in development of CHD. According to Barker's findings, weight gain patterns in childhood are related to the risk of developing CHD more than body weight at any given point.

The explanation for this lies in the fact that babies that are born small lack muscle, a condition that usually continues into childhood. If they then gain weight rapidly at any time to catch up to or surpass their peers, they probably develop a high level of body fat in relation to muscle. This imbalance can lead to insulin resistance, high blood pressure, high cholesterol and other known factors for CHD later in life.

Health records from about 2,000 people born in Helsinki, Finland between 1934 and 1944 include information about weight at birth, at every month between birth and the age of 2, and then again once a year through 2003. Barker and his colleagues used this information with height measurements to determine body weight relative to height, or body mass index (BMI). BMI is known to be highly correlated with percentage of body fat, making it particularly relevant to research in growth patterns.

What Barker and colleagues found is that if a child was born with a BMI below average but had gained weight to be within normal ranges by the age of 2, there was not an increased risk of CHD. However, if the child was underweight at birth and at age 2, but then gained weight and was at or above normal BMI levels by age 11, there was a 14 to 35 percent increase in risk of CHD in adulthood.

There is a variety of research supporting Barker's fetal origins hypothesis. One study found that for babies underweight at birth, for every kilogram increase in birth weight, there was a decrease of 23 percent in risk of CHD in adulthood. Other studies have tied low birth weight to diabetes and other problems later in life, effects that are compounded by carrying extra weight throughout life.

There remains some uncertainty, however, in specifically when and how the damage is done in terms of future risks. Research published in Circulation, the journal of the American Heart Association, acknowledges the inverse association between birth weight and CHD risk, but found that the risk was not dependent on size at any other time than birth. There is also a theory rapidly gaining support in the research community that the real risk factor for CHD is rapid weight gain at any point in development, not just after age 2.

Specifically, another article published in Circulation found that accelerated weight gain during infancy, even just within the first few weeks, can result in overweight, insulin resistance and other precursors to CHD decades later. So while Barker's study suggests that if normal BMI levels are achieved by age 2 the risks of CHD are lessened, other research suggests that damage is still being done.

Regardless of specific mechanisms, almost all of the researchers in this area agree on ways to decrease the occurrence of CHD. Women who are pregnant or thinking of becoming pregnant need to maintain proper nutrition in order to decrease the risk of low birth weight. Also, infant growth rates need to be monitored and controlled to make sure that weight is being put on at the appropriate rate and is being fueled by good nutrition. These steps will help infants and children achieve a proper balance of muscle and fat, a proportion that may help keep them healthy throughout their lives.

Amy Pletcher is pursuing a master's degree in technical communication with a concentration in science news and writing at the University of Washington.