By Josh Grossberg

The frequency of childhood infections is a determinant of adult height, according to a new study recently conducted by a team of researchers from the Keck School of Medicine of USC led by Wendy Cozen, professor of preventive medicine and pathology, and conducted by Amie Hwang, post-doctoral fellow.

The study, published in the April issue of the American Journal of Epidemiology, is important because increased height is positively associated with some types of cancer, including breast cancer and lymphoma, and negatively associated with cardiovascular disease and stroke.

According to Cozen, genetic factors are determinants of adult height, but nongenetic factors can also contribute. “Researchers assumed that taller height was a surrogate measure for improved childhood nutrition, including higher fat and protein. But we suspect that cumulative childhood exposure to infection also plays a role in determining adult height, and thus may be an underlying causal factor for some adult diseases correlated with height.”

Other researchers from the Keck School included Thomas M. Mack, professor of preventive medicine and pathology; Ann S. Hamilton, associate professor of preventive medicine; W. James Gauderman, professor of preventive medicine; Myles G. Cockburn, associate professor of preventive medicine; statistician John Zadnick; and postdoctoral fellow Kristin A. Rand.

Identical twins who differed in height by at least one inch were identified from a cohort of California-born twins in a database developed and maintained by Mack and colleagues. From interviews with the twins’ mothers, the investigators found that the twin who had more infections was twice as likely to be the shorter twin. The effect was especially strong for infections in the toddler years.

While height itself does not cause illness, it can act as a signpost of risk of other conditions — including some cancers — that may be traced back to childhood infections. “The significance isn’t about height per se,” Hwang said. “Height is used as a surrogate for other adult diseases.”

The study is adjusted to take nutrition, weight and other factors into account.

Other studies have looked at the relationship between childhood infections and growth in developing countries in areas of extreme poverty, but this research suggests that a connection also exists in “a generally healthy, economically developed country.” According to the authors, a possible explanation for the effect is diversion of energy from the growth process toward fighting infection.

“Because the balance between energy allocated for immune function and growth must be carefully maintained, ill children may spend their energy fighting infection instead of increasing long bone length, resulting in shorter adult height,” the report states.

None of the mothers interviewed for the study suspected that illness played a part in her children’s height difference. The study may offer new leads on the importance of childhood experience on adult characteristics and possibly adult disease.