"Leg length is not the issue. Some factor that affects leg length may also affect the development of diabetes," Asao says. "The issue is how good a marker is upper leg length? Our findings suggest a possible relationship between early growth and chronic disease later in life."
Researchers used data on 8,738 black, white and Hispanic men and women from the Centers for Disease Control's Third National Health and Nutrition Examination Survey (NHANES III). The participants were grouped by race and gender, then compared based on their upper leg length (ULL) and glucose tolerance: normal glucose tolerance, impaired glucose tolerance and whether they had diabetes.
"We found an inverse relationship between upper leg length and having either diabetes or insulin resistance, meaning shorter ULL was associated with the two metabolic conditions," Asao says. The average ULL for men and women with normal glucose tolerance was 40.2 centimeters (cm), compared to 39.1 cm for those with impaired glucose tolerance and 38.3 cm for the diabetic group.
After adjusting for other risk factors, the inverse association remained for white women and Mexican-American women, but not for blacks or men. For each centimeter less of ULL, white women were 19 percent more likely to have diabetes, and Mexican-American women were 13 percent more likely to have it.
Body stature is determined by both environmental and genetic factors. Upper leg length is considered a marker for growth in childhood, especially before puberty, says Asao.
While standing height is correlated with upper leg length, it is not linked to higher risk for diabetes or insulin resistance once other factors are considered, she says. "We did investigate the ratio of upper leg length to standing height and found that it is significantly associated with diabetes and insulin resistance. Upper leg length, more so than standing height, is a marker of growth specific to a certain time period of life."
From gestation through childhood, bodies grow in a somewhat predictable fashion in the order of head, trunk and legs. "Newborn babies have a larger proportion of head to the total length of their body. Along the path of development and growth, that proportion gets smaller. Much of the increase in leg length occurs after birth, during childhood," she explains.
Two previous studies in Europe that looked at overall leg length and stature found an association between shortness and a higher risk of developing diabetes and insulin resistance. "This is the first study to examine this question in the U.S. population, and the first to concentrate on upper leg length (ULL)," she says.
The researchers adjusted for age, body weight, family history of diabetes, education, income, physical activity levels and lung function.
Co-authors are WH Linda Kao, Ph.D., M.H.S.; Kesha Baptiste-Roberts, Ph.D., M.P.H.; Karen Bandeen-Roche, Ph.D.; Thomas Erlinger, M.D., M.P.H.; and Frederick Brancati, M.D., M.H.S.
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