Low Vitamin D Linked to Forearm Fracture Risk in Children

Steven Fox

August 27, 2012

August 27, 2012 — Low vitamin D levels and bone mineral density may be risk factors for forearm fracture, according to results of a case-control study of 150 African American children, published online August 27 and in the September issue of Pediatrics.

"Because suboptimal childhood bone health also negatively impacts adult bone health, interventions to increase bone mineral density and correct vitamin D deficiency are indicated in this population to provide short-term and long-term benefits," write Leticia Manning Ryan, MD, MPH, from the Children's National Medical Center in Washington, DC, and colleagues.

Forearm fractures are on the rise among children. The authors note they are unique injuries that have been associated with low bone mineral density in both adults and white children, but the links between bone mineral density, serum vitamin D status (25-hydroxvitamin D), and risk for forearm fracture have not been studied in African-American children.

Factors associated with risks for forearm fracture, such as poor dietary intake of calcium and dairy products, are more common in African American children than in white children, the authors note. African-American children are also more likely than white children to be obese — another demonstrated risk factor for forearm fractures.

"Although African American children may be a vulnerable subset of the pediatric population, the relationship between forearm fracture risk and bone health has not been investigated in this group," the authors write.

From December 2005 to May 2011, the authors recruited 150 African American children aged 5 to 9 years. About half (n = 76) had sustained forearm fractures; the other half (n = 74) had not.

The researchers measured height and weight, bone mineral density, and 25-hydroxvitamin D status in both groups of children. They interviewed the children and their parents to find out about the children's diets and to get sociodemographic data and medical history. They also asked about how much outdoor play time the children engaged in each week, using that quantified measure as a proxy for exposure to the sun.

The authors report that the 2 groups were the same in terms of age, sex, parental education levels, season of enrollment, and the amount of time they spent playing outdoors.

Children with fractures had lower whole-body z scores for bone mineral density (0.62 ± 0.96 vs 0.98 ± 1.09; adjusted odds ratio, 0.38; 95% confidence interval [CI], 0.20 - 0.72) than children without fractures. Children with fractures also were more likely to be overweight (49.3% vs 31.4%; P = .03).

Compared with the control patients, children with fractures were also more likely to be vitamin D deficient (47.1% vs 40.8%; adjusted odds ratio, 3.46; 95% CI, 1.09 - 10.94), the authors report.

Another statistically significant difference in the 2 groups was that the children with fractures consumed more dietary calcium than children in the control group. However, the authors say, that probably reflects higher overall caloric intake in that group. In fact, the authors state, "when the daily calcium intake was expressed as a proportion of daily kilocalorie intake (as calcium nutrient density), there was no longer a significant difference present between the groups."

"To our knowledge," the authors write, "this is the first study in which the association between lower [bone mineral density] and increased odds of forearm fracture risk has been shown in African American children, a pediatric population that may be at higher risk for bone health deficiencies and fractures."

They say their results add to the growing body of literature suggesting that forearm fractures during childhood may be a marker of deficient bone health. Limitations of the current study include single site design, lack of non–English speaking participants, potential recall and reporting bias, a greater number of subjects with asthma in the control group, and no measurement of pubertal status.

"Because forearm fracture rates in children are increasing and bone health status in childhood may directly impact adult bone health, opportunities to intervene during childhood should be pursued," they conclude.

This study is funded in part by the National Institutes of Health National Center for Research Resources, the Children’s National Medical Center General Clinical Research Center, the Children’s National Medical Center Board of Visitors, and the DC-Baltimore Research Center on Child Health Disparities. The authors have disclosed no relevant financial relationships.

Pediatrics. Published online August 27, 2012.


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