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Forearm fractures account for a significant proportion of childhood injuries and appear to be increasing in incidence. Poor vitamin D status increases overall fracture risk in infants with rickets and adults with osteoporosis. Children with vitamin D insufficiency (serum 25-hydroxy vitamin D level < 20 ng/mL) have decreased bone mineral density (BMD) compared to children with normal vitamin D status. The relationship between vitamin D status and childhood forearm fracture has not been investigated.
This prospective study is enrolling African American children, ages 5–9 years, with a forearm fracture. Bone health evaluation includes measurement of serum 25-hydroxy vitamin D level and BMD by dual energy xray absorptiometry (DXA) scan. Univariable analyses are used to test the associations between fracture status and the independent variables serum vitamin D level and BMD.
Vitamin D levels are available for seventeen cases. The mean (± SD) 25-hydroxy vitamin D level is 20.1 (± 7.3) ng/mL with a range of 10–38 ng/mL. The mean of this group is at the cutpoint for vitamin D insufficiency. Ten cases (59%) were vitamin D insufficient. DXA scan results for these patients are consistent with normal bony mineralization for age.
A significant proportion of African American children with fractures in our study are vitamin D insufficient. Analysis of serum 25-hydroxy vitamin D levels and BMD in additional cases and controls will determine the significance of these findings.
Vitamin D insufficiency may play a previously unrecognized role in childhood fractures. Strong consideration should be given to routine vitamin D testing in African American children with forearm fractures.
Approximately half of all children will fracture a bone during childhood; of those, nearly 40% will sustain at least one additional future fracture.1 Skeletal fractures account for a significant proportion of childhood injuries2–6 and result in substantial costs and morbidity.7–9 Despite success in preventing other childhood injuries,10 fracture rates appear to be increasing.11–14
Prior fracture is associated with an increased risk of subsequent fractures during growth.15 Thus, there appears to be a vulnerable subset of the population at higher risk for fractures. Pediatric fractures are often attributed to normal childhood development, which makes falls and injuries common;16,17 however, there is increasing evidence that such fractures may be related to deficient bone health. Specifically, recent studies suggest that elevated fracture risk in otherwise well children may be a function of lower bone mineralization associated with both environmental factors, including poor nutrition and physical inactivity18–22 and genetics.23
Pediatric studies evaluating the role of bone health in childhood fractures have been primarily conducted in New Zealand and white children;19–21 yet, African American children may be at higher risk of bone health deficits, including vitamin D deficiency. Darker skin pigmentation is a risk factor for vitamin D deficiency;24 additionally, African American children have significantly lower dietary intakes of vitamin D compared with other ethnic groups.25 Limited published data reveal a high prevalence (up to 49%) of vitamin D insufficiency [serum 25-hydroxy vitamin D level < 20 ng/mL] in otherwise healthy African American children.26
The relationship between low vitamin D levels and fracture risk has been studied extensively in infants27–32 but its significance in children and adolescents has not been investigated. Recently, we have initiated a study of bone health, including environmental and genetic analysis, in African-American children with an isolated forearm fracture to evaluate the relationship between bone health and pediatric forearm fractures. Our objective is to determine the prevalence of vitamin D insufficiency and abnormal bone mineral density in a sample of African American children with forearm fractures.
A convenience sample of patients who satisfied the inclusion and exclusion criteria listed in Table 1 was enrolled between December 2005 and December 2006. This prospective study was conducted at Children's National Medical Center (CNMC), an urban pediatric medical center in Washington, DC. It represents a pilot study focusing on the enrollment of forearm fracture patients who will later represent cases in a case-control study. This subsequent case-control study will compare these patients to age and race-matched fracture free controls.
Patients were recruited through the outpatient Orthopaedic Clinic and were studied in the CNMC General Clinical Research Center. This study was approved by the CNMC Institutional Review Board. All participants and/or their guardians provided informed consent and children 7–9 years of age provided assent.
Bone health evaluation includes measurement of serum 25-hydroxy vitamin D level and bone mineral density by dual energy xray absorptiometry (DXA) scan. Univariable analyses are used to test the associations between fracture status and the independent variables serum vitamin D level and BMD. Data analysis was performed with SPSS Statistics 17.0 (SPSS Inc., Chicago, IL).
During the study period, seventeen cases have been enrolled. The mean (± SD) case age is 7.3 (± 1.3) years; age range 5 to 9 years; 53% are male. None of the patients were observed to adhere to a cultural or religious practice of wearing all enveloping clothing to cover exposed skin.
The mean (± SD) 25-hydroxy vitamin D level is 20.1 (± 7.3) ng/mL with a range of 10–38 ng/mL. The mean of this group is at the cutpoint for vitamin D insufficiency [serum 25-hydroxy vitamin D level < 20 ng/mL]. Ten cases (59%) were vitamin D insufficient. The proportion of patients with vitamin D insufficiency by season of enrollment is summarized in Table 2.
DXA scan results for all patients are consistent with normal bony mineralization for age (z-score > −2). The mean (± SD) total body z-score for study participants is 0.73 (± 0.8) with a range of −1.0 to 2.3.
There was no radiographic evidence of osteopenia for any of the patients.
Vitamin D is essential for calcium homeostasis and bone development/remodeling.33,34 Vitamin D deficiency has long been recognized as a cause of increased fracture risk associated with rickets in infants and osteomalacia in adults.33–35 This nutritional deficiency is more likely to occur in infants with darker skin, limited sun exposure, a history of breast feeding without vitamin D supplementation and poor dietary intake of vitamin D or calcium.24,36 This deficiency and its effects have been studied extensively in infants27–32 but its significance in children and adolescents has not been investigated.
There is an increasing awareness of a preclinical phase of vitamin D deficiency, i.e. vitamin D insufficiency,24,37 which increases the risk of osteoporotic fractures in adults.38,39 This term describes biochemical evidence of deficiency [serum 25-hydroxy vitamin D level < 20 ng/mL] without obvious clinical signs or symptoms, such as radiographic osteopenia.40 There is growing evidence that vitamin D insufficiency is a prevalent health problem. Surveys of other at-risk populations have shown that a significant proportion have vitamin D insufficiency41–44 which is associated with diminished bone mineral content.44
Vitamin D deficiency and/or insufficiency may also play an important but previously unrecognized role in fractures occurring in the pediatric age group. Few studies have investigated the effect of vitamin D intake, sun exposure, or vitamin D status on bone mineral density in children and young adults. However, in a 3-year prospective study of Finnish girls aged 9 to 15 years, girls with vitamin D deficiency had a 4% lower bone mineral density accumulation from baseline than did girls with normal vitamin D status.45 In adults, each standard deviation decrease in bone mineral density approximately doubles fracture risk.46
African American children are likely to be at higher risk of vitamin D deficiency and/or insufficiency. African American children have significantly lower daily intake of vitamin D compared with other racial/ethnic groups.25 Adequate intake levels for vitamin D from food are met by less than half of African-American children.25 The higher prevalence of lactose intolerance in this population may also contribute to nutritional deficiencies. In the United States, it is estimated that up to three fourths of African-Americans have symptoms of lactose intolerance.47 In addition, darker skin pigmentation is a risk factor for vitamin D deficiency.24
In our pilot data, 59% of African American children with fractures were vitamin D insufficient. This prevalence is higher than baseline levels of vitamin D insufficiency reported in comparable populations. The effect of these insufficient levels on fracture risk in otherwise healthy children merits further careful evaluation.
Interestingly, our preliminary results showed normal BMD measurements and normal bone appearance on radiographs for forearm fracture patients with and without vitamin D insufficiency. Analysis of serum 25-hydroxy vitamin D levels and bone mineral density in additional cases and controls will determine the significance of these findings. Vitamin D insufficiency may play a previously unrecognized role in childhood fractures. Strong consideration should be given to routine vitamin D testing in African American children with forearm fractures.
On the title page, include a paragraph which lists all forms of support, including pharmaceutical and industry backing. If you have not received grants or other aid, write: “None of the authors received financial support for this study.”
Paragraph summarizing forms of support/funding: This study is funded in part by the National Institutes of Health National Center for Research Resources (1K23 RR024467-01), Children's National Medical Center Bone Health Program, Children's National Medical Center General Clinical Research Center (5-MO1-RR-020359-02), Children's National Medical Center Board of Visitors and the DC-Baltimore Research Center on Child Health Disparities (5P20MD00165).
The authors have no conflicts of interest related to this article to disclose.
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