Fractures and recurrent fractures in children; varying effects of environmental factors as well as bone size and mass

Background: Fractures are frequent in childhood and cause considerable morbidity. Previous reports have indicated a variety of potential contributors to fracture risk including low bone mineral content and density, milk avoidance, lack of exercise, asthma, obesity, and a high consumption of carbonated beverages. Aims: We wished to test the hypothesis that children who sustain recurrent fractures have a lower bone mass and a higher prevalence of underlying risk factors for fracture than those who fracture once or not at all. Methods: We studied 150 children aged 4-16 years: 50 who had suffered recurrent fractures, 50 who had fractured for the first time, and 50 fracture-free controls. Subjects underwent assessment of bone size and mass by total body (TB) and lumbar spine (L2-4) dual energy X-ray absorptiometry (DXA). Values were adjusted for body size, based on the control group measurements as unadjusted DXA values are substantially influenced by size in children. Anthropometry and grip dynamometry were carried out, and information about factors implicated in fracture aetiology such as milk intake, physical activity levels, asthma prevalence and carbonated beverage consumption were recorded using questionnaires. Results: Children who had sustained one or more fractures had a significantly lower BMC and aBMD at all sites than controls after conversion to size adjusted z scores (L2-4 BMC P=0.0002; 1-2-4 aBMD P < 0.0001; TB BMC P < 0.0001; Tb aBMD P < 0.0001); estimates for TB excluded fracture sites. There was, however, no difference in adjusted bone mass between children with one and those with recurrent fractures. Children with recurrent fractures had a significantly lower milk intake, lower levels of physical activity, a higher BMI, and a higher consumption of carbonated beverages than controls. The prevalence of risk factors was not, however, significantly higher than controls in children with a single fracture. Conclusions: Children with fractures have a lower bone mass for body size than children without fractures. Modifiable risk factors such as diet and exercise increase the risk of recurrent fractures. (c) 2006 Elsevier Inc. All rights reserved.