ORLANDO — Deficits in height, body mass index z scores, lean mass, and fat mass among children newly diagnosed with Crohn's disease carry implications for their long-term bone health, Dr. Meena Thayu reported at the annual meeting of the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition.
Treatment can improve some of these parameters, Dr. Thayu said.
Crohn's disease in children can cause chronic inflammation of the gastrointestinal tract, growth failure, and altered body composition. In addition, malabsorption can lead to nutritional deficiencies, including decreases in calcium and vitamin D, which may explain a higher risk of fractures in children and adults.
Other researchers found significant deficits in whole-body bone mineral content in 104 pediatric patients with Crohn's disease compared with 233 healthy controls (J. Bone Miner. Res. 2004;19:1961–8).
Another investigation in the same study population revealed lower height-for-age and BMI-for-age z scores among the children with Crohn's disease compared with controls (Am. J. Clin. Nutr. 2005;82:413–20).
“Crohn's disease subjects did not have the concomitant increases in lean mass with fat mass as the control children did,” said Dr. Thayu of the division of gastroenterology, hepatology and nutrition at the Children's Hospital of Philadelphia.
“These two cross-sectional studies … do not allow us to conclude the impact of the disease versus the impact of therapies,” Dr. Thayu said.
To address this, Dr. Thayu and associates studied 78 children within 2 weeks of diagnosis of Crohn's disease and 409 healthy controls. Participants were aged 5–21 years and did not have any chronic disease affecting growth.
The researchers assessed Tanner stage, disease characteristics, and body composition using whole-body dual-energy x-ray absorptiometry (DXA) scanning at baseline, 6 months, and 12 months after treatment initiated. “Although DXA is used widely clinically, it relies on two-dimensional data,” Dr. Thayu said. Therefore, they also performed peripheral quantitative CT on the tibia “which gives true trabecular bone mineral density and cortical dimensions, an indicator of bone strength.”
“Deficits in cortical dimension have a long-term impact on adult fracture risk,” Dr. Thayu said.
The Crohn's disease group had significantly lower Tanner scores, height, and BMI z scores than did controls. The affected group also had significant deficits in lean mass and trabecular bone mineral density versus the control group.
“Based on these findings, we were curious about any improvements after 12 months,” Dr. Thayu said. “So we launched a follow-up study.”
Preliminary results indicated changes in z scores for 29 children with Crohn's disease at a follow-up between 2.5 to 4 years after diagnosis.
“There is significant recovery in height and BMI. Interestingly, improvements in BMI are almost exclusively gains in fat mass.”
Modest improvements in lean mass were associated with improvements in trabecular density, Dr. Thayu said. In addition, those children with gains in lean mass were more likely to have improved clinical outcomes at follow-up.