Abstract
Optimal nutritional status is imperative for achieving the genetic potential for growth and development in children as well as for robust immune function and bone health in adults. Patients with thalassemia (Thal) are known to have abnormal growth, altered development and immune function and deficits in bone mass. For children, weight and height is commonly used to assess overall nutritional status, whereas for adults, body composition is a gross marker of an individual’s overall nutritional health. Nutritional status and body composition has not been explored in patients with Thal. To examine this, we have assessed body composition (fat, lean) and bone density by dual energy x-ray absorptiometry (DXA, Hologic Delphi A) in 370 subjects enrolled in a cross-sectional study of the Thal Clinical Research Network (TCRN), a North American collaborative research group. In addition to DXA, weight and height were measured, medical history obtained and a brief calcium food frequency and physical activity questionnaire completed. The total sample was divided into 2 groups: (TxThal) 257 transfused thalassemia major and E-beta thal patients (23.7 ± 11 yr, 131 male), and (NTxThal) 113 never or minimally transfused patients with other thalassemia syndromes (21.3 ± 13 yr, 50 male). Body mass index (BMI) was calculated (kg/m2) and cutoffs determined for children (<17=underweight, ≥30 obese) and adults (<18.5=underweight, ≥30 obese). As expected there was a high correlation between BMI and fat and lean mass by DXA (r=0.7 to 0.86, p<0.001). 6.2% of adults and 39.3% of children were classified as underweight by BMI and nearly 1/3 of children with Thal had abnormally low percentage body fat; while only 3.4% of adults and 2.2% of children were considered obese. Compared to median data from NHANES, adult patients with Thal are much leaner (BMI: 22.8±0.4) compared to contemporary adult Americans (28.1±0.2, p<0.0001). TxThal had more total body fat mass (14.3 vs 11.4 g, p<0.0001) and percentage body fat (27.3% vs. 24.9% p=0.007) compared to NTxThal. As has been observed in epidemiological studies of healthy subjects, calcium intake was inversely related to fat mass (p=0.009) as well as lean mass (p=0.007) after controlling for the effects of age, gender and diagnosis. Current physical activity level was a strong predictor of reduced body fat (p=0.007), whereas hemoglobin level was positively related to lean mass (p=0.001). Moreover, body fat was a positive predictor for height Z-score (p<0.0001). Low bone mass (BMD Z-Score <−2.0) was found in 50% of subjects, and BMD Z-score was moderately correlated with height Z-score (p<0.0001) and weight Z-score (p<0.0001). Though the majority of patients with Thal were classified as having a healthy body composition with very few obese patients, nearly 40% of the children in this sample were underweight. NTxThal appear at particular risk for underweight. These results suggest that an adequate amount of body fat is necessary for optimal growth and bone health in patients with Thal, and that calcium intake is associated with optimal body composition. These preliminary findings support the need for more careful study of nutritional status and its relationship to overall health in patients with thalassemia.
Effect of calcium intake and physical activity level on bone mass and turnover in healthy, white, postmenopausal women
