Prevalence and Complications of Obesity in Sickle Cell Disease.

Background: Obesity is associated with major health problems in the pediatric population and is a fundamental risk factor for adult obesity with its concomitant morbidities. Sickle cell disease (SCD) has historically been associated with poor nutritional status rather than obesity. Children with SCD, however, have many general risk-factors and disease-specific characteristics, such as ethnic distribution and sedentary lifestyle, that may increase their risk for obesity. We hypothesized that the prevalence of obesity in children and adolescents with SCD would reflect that of the general pediatric population and that obesity would be associated with demographic and disease-specific variables.

Methods: We conducted a retrospective chart review of all pediatric and young adult patients over the age of two in the Hasbro/RIH Sickle Cell clinics from 1980- 2008, collecting cross-sectional and longitudinal demographic and clinical variables. The primary outcome was the prevalence of overweight and obesity in this population. Secondary endpoints included the association of obesity with demographic and clinical variables and longitudinal growth trends. Body mass indices (BMI) were calculated for each subject, who were then categorized as underweight, healthy weight, overweight, or obese based on the International Obesity Task Force guidelines. Chi-square, Fischer exact tests, and T-tests were used to evaluate associations between overweight/obesity and the hypothesized risk factors and morbidities. Odds ratios were then calculated to determine the strength of these associations. This project was approved by the local Institutional Review Board.

Results: The analysis included 149 subjects with a mean age of 13.2±6.5 years, 51% male, and a mean hemoglobin of 9.7±1.8. The mean BMI was 20.5±6.3 with a range from 13.1–49.1. Five percent of the subjects were underweight, 70% healthy weight, 12% overweight, and 13% obese. The most common morbidities included acute chest syndrome (44%), frequent (>3/yr) pain crises (34%), asthma (17%), and obstructive sleep apnea (17%). Overweight and obesity were not associated with gender, race, or insurance status in this population. The overweight/obese group was significantly older than the non-overweight group (15.3 years vs. 12.4 years, p=.02). Obesity was associated with sickle cell genotype: subjects with less severe genotypes were more likely to be obese than those with the most severe genotypes (p<.01). Likewise, the mean hemoglobin was higher in the overweight/obese group than the non-obese group (10.3 vs. 9.5, p=.01). Obesity was also associated with a higher risk of certain SCD- and obesity-related morbidities including osteonecrosis (p=.01) and hypertension (p<.01). The overweight/obese group spent more time hospitalized over the past year than the non-overweight group (9.5 days vs. 2.1 days, p<.01). Overweight/obesity did not increase the likelihood of being on hydroxyurea treatment or requiring chronic transfusions, and did not increase the risk of acute chest syndrome, pain crises, asthma, obstructive sleep apnea, priapism, splenic sequestration, stroke, or abnormal transcranial doppler studies.

Conclusions: In contrast to traditional thinking, this is the first study to demonstrate a high prevalence of overweight and obesity in pediatric SCD. Indeed, the prevalence of overweight and obesity in our children with SCD parallels that of these conditions in the general pediatric population. In those with SCD, obesity is more common in patients with less severe disease and is more widespread in older children. Additionally, obesity is associated with increased risk of SCD-related morbidities such as osteonecrosis and hypertension and is associated with more hospitalizations.