Discussion
To date this is the largest study looking at weight status in children
and adolescence with SCD. Mississippi currently has the highest
incidence of patients with sickle cell disease and also has the highest
pediatric and adult obesity rates in the nation at 25.4% and 39.5%
respectively(14, 15). In our sample, patients were more likely to be
overweight/obese (24.5%) versus underweight (4.4%). Our sample of
pediatric patients with SCD had a similar prevalence rate of overweight
as both state and national prevalence rates. Additionally, the combined
overweight/obesity rate for the current sample (24.5%) is comparable to
other published national overweight/obesity rates ranging from 22-25%
(15). Higher hemoglobin levels and lower absolute reticulocyte count
were significantly associated with a higher BMI.
Historically, poor growth, short stature, and being underweight have
been a concern in patients with SCD. Children with SCD are known to have
higher resting energy expenditure compared to control children and this
in part is associated with chronic anemia. Hemoglobin levels are highly
correlated (r = 0.7) with resting energy expenditure(4, 16). Our
current study found a significant relationship between increased
hemoglobin levels and increased BMI which is consistent with past
studies looking at improved growth in SCD. The Stroke Prevention Trial
showed that children with SCD who were chronically transfused to
maintain a hematocrit greater than 30% had significant improvement in
height, weight and BMI z-scores such that after 2 years of treatment,
they were of comparable size to their healthy peers(16). While we
hypothesized that hydroxyruea and chronic transfusion therapy would be
associated with increased BMI, current results did not support this
hypothesis. These relationships may be too complex to capture in
cross-sectional data, as patients on hydroxyruea and chronic transfusion
therapy tend to have the most severe disease and medical compliance, or
lack thereof, may impact results.
Overweight and obesity in otherwise healthy children is associated with
medical complications such as hypertension, dyslipidemia, insulin
resistance, dysglycemia, fatty liver disease and psychosocial
complications (17). Metabolic syndrome, which includes: increased waist
circumference, elevated triglycerides and fasting glucose and elevated
blood pressure is a key-risk factor for cardiovascular disease(16).
Prospective studies are needed that evaluate the consequence of
overweight and obesity on the health of pediatric patients with SCD. It
will be important to gauge the impact of elevated BMI on both morbidity
and mortality in SCD as medical interventions continue to improve for
SCD. This may ultimately impact guidelines for screening, as well as
nutrition and exercise guidelines for these patients.
Although this study has the strength of having a large sample size
(N = 781) and robust measurement of disease-related variables,
several limitations warrant discussion. The primary limitation is being
a retrospective cross-sectional chart review study. This type of data
has inherent limitations as it exists for clinical purposes and random
error in the data must be assumed. Additionally, a causal relationship
between increased hemoglobin and decreased absolute reticulocyte count
with increased weight status cannot be concluded with retrospective
data. Further, this sample is limited to pediatric patients with SCD in
Mississippi. BMI is strongly associated with genetic and environmental
factors such as individual and family diet and exercise patterns(18).
While current study results are similar to Chawla et al., (2013), these
results may not generalize to other pediatric patients with SCD across
the United States.