Obesity in Pediatric Sickle Cell Disease: A New Phenomenon
Obesity in Pediatric Sickle Cell Disease: A New Phenomenon
The objective of this project is to determine the prevalence of hypertension, hyperlipidemia
 and hyperglycemia in the pediatric population with sickle cell disease who are obese in
 Mississippi compared to those pediatric patients with sickle cell disease who are not
 overweight/obese. The pediatric hematology department at the University of Mississippi
 Medical Center (UMMC) has a relatively large population of patients with sickle cell disease
 who are overweight and obese. This is a paradoxical trend since high-energy expenditure of
 the body to produce new red blood cells usually results in underweight to normal weight
 patients. From our previous chart review, the investigators found our pediatric patients with
 sickle cell disease to have similar rates of overweight and obesity to that of state and
 national levels. The metrics our team will measure include: blood pressure, blood cholesterol
 levels and blood glucose levels. The investigators expect to find higher rates of
 hypertension, high cholesterol and high glucose levels in the overweight and obese patients
 with SCD compared to that of underweight and normal weight. Our ultimate goal for follow up
 projects will be to determine the baseline risk of hypertension, hyperlipidemia and
 hyperglycemia in this population so we can then determine effective, sustainable
 interventions for weight and the co-morbidities that come with increasing weight status. Our
 goal would also be to educate the patient and families on these interventions and provide
 them with resources, which could lead to an overall improvement in health and patients
 quality of life.
SIGNIFICANCE Sickle Cell Disease (SCD) is the most common genetic disorder in the world and
 in the United States (U.S.), with about 1 in 13 African Americans born with sickle cell trait
 and approximately 100,000 individuals currently living with SCD. In this disease, irregular
 shaped red blood cells (RBC) termed sickle RBC, get trapped in the microcirculation thereby
 causing ischemic organ damage throughout the body. Due to the chronic hemolysis (breaking of
 RBCs), patients with SCD have traditionally had a high basal metabolic rate and increased
 energy consumption (measured by resting energy expenditure) resulting from rapid production
 of new RBCs. Therefore, patients with SCD tended to be underweight and did not experience
 weight-related comorbidities such as hypertension, dyslipidemia and hyperglycemia. In recent
 years, there has been significant improvement in the medical management for patients with
 SCD, which has resulted in improved morbidity and mortality and increased life span. With
 these advancements in medical management, recent research has begun to describe increased
 rates of overweight and obesity in both pediatric and adult patients with SCD. Our research
 team's pilot data in Mississippi shows that 24% of our pediatric patients with SCD are
 overweight or obese, defined as body mass indexes (BMI) ≥ 85th percentile. Overweight and
 obesity is a new medical phenomena in SCD.

 The two leading causes of death in individuals with SCD are cardiovascular disease and
 stroke. In 1973, Lemuel Whitley Diggs estimated a median survival of 14.3 years for
 individuals with SCD, with 20 percent of deaths occurring in the first 2 years of life.
 However, as a result of improved medical management, patients with SCD are living longer. In
 1994, life expectancy had increased to 42-48 years for the most severe SCD genotype HbSS, and
 60-68 years for the less severe SCD genotype HbSC. Since patients with SCD are no living
 longer and overweight and obesity is a new phenomenon in SCD there is very little knowledge
 regarding its clinical impact on precipitant risk factors (i.e., hypertension,
 hyperlipidemia, and hyperglycemia) for cardiovascular disease, stroke, and overall morbidity.

 The two published studies to date have been in adults with SCD and document that overweight
 and obese weight status is associated with metabolic syndrome, hypertension and dyslipidemia
 resulting in a higher risk for cardiovascular disease and stroke. Type 2 Diabetes (T2D) has
 historically not been clinically documented in patients with SCD. Yet, recent studies have
 shown that the prevalence of T2D in adult patients with SCD now approaches that of their
 healthy African American counterparts. The same study showed that the risk of stroke and
 overall morbidity for patients with both SCD and T2D was significantly higher compared to
 patients with just one disease. It is critically important to assess and characterize these
 potential increased risk factors for cardiovascular disease and stroke in pediatric patients
 with SCD.

 Accurate Measurement of Outcomes in SCD In order to accurately assess weight-related risk
 factors for cardiovascular disease and stroke (i.e., hypertension, hyperlipidemia, and
 hyperglycemia) in pediatric patients with SCD, research is needed that appropriately adjusts
 for disease-related blood processes. Specifically, individuals with SCD have lower systemic
 blood pressures compared to individuals without SCD. In adults with SCD, clinical problems
 are observed with blood pressures at or greater than the 90th percentile. When utilizing the
 90th percentile, rates of hypertension are similar in adults with SCD (40%) as their healthy
 counterparts. It is thus recommended that blood pressure values be assessed relative to the
 lower values expected for patients with SCD, and that a lower threshold of ≥ 90th percentile
 be used to define 'relative hypertension' in individuals with SCD. Unfortunately, there are
 no current published age, sex and height-matched norms for blood pressure in youth with SCD.
 To robustly characterize the association between weight status and elevated blood pressure,
 the current study will utilize published age, sex and height blood pressure norms for healthy
 youth without SCD but define relative hypertension (primary outcome) ≥ 90th percentile.

 Overweight/obesity is associated with impaired glucose intolerance and is a strong predictor
 of development of T2DM, which increases the risk for cardiovascular disease and stroke.
 Specifically, early development of T2DM leads to significant microvascular and macrovascular
 complications in early adulthood. The greatest risks for impaired glucose tolerance in
 children is weight status (overweight and obesity) and family medical history of overweight
 and obesity. Screening for hyperglycemia and insulin resistance in high-risk youth is
 recommended, as children are often asymptomatic. Expert committees and the American Diabetes
 Association have endorsed the use of fasting plasma glucose or HbA1c for screening those who
 are overweight or obese (BMI > 85th percentile), staring at age 10 years of age. However, the
 use of HbA1c for glucose tolerance testing in SCD is not reliable due to the shortened life
 span of RBCs in SCD. Therefore, fasting glucose levels and serum fructosamine are recommended
 for patients with SCD. Fructosamine is a glycated protein and predicts glucose levels over a
 period of approximately 3-4 weeks and will be used as the primary measure of hyperglycemia
 (secondary outcome) in the current study.

 Similar to lower systemic blood pressure, individuals with SCD have historically been shown
 to have low cholesterol levels due to high levels of hemolysis and consumption of the lipids
 for new membrane synthesis. The estimated overall prevalence of dyslipidemia in all children
 in the US is 20.3% and increases to 42.9% in youth with obesity. With current treatments
 decreasing hemolysis and overall turnover of RBCs it is unknown if the medical community will
 start to see an increase in hyperlipidemia (secondary outcome) in pediatric patients with
 SCD.

 Key Risk Factors for Overweight/Obesity Though reasons for the development of
 overweight/obesity in the general pediatric population are multifaceted, energy imbalance
 (e.g., consuming more calories than exerted through physical activity) has the most research
 support and identified areas for intervention. Children spend about 15 minutes a day engaged
 in moderate-to-vigorous physical activity, far less than national recommendations of 60
 minutes a day. Children also spend over 85% of their time in sedentary activities, which is
 associated with increased weight status. Additionally, very few children eat a diet
 consistent with national guidelines and instead consume large portions of high-calorie,
 nutrient-poor foods and sugar-sweetened beverages, all of which are associated with weight
 gain and obesity. These problems are especially severe in Mississippi, which has the highest
 rates of physical inactivity and obesity in the U.S. In addition, African American youth
 demonstrate the highest rates of sedentary activity. Finally, family history of obesity,
 hypertension, hyperlipidemia, T2D, and maternal history of diabetes during pregnancy are
 significantly associated with increased risk for being children being overweight/obese.

 To begin addressing these gaps in knowledge, the investigators will evaluate blood pressures,
 hyperlipidemia, and hyperglycemia in pediatric patients with SCD who are overweight/obese
 compared to pediatric patients with SCD who are underweight/normal weight. We will further
 evaluate diet, exercise, and family medical history as key risk factors for
 overweight/obesity, hypertension, hyperlipidemia, and hyperglycemia in this population. If an
 increased risk for hypertension, hyperlipidemia and/or hyperglycemia is found related to
 overweight/obesity, it will be important for future prospective studies to examine the
 clinical impact on traditional complications of SCD, including cardiovascular disease,
 stroke, vaso-occlusive crises, acute chest syndrome, and neuropathies. This knowledge will be
 critically important as hypertension, hyperlipidemia and hyperglycemia are all risk factors
 that can be modified with pharmacologic intervention and/or behavioral lifestyle changes such
 as dietary counselling and exercise. This new knowledge can further lead to updated screening
 recommendations, as there are currently no standardized guidelines for screening for
 hypertension, hyperlipidemia and hyperglycemia in pediatric patients with SCD.

 Planning Phase: The first phase of the study will include 2 months for Research Nurse
 training, obtaining study supplies, and finalizing IRB approval (which will be submitted
 within two weeks of grant submission). Our team anticipates starting participant enrollment
 in October 2020 and plan to complete enrollment by August 2021. Study recruitment will occur
 for 8 months of the 1 year study period. The final two months of the project will be
 dedicated to data analysis, manuscript preparation and additional grant applications.

 Study Participants (N=200): The UMMC Pediatric Sickle Cell Clinic is the only specialty
 pediatric SCD clinic in Mississippi. It is one of the largest pediatric SCD programs in the
 nations, serving approximately 800 patients annually throughout the state of Mississippi.
 Pediatric SCD clinic is held twice weekly on the UMMC main campus in Jackson, MS. There is
 also a multidisciplinary clinic twice monthly and satellite clinics in Hattiesburg, Meridian
 and Gulfport, MS. Pediatric patients and a primary caregiver/parent (parent) (>21 years old)
 will be recruited from the UMMC main campus. Approximately 300 pediatric patients with SCD
 ages 10-19 years were seen in clinic in 2019. Dr. McNaull and Dr. Karlson have an approximate
 80% recruitment rate to single-visit research studies in this population. Thus, the
 investigators do not anticipate any difficulty with recruitment for the current
 cross-sectional study.

 Our team will recruit 60 youth who are underweight/normal weight and 60 youth who are
 overweight/obese, along with a parent for each youth.

 Biological Variable: The following biological variables will be extracted from the
 participants electronic health record (EHR): age, sex, SCD genotype, and pubertal status
 according to Tanner Stage criteria. Tanner stage will be determined by the regular medical
 provider at the clinic visit and extracted from the EHR. SCD occurs equally in males and
 females. Thus, males and females will be recruited in equal numbers.

 Methods: Recruitment: All study procedures will be completed at youth's regularly scheduled
 hematology appointment. A SCD research nurse coordinator will call potentially eligible
 families (based on age, SCD genotype, and clinic visit history) one to three days prior to
 their clinic visit as youth need to come fasting for study-related lab draws at their
 appointment. If families are interested in the study, then the procedures will be explained
 over the phone. The research nurse coordinator will be present in clinic the day of the
 youth's appointment to explain procedures in detail, enroll youth participants and a parent,
 and obtain written informed consent, permission, and assent. Procedures: After providing
 consent, the parent will complete two electronic questionnaires in REDCap on iPads (5-15
 minutes to complete). One questionnaire will be the Family Nutrition and Physical Activity
 (FNPA) screening tool to assess youth's nutrition and exercise. The second questionnaire will
 be a family history evaluation of the most common family risk factors for overweight/obesity
 and its co-morbidities. Blood pressure measurement will be taken three times in concordance
 with the 2004 New Task Force Report on High Blood Pressure in Children and Adolescents. Youth
 participants will then complete study blood collection during regularly scheduled clinical
 venipuncture blood draws (15 minutes).

 Assessments: Body mass index z-score (BMI z-score) will be calculated at the study visit
 using height (cm) and weight (kg). Trained nurses will take height to the nearest 0.1cm using
 a standard Stadiometer and weight to the nearest 0.1kg on a calibrated electronic scale while
 the children are wearing light clothing and no shoes. BMI will then be calculated by dividing
 the weight in kilograms by the height in square meters (kg/m2) and then be converted to BMI
 z-score based on age and gender norms. The BMI percentile will be charted using current
 Pediatric Center for Disease Control guidelines, with underweight defined as <5th percentile,
 normal weight 5-85th percentile, overweight defined at BMI >85th percentile and obese defined
 as >95th percentile.

 Blood Pressure Measurements: Systolic and Diastolic blood pressures will be collected
 according to recommendations of the 2004 New Task Force Report on High Blood Pressure in
 Children and Adolescents using the proper cuff size with routinely calibrated automated blood
 pressure monitors (SphygmoCor version 8.0, AtCor Medical). Youth will be seated comfortably
 at rest for 5 minutes with feet flat on the floor. Measurements will be made on the
 non-dominant arm supported at heart level and will be taken 3 times, one minute apart. The
 first measure will be used for adaptation purposes and the mean of the second and third
 measures will be recorded and used for analyses The median and 90th percentile blood pressure
 in over 1500 children with SCD has been previously published although it did not take into
 consideration height or include data for each year of age individually. Pre-hypertension,
 termed relative hypertension in SCD, is defined as blood pressure greater than the 90th
 percentile but less than the 95th percentile. This new clinical recommendation of using the
 90th percentile blood pressure to define hypertension in pediatric SCD will be used in the
 current study.

 Blood pressures for all participants will be classified using the National High Blood
 pressure Education Program (NHBPEP) Working Group on Children and Adolescent. For our study,
 (1) Normotensive will be assigned to patients with systolic blood pressure <90th percentile
 and (2) hypertensive will be reported as any patient with blood pressure >90th percentile for
 age, sex and height.

 Laboratory Blood Draws: Peripheral blood (10 mL) will be collected at scheduled blood draws
 in green and red top heparinized tubes. Blood will be sent to the laboratory at UMMC for
 analysis and send out lab analysis to Mayo Clinic Laboratories. The following laboratory
 analyses will be obtained: CBC, Reticulocyte count, lipid panel, fasting glucose and
 fructosamine. CBC, reticulocyte count and glucose are laboratory tests that are taken at
 regular scheduled appointments as a part of maintenance SCD care. Lipid panel and
 fructosamine are additional tests.

 Hyperlipidemia: Fasting lipid panel which includes total cholesterol, LDL, HDL and
 Triglycerides will be obtain from blood samples from each participant. Each participant will
 be classified into 1 of 3 risk groups for total cholesterol and LDL lipid panel. Risk groups
 are defined as follows: (1) Acceptable level <170mg/dL and<110mg/dL for LDL (2) borderline
 level 170-199mg/dL and 110-129 mg/dL and (3) High level >200mg/dL and >130mg/dL for total
 cholesterol and LDL respectively. HDL and triglyceride levels will be stratified by
 percentile based on age and sex. All reference levels are in concordance with lipid screening
 guidelines from the AAP which were adapted from the Lipid Research Clinic Pediatric
 Prevalence Study.

 Hyperglycemia: Both fasting glucose and serum fructosamine will be drawn to assess for
 hyperglycemia. Participants will be categorized by fasting glucose: (1) Normal glucose
 80-100mg/dL (2) Elevated glucose 101-125mg/dL (3) Hyperglycemia >126mg/dL. Impaired fasting
 glucose included any subject with glucose >100mg/dL. Serum fructosamine levels will be
 categorized into (1) Normal levels 203-263umol/L and (2) Elevated >263 umol/L.

 Questionnaires: Parent participants will complete the below questionnaires. Food and Exercise
 Survey: Parents will complete the 20 Question Family Nutrition and Physical Activity (FNPA)
 screening tool to assess youth's nutrition and exercise. The FNPA instrument was developed at
 Iowa State University in collaboration with the Academy of Nutrition and Dietetics following
 a comprehensive evidence analysis examining the influence of physical activity, sport
 participation, television viewing and video games for their influence on child adiposity.
 Initial validation was performed in a sample of 854 children and their parents in Des Moines
 Iowa. Correlational analysis and logistic regression were used to examine associations among
 FNPA factors and the relationship between these factors and child weight status. Significant
 correlations were found between BMI and seven of the ten constructs (breakfast/family meals,
 modeling nutrition, high calorie beverage intake, television in the bedroom, parent physical
 activity, child physical activity and sleep schedule) as well as between BMI and the overall
 FNPA score.

 Family History Survey: Parents will complete a short family history survey of the most common
 family risks for overweight and obesity which include: maternal history of BMI greater than
 the 85th percentile, maternal history of gestational diabetes, family history of
 overweight/obesity, family history of hypertension, cardiovascular disease, high cholesterol,
 and T2DM.

 Medical Chart Review: In addition to the biological variables above, the following variables
 will be extracted from the participants EHR from the current clinic visit: demographics
 (race, insurance payer), history of acute chest, asthma, obstructive sleep apnea, avascular
 necrosis and stroke, medications, disease severity score calculated based on number of ED
 visits and hospitalizations during the past 3 years. BMI and clinical visit laboratory
 results (hemoglobin, reticulocyte count, random non-fasting glucose) over the last 3 years.

 Potential Problems and alternative strategies: Recruitment and retention. Despite COVID-19,
 all pediatric SCD are operating in-person at full capacity. To maximize recruitment and
 retention, the study nurse coordinator will customize recruitment materials and strategies
 (e.g., study brochure, visual aids, and confirming Medicaid transportation to appointment).
 The investigators will use compensation and methodologies (research paired with medical
 appointments) effective for ≥80% recruitment in previous cross-sectional studies with this
 population [e.g. Physical Activity and Pain in Youth with Sickle Cell Disease. While the
 investigators do not anticipate problems with recruitment, the team will plan to add the
 Meridian and Hattiesburg satellite clinics if 30% below recruitment goals in Month 3. Age
 range. Another potential concern is the broad age range of 10-19 year olds, with differences
 in weight potentially being due to pubertal Tanner stage. To address these biological
 confounds, age will be stratified for in equal numbers during recruitment (10-14 years and
 15-19 years) and pubertal Tanner stage will be controlled for in analyses. Finally, youth
 participants may refuse blood draw, weight/height measurement, or blood pressure measurement.
 However, these are standard medical procedures that this pediatric patient population is very
 familiar with by 10 years of age. Our clinic routinely uses ultrasound guided blood draws to
 reduce the number of needle sticks needed to obtain adequate blood sample. Additionally,
 every effort to use lidocaine numbing cream and distraction during blood draws will be made
 for youth who express anxiety regarding venipuncture blood draw.

 Statistical Analyses Power and Sample Size: Statistical analyses will be conducted with the
 MCCTR Biostatistical Core (Seth Lirette, PhD). G*Power 3.0.10 chi-squared a-priori power
 analyses specified that a sample size of 100 youth (50 per weight-status group) will provide
 greater than 90% power for detecting differences in the prevalence rate of relative
 hypertension (primary outcome) in youth with SCD who are overweight/obese versus youth with
 SCD who are underweight/normal weight. An anticipated large effect size (.8) for power
 analyses is based on the prevalence rate of 4.5% for hypertension in African American youth
 10-19 years who were obese compared to a prevalence rate of 40.2% for relative hypertension
 in African American young adults 18-20 years with SCD.

 Attrition and Missing Data: The investigators anticipate a small portion (approximately 5%)
 of unusable laboratory data due to clinical difficulties with blood draw (e.g., nurse not
 able to draw enough blood). Based on the above power analyses, the total target sample of
 N=100 youth will provide a large enough sample size to account for this type of random
 missing laboratory data. Questionnaires will be checked by the study nurse coordinator for
 completeness prior to study completion. Random missing questionnaire data will be handled or
 imputed using author recommendations or mean imputation strategies.

 Analytic plan Aim 1: Statistical analyses will be calculated in SPSS 26.0 or Stata 15.0.
 Prevalence rates of hypertension, hyperlipidemia and hyperglycemia will be calculated for the
 two study groups. A series of non-parametric exact Fisher tests will examine the prevalence
 rate of hypertension, hyperlipidemia and hyperglycemia in pediatric patients with SCD who are
 overweight or obese (i.e., have a BMI ≥ 85th percentile) compared to their underweight and
 normal weight (i.e., have a BMI 1st to 84th percentile) counterparts, controlling for Tanner
 pubertal stage.

 Analytic plan Aim 2: A series of logistic regressions will examine the differential impact
 (odds ratio) of diet, exercise, and family history of overweight/obesity on the risk for
 weight status, hypertension, hyperlipidemia, and hyperglycemia in youth with SCD, controlling
 for Tanner pubertal stage.
Inclusion Criteria:

 -  10-19 years

 -  diagnosed with SCD genotype HbSS, HbSβ0, HbSC, or HbSβ+

 -  regularly followed by the UMMC Pediatric SCD clinic (i.e., average visit at least once
 per year in past two years)

 Exclusion Criteria:

 -  non-English speaking

 -  patient in acute vaso-occlusive pain crisis (which can increase blood pressure)

 -  cognitive or developmental delays that preclude ability to complete study
 questionnaires