The purpose of this study is to use comprehensive exercise testing to examine longitudinal changes in exercise capacity over a 2 year period in children and young adults with sickle cell anemia.

Although the burden of sickle cell anemia (SCA) on affected individuals is significant, few studies have examined the influence of having SCA on such measures of physical function as exercise capacity. Moreover, the physiologic basis of poor physical functioning in children with SCA is unknown and has not been studied extensively. The purpose of this proposal is to use cardiopulmonary exercise testing (CPET) to gain a comprehensive understanding of longitudinal changes in exercise capacity, and the effect of poor exercise capacity on quality of life in children and young adults with SCA. The specific aims of this project are to: 1) Measure peak oxygen consumption (VO2), the reference standard for exercise capacity, in children and young adults with SCA classified by primary pathophysiologic contributor to their decreased exercise capacity, and 2) compare results of this exercise test with the results of previously completed exercise tests to determine longitudinal changes in exercise capacity. These aims will be performed in 60 subjects with SCA and 30 matched controls who participated in a previous study, IRB# 2009-13659; "The Physiologic Assessment of Exercise Capacity in Pediatric Sickle Cell Anemia". In a secondary analysis, we will also study the participants quality of life using a set of validated questionnaires. This study is essential because it will address several areas of exercise capacity, including the longterm effects of physiologic contributors to exercise limitation, that remain fundamental knowledge gaps in SCA.

Inclusion Criteria:

1. age 8 to 21 years old; AND
2. Hb SS or S-β0 thalassemia disease, confirmed by hemoglobin analysis; AND
3. Previously participated in ClinicalTrials.gov ID: NCT01527799

Exclusion Criteria:

1. inability to perform maximal testing due to physical limitation (e.g. stroke or avascular necrosis); OR
2. history of exercise-induced syncope or arrhythmias. Subjects will wait at least 2 weeks following any vaso-occlusive pain episode and 12 weeks following any disease-related complication requiring transfusion support. Individuals on hydroxyurea will be eligible. A total of 30 controls without SCA or sickle cell trait will be matched for age, sex and race and recruited from the siblings, friends or relatives of subjects enrolled on this study

Sickle cell anemia patients followed at Children's Memorial Hospital. Healthy controls without sickle cell anemia or sickle cell trait are recruited through flyers posted in Children's Memorial Hospital.