Exercise capacity and clinical outcomes in adults followed in the Cooperative Study of Sickle Cell Disease (CSSCD)

Exercise and training in sickle cell disease: Safety, potential benefits, and recommendations

Sickle cell disease (SCD) is a genetic disorder characterized by complex pathophysiological mechanisms leading to vaso-occlusive crisis, chronic pain, chronic hemolytic anemia, and vascular complications, which require considerations for exercise and physical activity. This review aims to elucidate the safety, potential benefits, and recommendations regarding exercise and training in individuals with SCD. SCD patients are characterized by decreased exercise capacity and tolerance. Acute intense exercise may be accompanied by biological changes (acidosis, increased oxidative stress, and dehydration) that could increase the risk of red blood cell sickling and acute clinical complications. However, recent findings suggest that controlled exercise training is safe and well tolerated by SCD patients and could confer benefits in disease management. Regular endurance exercises of submaximal intensity or exercise interventions incorporating resistance training have been shown to improve cardiorespiratory and muscle function in SCD, which may improve quality of life. Recommendations for exercise prescription in SCD should be based on accurate clinical and functional evaluations, taking into account disease phenotype and cardiorespiratory status at rest and in response to exercise. Exercise programs should include gradual progression, incorporating adequate warm-up, cool-down, and hydration strategies. Exercise training represents promising therapeutic strategy in the management of SCD. It is now time to move through the investigation of long-term biological, physiological, and clinical effects of regular physical activity in SCD patients.

Prevalence and Risk Factors of Stroke Among Children With Sickle Cell Disease: A Retrospective Study at a Tertiary Care Center

Background Sickle cell disease (SCD) is a common autosomal recessive inherited hemoglobin disorder in many countries. Neurological complications are among the most disabling complications in SCD. Stroke and cerebral vasculopathy can lead to further neurological insult. Ischemic insults, stroke, and silent infarcts are preventable causes of morbidity and mortality in SCD patients. Understanding the epidemiology and characteristics of such patients will help to prevent complications.  Methodology This is a retrospective study conducted in a tertiary care center in Saudi Arabia. Cases of SCD admitted to the pediatric ward between the years 2019 to 2023 were included in the study. Demographic data, clinical diagnosis, and frequency of prior admissions were collected. Brain imaging results were reviewed and included. Furthermore, the study assessed common risk factors leading to developing a stroke in SCD pediatric patients. Risk factors and clinical outcomes after stroke were also included. Results Eighty-one patients were enrolled. The mean age of stroke patients was 8.21±3.50 years while the mean age of non-stroke patients was 6.24±3.76 years. More than half of the patients were females in both the stroke (61.50%) and non-stroke groups (52.90%). Thirteen SCD patients (16%) were diagnosed with stroke. Previous history of stroke, high mean corpuscular volume (MCV), and low red blood cells count (RBC) were statistically significant risk factors for stroke (p<0.0001), (p<0.0001), (p<0.03), respectively.  Conclusion Stroke is one of the most devastating complications of SCD. The prevalence of stroke among SCD patients in our study was 16%. Transcranial Doppler ultrasound screening is the most important predictor of stroke.

Motivators and Barriers to Physical Activity among Youth with Sickle Cell Disease: Brief Review

Purpose: Health disparities for minority groups include a low rate of physical activity and underserved urban minority youth with chronic disease are among the least active population segments, as exemplified by sickle cell disease (SCD). “Exercise prescriptions” for youth with chronic diseases need to be evidence based and align with psychologic motivators and barriers. This scoping review sought evidence for psychosocial motivators or barriers to physical activity (PA) in youth with SCD and other chronic disease that could be relevant to SCD. Methods: Five databases were searched for studies on urban minority youth published between 2009 and 2022. Results: Keyword searching yielded no papers on SCD and PA motivation and barriers. Adding health-related quality of life (HRQL) in SCD found eleven relevant papers. Widening the search to chronic disease in minority youth resulted in a total of 49 papers. Three thematic categories and seven sub-themes emerged. PA barriers added by chronic disease include fear of triggering disease complications, negative relationships due to disease limitations on performance in sports, and lack of suitable environment for PA that accommodates the chronic disease. PA motivators are similar for youth without chronic disease: self-efficacy, autonomy, positive relationships with peers and parents and coach/teacher. Conclusion: Direct descriptions of PA motivations and barriers to PA in SCD are limited to fatigue and fear of sickle vaso-occlusive pain. The PA barriers and motivators found for urban youth with chronic disease overlap with themes in healthy adolescents from underserved minorities. Community-based interventions could strengthen PA motivators (self-efficacy, autonomy, positive relationships with peers and parents and coach/teacher) but need disease accommodations to overcome the barriers (fear of triggering disease complications, environmental limitations, and negative relationships). Evidence-based exercise prescriptions might incorporate educational modules to overcome disease stigma and misconceptions. Prospective studies of PA motivators and barriers could improve HRQL in SCD.

The Sickle Cell Disease Functional Assessment (SCD-FA) tool: a feasibility pilot study

Background

The life expectancy for individuals with sickle cell disease (SCD) has greatly increased over the last 50 years. Adults with SCD experience multiple complications such as cardiopulmonary disease, strokes, and avascular necrosis that lead to limitations that geriatric populations often experience. There are no dedicated instruments to measure functional decline and functional age to determine risk of future adverse outcomes in older adults with SCD. The objective of this study was to assess the feasibility of performing the Sickle Cell Disease Functional Assessment (SCD-FA).

Methods

We enrolled 40 adults with SCD (20 younger adults aged 18–49 years as a comparison group and 20 older adults aged 50 years and older) in a single-center prospective cohort study. Participants were recruited from a comprehensive sickle cell clinic in an academic center in the southeastern United States. We included measures validated in an oncology geriatric assessment enriched with additional physical performance measures: usual gait speed, seated grip strength, Timed Up and Go, six-minute walk test, and 30-second chair stand. We also included an additional cognitive measure, which was the Montreal Cognitive Assessment, and additional patient-reported measures at the intersection of sickle cell disease and geriatrics. The primary outcome was the proportion completing the assessment. Secondary outcomes were the proportion consenting, duration of the assessment, acceptability, and adverse events.

Results

Eighty percent (44/55) of individuals approached consented, 91% (40/44) completed the SCD-FA in its entirety, and the median duration was 89 min (IQR 80–98). There were no identified adverse events. On the acceptability survey, 95% (38/40) reported the length as appropriate, 2.5% (1/40) reported a question as upsetting, and 5% (2/40) reported portions as difficult. Exploratory analyses of physical function showed 63% (25/40) had a slow usual gait speed (< 1.2 m/s).

Conclusion

The SCD-FA is feasible, acceptable, and safe and physical performance tests identified functional impairments in adults with SCD. These findings will inform the next phase of the study where we will assess the validity of the SCD-FA to predict patient-important outcomes in a larger sample of adults with SCD.

Physical Impairment and Function in Children and Adolescents With Sickle Cell Disease: A Systematic Review

OBJECTIVE

To examine physical impairments and physical function in children and adolescents with sickle cell disease (SCD).

DATA SOURCES

PubMed, Embase (embase.com), Cumulative Index to Nursing and Allied Health (EBSCO), Cochrane Central Register of Controlled Trials (Wiley), and Dissertations and Theses (ProQuest) were searched from January 1, 1990, to September 25, 2020. References retrieved were required to include a term for SCD and a term for physical impairments or physical function. Results were limited to articles with children and adolescents and in the English language.

STUDY SELECTION

A total of 3054 nonduplicate articles were independently screened by 2 reviewers, resulting in 240 articles for full-text review. The full-text review, performed by 2 independent reviewers, resulted in 67 articles.

DATA EXTRACTION

Data were extracted from each full text to a custom Excel document by a single reviewer and were verified by a secondary reviewer.

DATA SYNTHESIS

The studies identified in this systematic review offer evidence that children and adolescents with SCD demonstrate physical impairments and physical function limitations compared with control participants as noted by varying percentages in deficits up to 19%-58% in muscle and bone composition and/or symptoms, muscle strength, cardiopulmonary function, motor performance, physical activity, and physical function domains of quality of life questionnaires.

CONCLUSIONS

Children and adolescents with SCD present with physical impairments and physical function limitations. Scientists and clinicians should consider developing collaborative standards to define and objectively measure physical impairment and function in this population to comprehensively examine the underlying factors that contribute to physical impairments and function.

Safety of maximal cardiopulmonary exercise testing in individuals with sickle cell disease: a systematic review

OBJECTIVE

We evaluated the safety of maximal cardiopulmonary exercise testing (CPET) in individuals with sickle cell disease (SCD). Maximal CPET using gas exchange analysis is the gold standard for measuring cardiopulmonary fitness in the laboratory, yet its safety in the SCD population is unclear.

DESIGN

Systematic review.

DATA SOURCES

Systematic search of Medline (PubMed), EMBASE, Cochrane, ClinicalTrials.gov and professional society websites for all published studies and abstracts through December 2020.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Two reviewers independently extracted data of interest from studies that assessed safety outcomes of maximal CPET in children and adults with SCD. A modified version of the Newcastle-Ottawa Scale was used to assess for risk of bias in studies included.

RESULTS

In total, 24 studies met inclusion/exclusion criteria. Adverse events were reported separately or as part of study results in 36 (3.8%) of 939 participants with SCD undergoing maximal CPET in studies included. Most adverse events were related to transient ischaemic changes on ECG monitoring or oxygen desaturation during testing, which did not result in arrhythmias or other complications. Only 4 (0.43%) of 939 participants experienced pain events due to maximal CPET.

CONCLUSION

Maximal CPET appears to be a safe testing modality in children and adults with SCD and can be used to better understand the physiological basis of reduced exercise capacity and guide exercise prescription in this population. Some studies did not focus on reporting adverse events related to exercise testing or failed to mention safety monitoring, which contributed to risk of bias.

Cardiovascular benefits of a home-based exercise program in patients with sickle cell disease

BACKGROUND

Physical inactivity is an important risk factor for cardiovascular disease. The benefits of exercise in patients with chronic diseases, including cardiovascular diseases, are well established. For patients with sickle cell disease, medical recommendation was to avoid physical exercise for fear of triggering painful crises or increasing the impairment of the cardiopulmonary function. Only recently, studies have shown safety in exercise programs for this population. Despite that, there is no report that assess the effects of physical exercise on cardiac parameters in patients with sickle cell disease.

OBJECTIVE

This study aimed to evaluate the impact of regular physical exercise (a home-based program) on cardiovascular function in patients with sickle cell disease.

DESIGN

A quasi-randomized prospective controlled trial.

SETTING

During the years 2015 and 2016, we started recruiting among adult patients treated at a Brazilian Center for Patients with Sickle Cell Disease to participate in a study involving a home exercise program. The experimental (exercise) and control groups were submitted to clinical evaluation and cardiovascular tests before and after the intervention. Analysis of variance was applied to compare groups, considering time and group factors.

PARTICIPANTS

Twenty-seven adult outpatients with a sickle cell disease diagnosis.

INTERVENTIONS

Exercise group (N = 14): a regular home-based aerobic exercise program, three to five times per week not exceeding give times per week, for eight weeks; no prescription for the control group (N = 13).

MAIN OUTCOME MEASURES

Echocardiographic and treadmill test parameters.

RESULTS

The exercise group showed significant improvement in cardiovascular tests, demonstrated by increased distance traveled on a treadmill (p<0.01), increased ejection fraction (p < 0.01) and improvement of diastolic function assessed by mitral tissue Doppler E' wave on echocardiography (p = 0.04). None of the patients presented a sickle cell crisis or worsening of symptoms during the exercise program.

CONCLUSION

The selected home-based exercise program is safe, feasible, and promotes a favorable impact on functional capacity and cardiovascular function in sickle cell disease patients.

The Effects of Hydroxyurea Therapy on the Six-Minute Walk Distance in Patients with Adult Sickle Cell Anemia: An Echocardiographic Study

Background

The impact of hydroxyurea (HU) medication as treatment of choice has not been evaluated in adult sickle cell anemia (SCA) patients in terms of the 6-min walk distance (6 MWD).

Aim

The aim of the study was evaluating the effects of HU on the 6 MWD, serum brain natriuretic peptide (NT-pro BNP) level, and pulmonary hypertension (PH) measured by tricuspid regurgitation velocity (TRV).

Methods

In this cross-sectional, prospective study, 110 patients with homozygous SCA were studied and compared with age- and gender-matched healthy controls. Every patient was investigated via pulsed and tissue Doppler echo evaluation, 6-min walk test (6 MWT), and blood level for the level of NT-pro-BNP hormone. Data were compared in patients with (n = 59; group 1, G1) and without (n = 51; group 2, G2) HU medication. Pearson correlation analysis was applied and clinical follow-up for the frequency of acute chest syndrome (ACS). Analysis of variance (ANOVA) multivariate statistical analysis was applied between groups.

Results

In the study, 110 patients with SCA were studied and compared with 110 control patients. Patients in G1 compared with G2 had a longer 6 MWD (491 ± 64.4 m vs 428.6 ± 54.3 m, p < 0.005), higher HbF% (21 ± 2.5% vs 8 ± 1.8%, p < 0.005), and lower NT-pro-BNP level (314.1 ± 27.5 pmol/L vs 407 ± 18.9 pmol/L, p = 0.05). The mean TRV values were 2.8 ± 0.5 m/s in G1 versus 3.4 ± 0.4 m/s in G2, p < 0.005, and 1.5 ± 0.7 m/s in the control group. The high probability of PH based on a TRV > 3.4 m/s was 10.1% in G1 versus 17.6% in G2 and 3.6% in the control. There were weak positive correlations between NT-pro-BNP and TRV (r = 0.264; p = 0.005) and HbF% and 6 MWD (r = 0.452; p = 0.001). After 12 months of follow-up, frequency of acute chest syndrome (ACS) was twice as high in G2, at 32 patients, versus 16 in G1.

Conclusion

Patients with SCA on HU medication compared with no HU had significantly longer 6 MWD, lower level of NT-pro-BNP, higher HbF% level. After 1-year follow-up HU patients had less frequency of ACS. There were significant positive correlations between the level of NT-pro BNP level and TRV in m/s on echo.

Physical Activity and Pain in Youth With Sickle Cell Disease

Study objectives were to examine the relationships between physical activity, pain, and psychological distress in youth 8 to 17 years of age with sickle cell disease. Participants were 206 youth with sickle cell disease (M = 11.73 years, 54.9% female, 99.5% African American). Caregivers and youth completed a clinical psychosocial screening battery. Results revealed frequent pain (37.6%), moderate median pain intensity, and elevated median pain interference in youth. Lower caregiver-reported physical activity was associated with worse pain outcomes. Increased anxiety was also associated with worse pain outcomes. A better understanding of the relationship between physical activity/inactivity and pain will guide multifactorial treatment interventions.

Blood Rheology: Key Parameters, Impact on Blood Flow, Role in Sickle Cell Disease and Effects of Exercise

Blood viscosity is an important determinant of local flow characteristics, which exhibits shear thinning behavior: it decreases exponentially with increasing shear rates. Both hematocrit and plasma viscosity influence blood viscosity. The shear thinning property of blood is mainly attributed to red blood cell (RBC) rheological properties. RBC aggregation occurs at low shear rates, and increases blood viscosity and depends on both cellular (RBC aggregability) and plasma factors. Blood flow in the microcirculation is highly dependent on the ability of RBC to deform, but RBC deformability also affects blood flow in the macrocirculation since a loss of deformability causes a rise in blood viscosity. Indeed, any changes in one or several of these parameters may affect blood viscosity differently. Poiseuille's Law predicts that any increase in blood viscosity should cause a rise in vascular resistance. However, blood viscosity, through its effects on wall shear stress, is a key modulator of nitric oxide (NO) production by the endothelial NO-synthase. Indeed, any increase in blood viscosity should promote vasodilation. This is the case in healthy individuals when vascular function is intact and able to adapt to blood rheological strains. However, in sickle cell disease (SCD) vascular function is impaired. In this context, any increase in blood viscosity can promote vaso-occlusive like events. We previously showed that sickle cell patients with high blood viscosity usually have more frequent vaso-occlusive crises than those with low blood viscosity. However, while the deformability of RBC decreases during acute vaso-occlusive events in SCD, patients with the highest RBC deformability at steady-state have a higher risk of developing frequent painful vaso-occlusive crises. This paradox seems to be due to the fact that in SCD RBC with the highest deformability are also the most adherent, which would trigger vaso-occlusion. While acute, intense exercise may increase blood viscosity in healthy individuals, recent works conducted in sickle cell patients have shown that light cycling exercise did not cause dramatic changes in blood rheology. Moreover, regular physical exercise has been shown to decrease blood viscosity in sickle cell mice, which could be beneficial for adequate blood flow and tissue perfusion.