Sickle Cell Disease Management: The Role of SLPs and Audiologists, Part 2

Editor’s Note: This text is a transcript of the course, Sickle Cell Disease Management: The Role of SLPs and Audiologists, Part 2, presented by Candice J. Adams-Mitchell, SLP.D, CCC-SLP.

Learning Outcomes

After this course, participants will be able to:

• Identify the barriers to individuals with SCD receiving speech pathology and audiology services.
• Describe the speech-language pathologist’s and audiologist's role in treating individuals with SCD.
• Describe the current research related to hearing, cognition, and language in individuals with SCD.

Review of Sickle Cell Disease (SCD) and the Common Complications

What is Sickle Cell Disease?

I want to review some of the content that was discussed in Part 1.   Sickle cell disease is a group of inherited red blood cell disorders that affects millions of people throughout the world. According to the Centers for Disease Control and Prevention, it is estimated that about 100,000 people in the United States suffer from sickle cell disease, with mainly Black Americans or African Americans being affected.

A person with sickle cell disease has that one different substance, the amino acid valine, that impacts how their body makes up hemoglobin.  That chemical causes their body to form long strings when it gets rid of its oxygen and causes the red blood cell to form into a sickle shape.

Sickle cell disease is associated with an increased risk of early death and adverse clinical complications that impact various organ systems. And in turn, those patients and their family members report significantly diminished quality of life.

Again, sickle cell disease causes these individuals to have a difference in how their red blood cells are made. In a normal red blood cell, these blood cells live for 120 days. They have a biconcave disc shape and are not deformable, meaning they stay in that shape unless an individual has another red blood cell disorder or a hemoglobin disorder.  With sickle cell disease, the blood cells are rigid, inflexible, and sickle shape. Because they are deformed, they cannot move through the blood vessels. That blockage results in the inability to provide oxygen to tissues in the body. Lack of tissue oxygenation causes excruciating pain, damage to body organs, and even death.

Anemia is another common complication because the red blood cells die at about 20 days instead of the normal 120 days. There are musculoskeletal issues, especially pain, because individuals are not getting enough oxygen to their tissues and other organs. They experience growth retardation and atypical skeletal development. The central nervous system is impacted because individuals are prone to having strokes due to the sickled cells trying to move through small vessels. Acute chest syndrome, liver issues, and acute splenic sequestration occur. Dactylitis, swelling of the hands and feet, also occurs, which is extremely painful.   

There are complications with the genitourinary system, asthma, vision, jaundice, immunological, and respiratory issues. Individuals with sickle cell disease are prone to many infections because their spleen is not functioning. Aplastic crises can occur when the body stops the production of red blood cells, which then requires a blood transfusion.

Barriers to Patients with SCD Receiving Speech and Audiological Therapy

After reviewing all of those complications, you may wonder why you don't ever see these patients on your caseload. There are some definite barriers.  So, I compiled a list of what patients and their families have said when I've spoken with them, and I looked at it from different perspectives. 

Patient Level

From a patient level, one of the barriers is a lack of knowledge about our services. They don't know what we do. They don't know the services that we provide, whether it's in a medical setting or a school setting. Some of the same barriers that exist for why other people don't seek out our services exist for individuals with sickle cell disease as well.  

Additionally, individuals who do know about our services don't know if those services are available in their community. Access is a huge barrier. Some individuals can't get to us because we're unavailable in some of their communities.  And, being honest, when you think about individuals who are primarily impacted by sickle cell disease - Blacks, African Americans - traditionally, we're seeing those individuals in lower SES environments, where audiology and speech pathology services are not readily available. So, we have to be more intentional about seeking them out because they may not be able to get to us.

Another barrier is the availability of family members to take them to additional doctor's appointments. These patients are potentially already being seen by many providers, such as hematology, neurology, GI, pulmonary, and ophthalmology. Depending on how severe their complications are due to sickle cell disease and other comorbidities, they might rely on family members to provide transportation to these doctor's appointments. It can be very hard for them to tack on one more thing, and sometimes speech-language pathology and audiology is that one more thing. They don't have a choice to see providers who are helping with the physical aspects of the disease.  They will go to their hematology appointments because they need their pain medications. They're going to make their GI appointments, etc. Sometimes our services fall on the back burner because we aren't necessarily keeping them alive; it's more of a quality-of-life issue. So, when they have to ask someone to take them to a provider's appointment, they will likely prioritize them. Sometimes, speech pathology and audiology are the appointments that are pushed aside even if they know what we do and have a referral to us.

There's also a financial barrier. Uninsured or managed care insurance does not pay for SLP and audiology services. It's not because they don't see the justification. There's a lot of research for sickle cell disease regarding bones, movement, hip replacements, et cetera. Sickle cell patients might be on a physical therapist's caseload because insurance companies don't balk at that. But, it's not uncommon for insurance companies to not reimburse our services.

The last barrier at the patient level is the added stigma and stereotypes that are associated with sickle cell disease, "You're pain seeking," "You're always in the hospital," and "You're always sick." Patients don't want any more labels than what they already have. So those are the barriers from a patient's perspective.

Parent/Family/Caregiver Level

The family members or the caregivers don't know about what we do, whether it's in schools or in hospitals. It's up to us to educate family members on how we might be of service to them. They also don't have knowledge about the speech-language and hearing behaviors that can be impacted by sickle cell disease.  Even if they know what we do, they may not be thinking about speech, language, hearing, cognition, or swallowing. They don't know how sickle cell disease impacts those areas.

Lastly, from a family and caregiver level, when a patient has someone speaking for them during their appointments, that individual may not have the whole picture of the patient and all of their complications.  The person who is providing the report may not be painting a holistic picture of their speech and language and cognitive issues that they're noticing at home. They are most likely reporting what's going on at that moment.  While we appreciate the parents, the families, and the caregivers who are providing the services for them, the barrier is that they deal with the here and now when they're bringing them to doctor's appointments or when we see them in the schools. They don't necessarily have the best picture of how this disease truly impacts these patients.

Provider Level

Another barrier can be the provider. There is a lack of knowledge about our services on the provider's part. The hematologist, oftentimes, does not know everything that speech-language pathologists or audiologists do.  And that's okay.  Again, it's our job to provide that education.

But, consistently across the board, patients, their families, and providers don't necessarily think about what we do and how we can improve the quality of life for these patients.

There is provider bias and negative attitudes towards sickle cell disease patients and their treatments. Much of the literature focuses on pain for these individuals. Still, a lot of the literature also focuses on the negative stereotypes associated with patients who have sickle cell disease. They are often deemed as drug-seeking patients because of the high level of pain medications they're on. Because they generally know what dose of medication works for them (e.g., "I need this amount of morphine.") oftentimes, they're looked at as a drug seeker. But in reality, they're very knowledgeable about their disease.  Unfortunately, the providers of these patients are the main ones who have characterized them as drug seekers and patients who are "frequent flyers" in the hospital for whatever reason. They are not considering that these individuals don't want to be in the hospital because of how they are treated. So the negative attitudes and the bias are barriers for them.

Another barrier is the limited experience of physicians caring for patients who have sickle cell disease. Many physicians, even hematologists, have very limited experience in caring for these patients and what they need unless they specialize in sickle cell disease. Because they don't know much about sickle cell disease and the complications of the disease, they most likely won't know that patients will benefit from an SLP or audiology consult.

Additionally, at the provider level, physicians aren't engaging these patients and their caregivers in their treatment plans. If they did, those individuals with speech, language, and/or audiology needs would say they need to be followed by an SLP or an audiologist for whatever they are experiencing.

As I have mentioned before, physicians typically focus on treating the most acute complications at the time of the visit because this disease can cause very acute life-threatening complications. When patients come into the hospital, while they might be experiencing difficulty with swallowing or altered mental status, if that results from acute chest syndrome, splenic sequestration, or more life-threatening things, that is where the physician will focus his/her attention.  They focus on acute complications all the time when they are seeing these patients and not complications like an altered mental status or a child who is struggling in school. Those are generally not the issues being brought up in these appointments.

Systems Level

From a systems level, one barrier would be is financing. Individuals with sickle cell disease don't have the type of insurance that will pay for additional speech pathology and audiology services.  Therefore, they might have to pay out of pocket.

The geographic isolation of SLPs and audiologists is another barrier at the systems level. SLPs aren't everywhere, and some of these individuals live in rural areas where they're already traveling an hour or two hours to their doctors' appointments. So there is limited access to our services. We aren't there to recruit and retain clinicians who are competent in providing comprehensive care to patients who have sickle cell disease.

There's also a lack of coordination between hospitals and community-based clinicians. Individuals might be seen by audiology or followed by speech pathology while they're in the hospital. Then when they leave, both children and adults are not being followed by community-based clinicians. Parents and caregivers don't follow up with seeing a private therapist or school therapist.  They're being seen on the medical side, but when they leave, there's no coordination to say they need to continue those services.

There is limited access to comprehensive care centers and comprehensive care models, which we know would be more beneficial for these patients because of the number of medical professionals they see.

The last barrier at the systems level is transitioning from pediatric to adult care. Everybody loves working with children. They are followed and parents bring them to their appointments.  If they need speech therapy, the parents are generally the ones who are going to say, "Hey, they've got some delayed speech," or "They have some hearing issues." But, the transition to adult care has shown that a lot of that follow-through and reporting of additional needs and services start to decline. 

What Does the Research Say

Now that you're armed with the knowledge of why you haven't seen these patients on your caseload, I want to discuss what the research says about sickle cell disease and our role in caring for these patients. There's not a lot of literature regarding speech-language pathology and audiology and what we could be doing for these patients. The research that is available is dated but worth discussing. 

Hearing-related Concerns in Individuals with SCD

These include sensorineural hearing loss, hidden hearing loss, ototoxic medications, and recurrent respiratory infections that could result in otitis media.  We know how important good hearing acuity is for developing speech and language. When there is a vaso-occlusions, and the sickle cells become occluded in the vessels, that can cause hearing loss.  It is believed that this occurs due to that obstruction in the capillary bed of the stria vascularis in the inner ear. During vaso-occlusions or crises, those sickle cells occlude the small veins that are in the stria vascularis and can impact a child's ability to hear. 

Sensorineural and Conductive Hearing Loss in Individuals with SCD

As early as 1969, Morganstein and Menace found that sensorineural hearing loss has been reported during sickle cell crises. They noticed that the sickle blood cells were clumping in the veins and the capillaries of the temporal bone. Then in 2018, Lagos and his colleagues piggybacked off of that study and investigated the prevalence of sensorineural hearing loss in children and adolescents with sickle cell anemia and its association with endothelial dysfunction (ED). Their study identified a significant association between ED and sensorineural hearing loss.

Other studies have shown that between 3-22% of patients who have sickle cell anemia have sensorineural hearing loss greater than 25 dB. In addition, there is evidence that suggests children with sickle cell, whose first vaso-occlusion crisis occurs during their first year, 58.3% exhibited hearing loss later on that affected frequencies from 500Hz to 4,000Hz. So the reported cases of hearing loss that occurred in patients have been those who have sickle cell anemia or one of those thalassemias.

Also, it's important to note that because of spleen dysfunction, these individuals are prone to multiple respiratory infections, which can cause ear infections.  Permanent hearing loss from otitis media is, therefore, very present in this population.

Hearing Loss in Individuals with SCD (Hidden Hearing Loss)

A relatively new research interest is hidden hearing loss in patients with sickle cell disease. However, patients have been complaining about it for years. It is the idea that children and adults with sickle cell disease may have a higher rate of sensorineural and central auditory hearing impairment with normal hearing thresholds. 

In 2020, King conducted a case study to examine hidden hearing loss in an African American boy who had sickle cell disease and presented with normal hearing thresholds. In that same year, Rissatto and his colleagues also studied hidden hearing loss in patients with sickle cell disease. They discovered damage in the auditory system in these patients that can be present involving the retrocochlear structures, causing functional deficits and what the patient perceives as hearing loss.

Commonly Used Ototoxic Medications Used to Treat SCD

As previously mentioned in Part 1, there are two treatments for sickle cell disease. There are blood transfusions to prevent strokes and hydroxyurea medication, which boosts fetal hemoglobin to prevent the blood cells from sickling. However, that is an ototoxic medication that can cause hearing loss.

Some patients who have chronic anemia are on chronic blood transfusions. That places these patients at risk of having iron overload, which can lead to significant medical complications because the body will store that iron in the liver.  To remove that excess liver iron, they are given Desferal (also called Jadenu). However, when given over a long period, it impacts vision and can cause hearing loss.

Hydroxyurea is a chemotherapy-class drug that patients with sickle cell disease may take if they receive bone marrow transplants. In the same way that other chemotherapy drugs can impact hearing, Hydroxyurea can have the same effect on these patients.  

Language Impairment in Children with Sickle Cell Disease

The literature on language impairment in children with sickle cell disease dates back to 1937. At that time, Bosselman and Kraines saw a 13-year-old male with aphasia-like symptoms following a cerebrovascular acid accident. His responses looked much like individuals with aphasia from any stroke: the difficulty naming objects, reduced auditory comprehension, literal and verbal paraphasias, impaired reading, the disorientation, all of those symptoms that are very similar to other patients who have CVAs.  In patients with sickle cell disease, because they have silent cerebral infarcts happening so much, while they have not had a large-scale stroke, their language can often mirror someone who has had one.

Continuing to look at language impairment in children with sickle cell disease, Gillum, in 1977, looked at receptive and expressive language skills of 20 children with sickle cell disease between the ages of three and nine over a four-year period. Results of that study showed that language disruption happens in children with sickle cell disease compared to same-age peers. Similar results were found by other researchers when they studied the cognitive functions of a child after a CVA.

When children start to have sickle cell crises and are absent from school, they will have difficulties with language skills because they are experiencing periods of language disruption. But for the most part, these children track alongside their peers. 

Articulation Disorders in Children with Sickle Cell Disease

In 1997, Betholyn Gentry did a lot of work in our field regarding sickle cell disease. She tested 50 children aged 3 to 21 years who had sickle cell disease using the Fluharty Language Screening Test, the Joliet 3-Minute Speech and Language Screen, and had them read the "Grandfather" passage. Ten percent of those children failed the speech screening by exhibiting evidence of articulation and fluency disorders. Although that's not a large percentage, no research has been conducted in this area since that study. 

Reading Skills in Children with Sickle Cell Disease

Reading skills of children with sickle cell disease have also been studied by Betholyn Gentry. Specifically, she examined reading and writing of eight children with sickle cell disease who suffered from stroke. Children ranging from grades 2 through 11 were tested as they participated in their transfusion therapy. They were matched with eight normal peers. Results of the study indicated that the mean standard scores for those children with sickle cell disease who had a stroke years prior were consistently below those of the control group. That was true for reading recognition, reading comprehension, and overall total reading scores. 

Writing Skills in Children with Sickle Cell Disease

Another area of concern is writing skills in children with sickle cell disease. The pattern that was found in the children's reading skills was also seen in writing skills in that same study. Three of the eight children in this study failed all four writing subtests, and one failed three of the subtests in which they were provided. Their writing is particularly delayed with errors such as incomplete sentences, run-on sentences, lack of correct punctuation, capitalization, and incorrect verb tense usage.

Cognitive Deficits and Education Attainment in Children with Sickle Cell Disease

We've touched on the cognitive deficits that might be seen in these individuals. Still, Schatz, in 2018, has done a lot of work with sickle cell and cognition, evaluating educational attainment and neuropsychological deficits in children with sickle cell disease. How are they tracking with their peers from a school standpoint, especially those who were constantly having silent cerebral infarcts? What they noticed in this study was children with silent cerebral infarcts had twice the rate of school difficulties as children without infarcts, which is what you would expect. Eighty percent of silent infarct cases had clinically significant cognitive deficits, whereas 35% had deficits in academic skills.

Additionally, children with silent cerebral infarcts show high rates of poor educational attainment (i.e., how they track through school, how they move and matriculate through school), cognitive deficits, and frontal lobe injury. Poor school performance and sickle cell disease are considered to be an indicator of a child having silent cerebral infarcts.  So, if you're working in a school setting, be mindful that poor performance in school may indicate the child is having silent cerebral infarcts.

Feeding and Swallowing in Children with Sickle Cell Disease

Cerebrovascular accidents in children with sickle cell disease can result in undiagnosed dysphasia. Respiratory swallow coordination due to lung disease and the respiratory issues they have, such as chronic asthma, can be an issue for these patients. It's also documented that severe anemia and fatigue contribute to weight loss and dehydration in both children and adults who have sickle cell disease.

Schatz conducted a study in 2018 on developmental screenings and assessments, which are typically indicative of social and environmental risk factors.  He administered developmental screenings and assessments to three-year-olds who had sickle cell disease.  This was actually a longitudinal study to assess whether developmental concerns for toddlers would predict subsequent academic outcomes in patients who have sickle cell disease. The study also evaluated whether developmental screenings could help predict academic outcomes differently for toddlers compared to older children. Ninety families participated in developmental screening programs at their local sickle cell specialty clinic. Patient questionnaires and medical record data were collected from a cohort that received developmental screenings between September 2004 and May 2008 as toddlers or early school age.

The study's results confirmed that toddlers and school-aged children with sickle cell disease who had abnormal language and cognitive screenings had significantly elevated risk for future academic challenges. In addition, those same children had elevated risks for abnormal transcranial Dopplers when looking at their risk for stroke. This demonstrates the value of completing developmental and cognitive screenings in this high-risk population. Those screening results can be extremely helpful in implementing a more thorough screening program and a more aggressive referral program for early intervention services for speech, audiology, occupational therapy, and academic support. Ultimately, this should shift providers' perspectives to consider that sickle cell disease is not just a pain disorder but also a developmental disorder.

COVID-19 and Sickle Cell Disease

In these last few years, another thing that has impacted sickle cell care is COVID-19. As we have discussed, people with sickle cell disease are considered immunocompromised and are at high risk for serious complications from COVID-19. When COVID started and grew into a huge public health crisis, this population was impacted.  They were already struggling with impaired pulmonary function and other complications. They don't want to go to the emergency room.  They don't want to go to the hospital or the doctor's office.  As a result, we haven't seen these individuals for possibly two years.  Their healthcare stopped because they had to decide, "Do I go into the emergency room or a doctor's office and possibly contract COVID?"  Their general health is much poorer now that they are starting to see their primary care providers and hematologists.

Many have struggled with symptoms and complications that their providers don't even know about. So there has to be some grace in our profession when we want to ask questions like, "Why has a patient had a stroke, and they weren't referred to speech therapy?"  COVID impacted much more than people think. Clinical drugs came to a halt due to COVID. So there has not been much advancement in that area for this population. Patients have been forced to rely on practitioners who provide telemedicine, and they may live in an area where an SLP or audiologist can not see them through telemedicine.

Parents who have children with sickle cell disease are fearful of their children getting COVID. Think about all those areas they're struggling with: writing, language, reading, etc. They're already struggling, and now they're being kept at home. So, a child who's already struggling academically has been kept at home for the last two years and might be reentering into a structured school environment, or the parent might be trying to save their child's life and not have them go back into the classroom where they may contract COVID.

Tips for Supporting Individuals with SCD

There are some tips to consider for supporting individuals with SCD.  If you're working with children who have sickle cell disease, become familiar with their 504 plan. If they don't have a 504, encourage the parents to get them one based on what you now know about sickle cell disease.

Ensure the person has adequate access to hydration. If you're treating someone in a therapy gym, a classroom, or a speech room, make sure that they always have adequate hydration because that helps reduce the crisis and reduces pain. They don't get to "turn off" their sickle cell when they come to the therapy gym. They don't get to take a break from it when they come to see you for therapy, so ensure they have access to the things they need.

We know that temperature impacts the complications of sickle cell disease, especially from a pain standpoint. Be mindful that it's not extremely hot if you're doing activities outside with the patient, and it's not extremely cold in your office, therapy gym, or wherever you treat your patients. Allow accommodations during physical education, recess, and other strenuous activities that you might be doing with this patient.

Watch for signs of stroke. When we monitor sudden changes in cognition, language, and communication function, we're better equipped to tell parents, teachers, and caregivers, that this symptom could indicate that they are having silent cerebral infarcts.

Lastly, maintain open communication with parents and caregivers, so they understand you are available and you are ready and able to assist them.

Summary

In summary, sickle cell disease is a chronic illness affecting every major organ. It can cause progressive deterioration in the quality of life in children and adults. I always say, "Where blood flows, sickle cell goes."  Children and adults with sickle cell disease must be assessed comprehensively and systematically. Most importantly, it is imperative that we screen the speech and hearing of children and adults with sickle cell disease, particularly children who have had strokes.

There is a great need for broader comprehensive care for children and adults with sickle cell disease. Early childhood development and cognitive function evaluations that justify support for educational performance should be supported vigorously by pediatricians, psychologists, therapists, and funders of medical care and research. The playing field and the quality of life for patients with sickle cell disease must be leveled, and it starts with us.

Questions and Answers

Do individuals with sickle cell disease have any normal cells combined with the sickle-shaped cells, or will all of the cells be an irregular shape?

Actually, they do have some cells that are normal and some that are sickle-shaped. The percentage varies from patient to patient based on whether or not the patient has chronic transfusions. If they're on chronic transfusions, then they're going to have some normal AA cells. However, those cells are going to die. And as those die, the body starts to produce its own cells, which are in sickle form. But, again, that percentage varies from patient to patient, and the percentage of SS in someone's body does not paint the big picture of how they feel.  For example, a person with 80% sickle cells in their body may not be feeling any pain, whereas somebody who has 40 or 50% at a given time could be experiencing a high acuity of pain at that point.

Is there any promising future research about ways to change the shapes of the cells or perhaps help the body to produce more normal cells, or, for right now, is transfusion kind of the option?

It's transfusion and hydroxyurea. Hydroxyurea has been shown to keep those cells producing fetal hemoglobin. The idea is that those cells would live longer and would not sickle. It's currently the only drug that does this, and it's been out the longest. The other drugs, L-glutamine, Oxbryta, and Voxelotor, are some of the newer ones, but they have different goals. They do not change the shape. Hydroxyurea is the one that's doing that. Oxbryta does more for anemia by raising the hemoglobin. And these can all be prescribed to patients because they treat different symptoms. 

When you were talking about the incidence of sensorineural hearing loss, and this population is somewhat tied to the vaso-occlusion crises, does the hearing loss happens later?  Or does it happen more immediately during the crisis, then it resolves and deteriorates again with the next crisis?

Research suggests sensorineural hearing loss is more permanent in patients with frequent crises. However, there are patients who experience hearing loss with a crisis and then say that it resolves. So, it's kind of a sudden hearing loss, and then it resolves as the crisis and as the pain leans off. But some research shows that these patients start to experience more permanent hearing loss for various reasons (e.g., frequent otitis media, crises, hidden hearing loss).  There are a lot of theories that speak to why someone could perceive that they have hearing loss, although they present with normal hearing thresholds.

With the hidden hearing loss, you said there are pure tone thresholds. But do patients show any decrease in speech discrimination scores or other audiological types of tests? Or does everything score normal, and the person, perceptually, is having trouble?

They struggle with the functional aspects. They can't process, and it's almost like a central auditory processing disorder for them.

References

Armstrong, D. F., Thompson, R. J., Winfred Wang, M. D., Robert Zimmerman, M. D., Charles, H., Pegelow, M. D., Vass, K. (1996). Cognitive functioning and brain magnetic resonance imaging in children with sickle cell disease. Pediatrics.

Balkaran, B., Char, G., Morris, J. S., Thomas, P. W., Serjeant, B. E., & Serjeant, G. R. (1992). Stroke in a cohort of patients with homozygous sickle cell disease. The Journal of Pediatrics.

Buchanan, I. D., James-Herry, A., & Osunkwo, I. (2013). The other side of abnormal: A case series of low transcranial doppler velocities associated with stroke in children with sickle cell disease. Journal of Pediatric Hematology/Oncology.

Centers for Disease Control and Prevention. (2020). Data & Statistics on Sickle Cell Disease | CDC. Retrieved December 2, 2020, from https://www.cdc.gov/ncbddd/sicklecell/data.html

Dale, J. C., Cochran, C. J., Roy, L., Jernigan, E., & Buchanan, G. R. (2011). Health-related Quality of Life in Children and Adolescents With Sickle Cell Disease. Journal of Pediatric Health Care.

Davis, P., Landers, A., Gentry, B., Montague, J., Dancer, J., Jackson, J., & Williams, L. (1997). Speech and language characteristics of children with strokes due to sickle cell disease. Perceptual and Motor Skills.

De Oliveira, C. C., Ciasca, S. M., & Moura-Ribeiro, M. V. L. (2008). Stroke in patients with sickle cell disease: Clinical and neurological aspects. Arquivos de Neuro-Psiquiatria.

Dyson, S. M., Abuateya, H., Atkin, K., Culley, L., Dyson, S. E., & Rowley, D. (2010). Reported school experiences of young people living with sickle cell disorder in England. British Educational Research Journal.

Earley, C. J., Kittner, S. J., Feeser, B. R., Gardner, J., Epstein, A., Wozniak, M. A., … Buchholz, D. (1998). Stroke in children and sickle-cell disease: Baltimore-Washington cooperative young stroke study. Neurology.

Hariman, L. M. F., Griffith, E. R., Hurtig, A. L., & Keehn, M. T. (1991). Functional outcomes of children with sickle-cell disease affected by stroke. Archives of Physical Medicine and Rehabilitation.

Kawadler, J. M., Clayden, J. D., Clark, C. A., & Kirkham, F. J. (2016). Intelligence quotient in paediatric sickle cell disease: a systematic review and meta-analysis. Developmental Medicine and Child Neurology. https://doi.org/10.1111/dmcn.13113

King, A. A., DeBaun, M. R., & White, D. A. (2008). Need for cognitive rehabilitation for children with sickle cell disease and strokes. Expert Review of Neurotherapeutics.

Knight-Madden, J. M., Barton-Gooden, A., Weaver, S. R., Reid, M., & Greenough, A. (2013). Mortality, asthma, smoking and acute chest syndrome in young adults with sickle cell disease. Lung.

Maitra, P., Caughey, M., Robinson, L., Desai, P. C., Jones, S., Nouraie, M., Ataga, K. I. (2017). Risk factors for mortality in adult patients with sickle cell disease: A meta-analysis of studies in North America and Europe. Haematologica.

Miller, S. T., Sleeper, L. A., Pegelow, C. H., Enos, L. E., Wang, W. C., Weiner, S. J., Kinney, T. R. (2000). Prediction of adverse outcomes in children with sickle cell disease. New England Journal of Medicine.

Ohene-Frempong, K., Weiner, S. J., Sleeper, L. A., Miller, S. T., Embury, S., Moohr, J. W., … Gill, F. M. (1998). Cerebrovascular accidents in sickle cell disease: Rates and risk factors. Blood.

Sanders, C., Gentry, B., Davis, P., Jackson, J., Saccente, S., & Dancer, J. (1997). Reading, writing, and vocabulary skills of children with strokes due to sickle cell disease. Perceptual and Motor Skills.

Saricoban, H. E., Ozen, A., Harmanci, K., Razi, C., Zahmacioglu, O., & Cengizlier, M. R. (2011). Common behavioral problems among children with asthma: Is there a role of asthma treatment? Annals of Allergy, Asthma and Immunology.

Schatz, J. (2004). Brief report: Academic attainment in children with sickle cell disease. Journal of Pediatric Psychology.

Schatz, J., Puffer, E. S., Sanchez, C., Stancil, M., & Roberts, C. W. (2009). Language processing deficits in sickle cell disease in young school-age children. Developmental Neuropsychology.

Sharma, S., Hashmi, M. F., & Chakraborty, R. K. (2020). Asthma medications. StatPearls - NCBI Bookshelf, 40(SUPPL.), 19–22.