The association between sleep disturbances and neurocognitive function in pediatric sickle cell disease

BACKGROUND AND OBJECTIVE

Youth with sickle cell disease (SCD) without neurological complications continue to be at increased risk of neurocognitive difficulties. Nocturnal hypoxemia is associated with neurocognitive outcomes and has been identified as a chronic complication in youth with SCD. The objective of this study was to assess the relationship between sleep disturbances and neurocognitive functioning in youth with SCD, while taking into account demographic and socioeconomic factors.

METHODS

Youth with SCD were identified through retrospective chart review who underwent a standardized polysomnography (PSG) and completed a neuropsychological testing battery to assess cognitive skills, including verbal comprehension, working memory, processing speed, and cognitive flexibility. Questionnaires were also collected to assess parent-reported concerns with their youth's executive and adaptive skills.

RESULTS

Twenty-seven youth with SCD, ages 6-17, were identified who completed both a PSG and neuropsychological testing. Results demonstrated that verbal comprehension decreased by 2.37 standard points for every unit decrease in mean nocturnal oxygen saturation (SpO2) (p = 0.031). Working memory was also found to decrease by 1.46 standard points for each 1% increase in time spent under 90% oxygen saturation (pTST SpO2 < 90%) (p = 0.030). Sleep parameters did not significantly predict other cognitive scores or parent-reported executive or behavioral ratings.

CONCLUSION

Our study found that sleep disturbance, mean nocturnal SpO2 and pTST SpO2 < 90%, significantly affected verbal comprehension and working memory performance, respectively. Overall, these findings have the potential to identify sleep needs in youth with SCD to promote sleep-targeted interventions as a modifiable factor to reduce neurocognitive deficits.

Mycoplasma pneumoniae Carriage With De Novo Macrolide-Resistance and Breakthrough Pneumonia

Mycoplasma pneumoniae pneumonia is prevalent in children and can be followed by upper airway carriage for months. Treatment of M pneumoniae pneumonia with macrolides is widespread and can lead to the development of macrolide resistance. The clinical consequences of chronic M pneumoniae carriage are unknown. In this article, we describe a child with acute lymphoblastic leukemia who developed macrolide-susceptible M pneumoniae pneumonia confirmed by nasopharyngeal secretions polymerase chain reaction and culture with good response to azithromycin. Five months later, the patient developed another M pneumoniae pneumonia that was diagnosed with positive macrolide-resistant M pneumoniae polymerase chain reaction and culture from the bronchoalveolar lavage. The child responded well to fluoroquinolones and eventually was discharged from the hospital. The M pneumoniae recovered from the second pneumonia is a novel strain and is genetically identical to the M pneumoniae that caused the first pneumonia, apart from the macrolide-resistance 23S ribosomal RNA gene. Both isolates are identical in both P1 (subtype 2 with a novel variant, 2bv) and multiple-locus variable number tandem repeat analysis type (53662). This is indicative of chronic M pneumoniae carriage with de novo macrolide-resistance mutation and subsequent breakthrough pneumonia that is reported for the first time here. Children with immunosuppression may be at increased risk of life-threatening macrolide-resistant pneumonia after M pneumoniae carriage. Further studies are required to evaluate the impact of this phenomenon. This will then guide strategies to limit the associated morbidity, such as testing for macrolide resistance, treatment of M pneumoniae pneumonia in high-risk children with bactericidal antibiotics (such as fluoroquinolones), and possibly eradication protocols of M pneumoniae carriage to prevent subsequent life-threatening infections.

Nocturnal hypoxemia measured by polysomnogram is associated with acute chest syndrome in pediatric sickle cell disease

STUDY OBJECTIVES

Nocturnal hypoxemia is associated with increased risk of sickle cell disease (SCD) complications. The association of nighttime hypoxemia and acute chest syndrome (ACS) in children with SCD has yet to be determined.

METHODS

This is a retrospective study of children with SCD who underwent polysomnography at a SCD center. Univariate logistic regression was used to assess the association between nocturnal hypoxemia and ACS admissions. Multivariate logistic regression was performed to verify the effects of different clinical covariates on ACS. Secondary analysis comparing patients with one vs multiple ACS admissions was performed.

RESULTS

One hundred ten individuals with SCD who completed their polysomnogram (mean age of 9.4 years) were identified. Fifty-nine (54%) had a history of at least one episode of ACS admission (mean age of 4.1 years), including 40 with multiple episodes. The percentage of total sleep time with O₂ saturation < 90% was greater in the ACS group (P < .05). Similarly, mean nocturnal O₂ saturation was lower in the ACS group (P < .0005). Mean nocturnal O₂ saturation of < 97.3% and the percentage of total sleep time with O₂ saturation < 90% higher than 2.7% were associated with ACS. There was no difference in nocturnal hypoxemia between patients with single and multiple ACS admissions.

CONCLUSIONS

Nocturnal hypoxemia later in life is associated with previous ACS admissions in children with SCD. This can increase the yield of interpreting polysomnograms in this vulnerable population. Prospective studies are needed to determine the temporal relations of nocturnal hypoxemia and ACS, which may identify a modifiable risk for ACS.

Chlorine inhalation induces acute chest syndrome in humanized sickle cell mouse model and ameliorated by postexposure hemopexin

Triggering factors of Acute Chest Syndrome (ACS) is a leading cause of death in patients with Sickle Cell Disease (SCD) and targeted therapies are limited. Chlorine (Cl2) inhalation happens frequently, but its role as a potential trigger of ACS has not been determined. In this study, we hypothesized that Cl2 exposure resembling that in the vicinity of industrial accidents induces acute hemolysis with acute lung injury, reminiscent of ACS in humanized SCD mice. When exposed to Cl2 (500 ppm for 30 min), 64% of SCD mice succumbed within 6 h while none of the control mice expressing normal human hemoglobin died (p<0.01). Surviving SCD mice had evidence of acute hemolysis, respiratory acidosis, acute lung injury, and high concentrations of chlorinated palmitic and stearic acids (p<0.05) in their plasmas and RBCs compared to controls. Treatment with a single intraperitoneal dose of human hemopexin 30 min after Cl2 inhalation reduced mortality to around 15% (p<0.01) with reduced hemolysis (decreased RBCs fragility (p<0.001) and returned plasma heme to normal levels (p<0.0001)), improved oxygenation (p<0.0001) and reduced acute lung injury scores (p<0.0001). RBCs from SCD mice had significant levels of carbonylation (which predisposes RBCs to hemolysis) 6 h post-Cl2 exposure which were absent in RBCs of mice treated with hemopexin. To understand the mechanisms leading to carbonylation, we incubated RBCs from SCD mice with chlorinated lipids and identified sickling and increased hemolysis compared to RBCs obtained from control mice and treated similarly. Our study indicates that Cl2 inhalation induces ACS in SCD mice via induction of acute hemolysis, and that post exposure administration of hemopexin reduces mortality and lung injury. Our data suggest that SCD patients are vulnerable in Cl2 exposure incidents and that hemopexin is a potential therapeutic agent.

Acute chest syndrome in pediatric sickle cell disease: Associations with racial composition and neighborhood deprivation

BACKGROUND

Acute chest syndrome (ACS) is the leading cause of death for children with sickle cell disease (SCD). Recurrent ACS has detrimental effects on pulmonary health and health care costs. Neighborhood characteristics affect the outcomes of many pediatric chronic diseases, but their role in SCD is not well studied. In this study, we investigated the effects of area-level socioeconomic deprivation and racial composition on the recurrence of ACS.

STUDY DESIGN

We performed a retrospective cross-sectional analysis of clinical data from a large pediatric SCD center. Patients' residential addresses were geocoded and linked to a composite area deprivation index (ADI) and percent African American population at the level of Census block groups. The association of recurrent ACS with neighborhood characteristics was evaluated using logistic regression analysis.

RESULTS

The sample included 709 children with SCD. Residence in a socioeconomically deprived neighborhood was associated with 27% less risk of recurrent ACS, and residence in a predominantly African American neighborhood was associated with 41% less risk of ACS recurrence. The racial composition explained the protective effect of living in a high-deprivation area after adjusting for sociodemographic and clinical covariates. Demographic and clinical factors associated with recurrent ACS included older age, male gender, asthma, hydroxyurea use, and chronic transfusion therapy.

CONCLUSIONS

This is the first study to report a protective effect of residing in a predominantly African American community for ACS recurrence. Further prospective studies are needed to confirm the association and to understand the mechanisms of such relationship.

Allergic airway sensitization impairs antibacterial IgG antibody responses during bacterial respiratory tract infections

BACKGROUND

Mycoplasma pneumoniae, an atypical human pathogen, has been associated with asthma initiation and exacerbation. Asthmatic patients have been reported to have higher carriage rates of M pneumoniae compared with nonasthmatic subjects and are at greater risk for invasive respiratory infections.

OBJECTIVE

We sought to study whether prior allergen sensitization affects the host response to chronic bacterial infection.

METHODS

BALB/cJ and IL-4 receptor α^-/- mice were sensitized with ovalbumin (OVA) and then infected with M pneumoniae or Streptococcus pneumoniae. Immune parameters were analyzed at 30 days postinfection and included cellular profiles in bronchoalveolar lavage fluid (BALF) and serum IgG and IgE antibody levels to whole bacterial lysate, recombinant P1 adhesin, and OVA. Total lung RNA was examined for transcript levels, and BALF was examined for cytokine protein profiles.

RESULTS

Anti-M pneumoniae antibody responses were decreased in allergen-sensitized, M pneumoniae-infected animals compared with control animals, but OVA-specific IgG responses were unaffected. Similar decreases in anti-S pneumoniae antibody levels were found in OVA-sensitized animals. However, M pneumoniae, but not S pneumoniae, infection augmented anti-OVA IgE antibody responses. Loss of IL-4 receptor signaling partially restored anti-M pneumoniae antibody responses in IgG_2a and IgG_2b subclasses. Inflammatory cytokine levels in BALF from OVA-sensitized, M pneumoniae-infected or S pneumoniae-infected animals were reduced compared with those in uninfected OVA-sensitized control animals. Unexpectedly, airway hyperreactivity to methacholine was essentially ablated in M pneumoniae-infected, OVA-sensitized animals.

CONCLUSIONS

An established type 2-biased host immune response impairs the host immune response to respiratory bacterial infection in a largely pathogen-independent manner. Some pathogens, such as M pneumoniae, can augment ongoing allergic responses and inhibit pulmonary type 2 cytokine responses and allergic airway hyperreactivity.

Association of elevated tricuspid regurgitation velocity with cerebrovascular and kidney disease in children with sickle cell disease

BACKGROUND

Tricuspid regurgitation velocity (TRV), measured by echocardiography, is a surrogate marker for pulmonary hypertension. Limited pediatric studies have considered the association between TRV and surrogate markers of end-organ disease.

METHODS

We conducted a cross-sectional study that evaluated the prevalence of elevated TRV ≥2.5 m/s and its associations with renal and cerebrovascular outcomes in children with sickle cell disease (SCD) 1-21 years of age in two large sickle cell cohorts, the University of Alabama at Birmingham (UAB) sickle cell cohort, and the Sickle Cell Clinical Research and Intervention Program (SCCRIP) cohort at St. Jude Children's Research Hospital. We hypothesized that patients with SCD and elevated TRV would have higher odds of having either persistent albuminuria or cerebrovascular disease.

RESULTS

We identified 166 children from the UAB cohort (mean age: 13.49 ± 4.47 years) and 325 children from the SCCRIP cohort (mean age: 13.41 ± 3.99 years) with echocardiograms. The prevalence of an elevated TRV was 21% in both UAB and SCCRIP cohorts. Elevated TRV was significantly associated with cerebrovascular disease (odds ratio [OR] 1.88, 95% confidence interval [CI]: 1.12-3.15; p = .017) and persistent albuminuria (OR 1.81, 95% CI: 1.07-3.06; p = .028) after adjusting for age, sex, treatment, and site.

CONCLUSION

This cross-sectional, multicenter study identifies associations between surrogate markers of pulmonary hypertension with kidney disease and cerebrovascular disease. A prospective study should be performed to evaluate the longitudinal outcomes for patients with multiple surrogate markers of end-organ disease.

Pediatric Chronic Pulmonary Aspiration Is Associated With Low Molecular Weight Hyaluronic Acid in the Bronchoalveolar Lavage

OBJECTIVES

Low molecular-weight hyaluronic acid (LMW-HA) is produced by the degradation of high-molecular-weight hyaluronic acid at the pulmonary interstitium and alveolar epithelium by reactive intermediates following lung injury. We aimed to investigate the role of bronchoalveolar lavage (BAL) LMW-HA as a biomarker of pediatric chronic pulmonary aspiration (CPA).

METHODS

Single-center prospective comparison of LMW-HA presence in BAL in pediatric Aerodigestive patients with and without CPA undergoing clinically indicated bronchoscopy. Pediatric pulmonologists diagnosed CPA based on video-fluoroscopic swallowing evaluation.

RESULTS

Fifteen children (mean age 6.1 years, male predominance at 73%, and 53% with CPA) were enrolled. Children with CPA have comparable baseline characteristics (age, sex, and race), but their BAL had higher white blood cell count, higher neutrophil percentages, higher bacterial culture positivity rates, and lower macrophage percentages than those without CPA. The two groups were comparable in sex, BAL lymphocyte percentages, eosinophil percentages, red blood cell counts, and lipid-laden macrophage positivity. Detection of BAL LMW-HA in the BAL had a 100% specificity and 88% sensitivity for CPA diagnosis. BAL protein levels were higher in the CPA group and in participants with positive LMW-HA.

CONCLUSIONS

We suggest BAL LMW-HA as a potential novel biomarker of pediatric CPA with high specificity and sensitivity. BAL LMW-HA is not detectable in subjects without CPA and is associated with increased BAL protein levels.

Hemopexin reverses activation of lung eIF2α and decreases mitochondrial injury in chlorine-exposed mice

We assessed the mechanisms by which nonencapsulated heme, released in the plasma of mice after exposure to chlorine (Cl2) gas, resulted in the initiation and propagation of acute lung injury. We exposed adult male and female C57BL/6 mice to Cl2 (500 ppm for 30 min), returned them to room air, and injected them intramuscularly with either human hemopexin (hHPX; 5 µg/g BW in 50-µL saline) or vehicle at 1 h post-exposure. Upon return to room air, Cl2-exposed mice, injected with vehicle, developed respiratory acidosis, increased concentrations of plasma proteins in the alveolar space, lung mitochondrial DNA injury, increased levels of free plasma heme, and major alterations of their lung proteome. hHPX injection mice mitigated the onset and development of lung and mitochondrial injury and the increase of plasma heme, reversed the Cl2-induced changes in 83 of 237 proteins in the lung proteome at 24 h post-exposure, and improved survival at 15 days post-exposure. Systems biology analysis of the lung global proteomics data showed that hHPX reversed changes in a number of key pathways including elF2 signaling, verified by Western blotting measurements. Recombinant human hemopexin, generated in tobacco plants, injected at 1 h post-Cl2 exposure, was equally effective in reversing acute lung and mtDNA injury. The results of this study offer new insights as to the mechanisms by which exposure to Cl2 results in acute lung injury and the therapeutic effects of hemopexin.NEW & NOTEWORTHY Herein, we demonstrate that exposure of mice to chlorine gas causes significant changes in the lung proteome 24 h post-exposure. Systems biology analysis of the proteomic data is consistent with damage to mitochondria and activation of eIF2, the master regulator of transcription and protein translation. Post-exposure injection of hemopexin, which scavenges free heme, attenuated mtDNA injury, eIF2α phosphorylation, decreased lung injury, and increased survival.

Hemopexin Reverses Activation of Lung eIF2a and Decreases Mitochondrial Injury in Chlorine Exposed Mice

We assessed the mechanisms by which non-encapsulated heme, released in the plasma of mice post exposure to chlorine (Cl 2 ) gas, resulted in the initiation and propagation of acute lung injury. We exposed adult C57BL/6 male and female to Cl 2 (500 ppm for 30 min) in environmental chambers and returned them to room air and injected them intramuscularly with a single dose of human hemopexin (hHPX; 5 µg/ g BW), the most efficient scavenger of heme, 30-60 min post exposure. Concentrations of hHPX in plasma of air and Cl 2 exposed mice were 9081±900 vs. 1879± 293 at 6 h and 2966±463 vs. 1555±250 at 50 h post injection (ng/ml; X±1 SEM=3; p<0.01). Cl 2 exposed mice developed progressive acute lung injury post exposure characterized by increased concentrations of plasma heme, marked inflammatory response, respiratory acidosis and increased concentrations of plasma proteins in the alveolar space. Injection of hHPX decreased the onset of acute lung injury at 24 h post exposure; mean survival, for the saline and hHPX groups were 40 vs. 80% (P<0.001) at 15 d post exposure. Non-supervised global proteomics analysis of mouse lungs at 24 h post exposure, revealed the upregulation of 92 and downregulation of 145 lung proteins. Injection of hHPX at one h post exposure moderated the Cl 2 induced changes in eighty-three of these 237 lung proteins. System biology analysis of the global proteomics data showed that hHPX reversed changes in mitochondrial dysfunction and elF2 and integrin signaling. Western blot analysis of lung tissue showed significant increase of phosphorylated elF2 at 24 h post exposure in vehicle treated mice but normal levels in those injected with hHPX. Similarly, RT-PCR analysis of lung tissue showed that hHPX reversed the onset of mtDNA lesions. A form of recombinant human hemopexin generated in tobacco plants was equally effective in reversing acute lung and mtDNA injury. The results of this study offer new insights as to the mechanisms by which exposure to Cl 2 results in acute lung injury and to the therapeutic effects of hemopexin.

Biomarkers to Differentiate Acute Chest Syndrome From Vaso-Occlusive Crisis in Children With Sickle Cell Disease

BACKGROUND

Acute Chest Syndrome (ACS) is the leading cause of death in children with sickle cell disease (SCD) in the US-about half of the children who develop ACS present initially with pain.

METHODS

Here, we studied biomarkers to differentiate ACS from vaso-occlusive crises (VOC) in children with SCD who presented with pain to the emergency department (ED). We conducted a prospective cohort study of consecutive patients who presented to the ED with pain and were discharged with ACS or VOC between March, 2017 and February, 2020.

RESULTS

We identified 7 patients with ACS and 19 patients with VOC. The two groups were comparable in age and sex. All patients with ACS had asthma versus 42% of the VOC group. The ACS group had lower weight and BMI z-scores. Patients with ACS compared to VOC had significantly higher respiratory rates, lower O2 saturation, and longer hospital stays. They also had higher white blood cell count, glucose level (> 99 mg/dL), anion gap (> 9 mEq/L), sPLA2 (> 7 pg/mL), IFN-γ (> 17.8 pg/mL), IL-10 (1.54 pg/mL), and IL-12 (> 0.5 pg/mL) levels.

CONCLUSIONS

We identified biomarkers associated with ACS development in children with SCD presenting with pain that allow for earlier ACS interventions to reduce mortality and morbidity.

Multicenter comparative study of polysomnography outcomes in children with the monogenic disorder sickle cell disease

STUDY OBJECTIVES

Sleep-disordered breathing is prevalent in children with sickle cell disease (SCD) and is associated with worse outcomes. This study aimed to compare the outcomes of polysomnography (PSG) performed for pediatric patients with SCD at 3 US centers.

METHODS

We included patients with SCD aged 0-21 years who underwent PSG at 3 American Academy of Sleep Medicine-accredited centers, the University of Alabama at Birmingham, the University of Florida, and Duke University Hospital, between 2012 and 2022. Descriptive statistics were used as appropriate to compare the baseline characters and PSG outcomes among the different centers.

RESULTS

A total of 210 children with SCD from the 3 centers were included, with comparable sex, SCD genotypes, hemoglobin, hematocrit levels, and chronic transfusion. Children from the different centers exhibited variations in age (P < .001), body mass index (P < .05), mean corpuscular volume (P < .05), and hydroxyurea usage (P < .05) at the time of the PSG. Overall, the 3 centers showed significantly different PSG outcomes. Patients from the University of Florida had worse obstructive sleep apnea, oxygenation, and periodic leg movement events, together with lower hydroxyurea usage, and those from Duke University Hospital showed higher hypoventilation and arousal indices.

CONCLUSIONS

This multicenter study underscores variations in PSG outcomes among pediatric SCD patients at different centers in the southeastern United States. These findings emphasize the need for standardized approaches to screen for sleep-disordered breathing, refer to PSG, and interpret the results in children with SCD. These conclusions may apply to other genetic disorders associated with an increased risk of sleep-disordered breathing.

CITATION

Alishlash AS, Nourani AR, Lebensburger J, Rothman JA, Ali-Dinar T, Ezmigna D. Multicenter comparative study of polysomnography outcomes in children with the monogenic disorder sickle cell disease. J Clin Sleep Med. 2025;21(2):297-304.