Environmental influences on daily emergency admissions in sickle-cell disease patients

Updates in Pediatric Sickle Cell Lung Disease

Sickle cell lung disease presents a challenging care paradigm involving acute and chronic lower airway disease, sleep-disordered breathing, pulmonary vascular disease, and modification by environmental factors. Understanding the presentation, pathophysiology, and diagnostic approaches is essential for accurate identification and management. While significant progress has been made, there remains a need for research to develop effective treatments and interventions to decrease disease burden in these children. Additionally, the long-term impact of interventions on cardiopulmonary outcomes is unknown. Collaborative efforts among health care providers, researchers, advocacy groups, and policy makers are crucial to improving the lives of children with SCD.

Outdoor Air Pollution and Pediatric Respiratory Disease

Outdoor air pollution is ubiquitous, and no safe level of exposure has been identified for the most common air pollutants such as ozone and particle pollution. Children are uniquely more susceptible to the harms of outdoor air pollution, which can cause and exacerbate respiratory disease. Although challenging to identify the effects of outdoor air pollution on individual patients, understanding the basics of outdoor air pollution is essential for pediatric respiratory health care providers. This review covers basic information regarding outdoor air pollution, unique considerations for children, mechanisms for increased susceptibility, and association with incident and exacerbation of respiratory disease in children.

Meteorological parameters and hospitalizations of patients with sickle cell anemia: a 20-year retrospective study in Campinas, São Paulo, Brazil

To investigate the influence of climate on hospitalizations of sickle cell anemia (SCA) adults and children, we analyzed the health and meteorological parameters from a metropolis (1999-2018). 1462 hospitalizations were coded for SCA patients in crisis (M:F = 715:747) and 1354 hospitalizations for SCA patients without crisis (M:F = 698:656) [age = 22.9 vs 15.2 years and duration of hospitalization (DoH) = 5.7 vs 4.4 days, respectively,]. More hospitalizations were for adults than children in crisis, and for children than adults without crisis. More children and adults were hospitalized in winter andspring than in summer and autumn     Hospitalizations correlated positively with humidity (lag -5), maximum pressure (lag -2), mean pressure (lag -2), and thermal amplitude (lag -2), and negatively with maximum temperature (lag -3). DoH positively correlated with minimum temperature (lag -4). Understanding these complex associations would induce attitudinal/behavioral modifications among patients and their caregivers.

Exploration de l’hémolyse associée à la drépanocytose et perspectives thérapeutiques spécifiques

Sickle Cell Anemia is a disease with a strong vascular tropism. Beyond anemia, the pathophysiological mechanisms responsible for hemolysis, directly affect both acute and chronic vascular damages, thus resulting in a systemic disease. Understanding the different types of hemolysis underline the need for novel specific biomarkers. Targeted therapeutic approaches for these pathophysiological pathways are necessary to improve Sickle Cell patients' prognosis. Finally, given its complexity, Sickle Cell Disease is often used as a "proof of concept" for other pathologies. It seems likely that the rapidly evolving knowledge in this field will also benefit other diseases. © 2023 Société nationale française de médecine interne (SNFMI). Published by Elsevier Masson SAS. All rights reserved.

Association of haemolysis markers, blood viscosity and microcirculation function with organ damage in sickle cell disease in sub-Saharan Africa (the BIOCADRE study)

Sickle cell anaemia (SCA) is a monogenic disease with a highly variable clinical course. We aimed to investigate associations between microvascular function, haemolysis markers, blood viscosity and various types of SCA-related organ damage in a multicentric sub-Saharan African cohort of patients with SCA. In a cross-sectional study, we selected seven groups of adult patients with SS phenotype in Dakar and Bamako based on the following complications: leg ulcer, priapism, osteonecrosis, retinopathy, high tricuspid regurgitant jet velocity (TRV), macro-albuminuria or none. Clinical assessment, echocardiography, peripheral arterial tonometry, laboratory tests and blood viscosity measurement were performed. We explored statistical associations between the biological parameters and the six studied complications. Among 235 patients, 58 had high TRV, 46 osteonecrosis, 43 priapism, 33 leg ulcers, 31 retinopathy and 22 macroalbuminuria, whereas 36 had none of these complications. Multiple correspondence analysis revealed no cluster of complications. Lactate dehydrogenase levels were associated with high TRV, and blood viscosity was associated with retinopathy and the absence of macroalbuminuria. Despite extensive phenotyping of patients, no specific pattern of SCA-related complications was identified. New biomarkers are needed to predict SCA clinical expression to adapt patient management, especially in Africa, where healthcare resources are scarce.

Ozone and childhood respiratory health: A primer for US pediatric providers and a call for a more protective standard

Ground level ozone is a potent respiratory toxicant with decades of accumulated data demonstrating respiratory harms to children. Despite the ubiquity of ozone in the United States, impacting both urban and rural communities, the associated harms of exposure to this important air pollutant are often infrequently or inadequately covered during medical training including pulmonary specialization. Thus, many providers caring for children's respiratory health may have limited knowledge of the harms which may result in reduced discussion of ozone pollution during clinical encounters. Further, the current US air quality standard for ozone does not adequately protect children. In this nonsystematic review, we present basic background information for healthcare providers caring for children's respiratory health, review the US process for setting air quality standards, discuss the respiratory harms of ozone for healthy children and those with underlying respiratory disease, highlight the urgent need for a more protective ozone standard to adequately protect children's respiratory health, review impacts of climate change on ozone levels, and provide information for discussion in clinical encounters.

[Lung manifestations of sickle-cell disease]

Sickle-cell disease is an autosomal recessive genetic disorder of hemoglobin that causes systemic damage. Hypoxia is the main actor of sickle-cell disease. It initiates acutely the pathogenic cascade leading to tissue damages that in turn induce chronic hypoxia. Lung lesions represent the major risk of morbidity and mortality. Management of sickle-cell disease requires a tight collaboration between hematologists, intensivists and chest physicians. Recurrent episodes of thrombosis and hemolysis characterize the disease. New therapeutic protocols, associating hydroxyurea, transfusion program and stem cell transplantation in severe cases allow a prolonged survival until the fifth decade. However, recurrent pain, crisis, frequent hospital admissions due to infection, anemia or acute chest syndrome and chronic complications leading to organ deficiencies degrade the patients' quality of life. In low-income countries where the majority of sickle-cell patients are living, the disease is still associated with a high mortality in childhood. This paper focuses on acute chest syndrome and chronic lung manifestations.

Environmental Factors in Northern Italy and Sickle Cell Disease Acute Complications: A Multicentric Study

BACKGROUND

Environmental factors seem to influence clinical manifestations of sickle cell disease (SCD), but few studies have shown consistent findings. We conducted a retrospective multicentric observational study to investigate the influence of environmental parameters on hospitalization for vaso-occlusive crises (VOC) or acute chest syndrome (ACS) in children with SCD.

METHODS

Hospital admissions were correlated with daily meteorological and air-quality data obtained from Environmental Regional Agencies in the period 2011-2015. The effect of different parameters was assessed on the day preceding the crisis up to ten days before. Statistical analysis was performed using a quasi-likelihood Poisson regression in a generalized linear model.

RESULTS

The risk of hospitalization was increased for low maximum temperature, low minimum relative humidity, and low atmospheric pressure and weakly for mean wind speed. The diurnal temperature range and temperature difference between two consecutive days were determined to be important causes of hospitalization. For air quality parameters, we found a correlation only for high levels of ozone and for low values at the tail corresponding to the lowest concentration of this pollutant.

CONCLUSIONS

Temperature, atmospheric pressure, humidity and ozone levels influence acute complications of SCD. Patients' education and the knowledge of the modes of actions of these factors could reduce hospitalizations.

Prise en charge d’un patient drépanocytaire aux urgences

La drépanocytose est aujourd’hui la première maladie génétique en France avec environ 30 000 patients adultes. Une mutation ponctuelle sur le chromosome 11 conduit à la production d’une hémoglobine pathologique qui polymérise sous l’effet de facteurs endo-ou exogènes induisant la falciformation des globules rouges à l’origine d’une vasoocclusion artérielle dont une des conséquences est l’oblitération des vaisseaux à destinée osseuse. Les infarctus osseux sont particulièrement douloureux, conduisant les patients aux urgences où l’enjeu est de soulager rapidement les douleurs par l’utilisation de morphine principalement par analgésie autocontrôlée après titration morphinique. Le risque majeur au cours de ces crises vaso-occlusives (CVO) est l’apparition d’un syndrome thoracique aigu (STA) pouvant mettre en jeu le pronostic vital du patient. La spirométrie incitative est un moyen préventif du STA important à instituer dès les urgences. Une antibiothérapie sera mise en place en cas de fièvre chez ces patients aspléniques à risque d’infections à germes encapsulés notamment par le pneumocoque. L’échange transfusionnel est une des pierres angulaires du traitement des CVO ou du STA mais le risque d’accident hémolytique aigu post transfusionnel doit en limiter l’usage à des situations mettant en jeu le pronostic vital ou fonctionnel d’organe. Plusieurs scores clinicobiologiques permettent de décider de l’utilité d’un angioscanner thoracique au cours du STA à la recherche d’une embolie pulmonaire ou pour décider de la pertinence d’une sortie vers une hospitalisation à domicile (Programme DREPADOM). L’utilisation de la morphine en dehors de l’hôpital de façon prolongée doit être prudente en raison du risque d’addiction.

Determinants of severity in sickle cell disease

Sickle cell disease is a very variable condition, with outcomes ranging from death in childhood to living relatively symptom free into the 8^th decade. Much of this variability is unexplained. The co-inheritance of α thalassaemia and factors determining HbF levels significantly modify the phenotype, but few other significant genetic variants have been identified, despite extensive studies. Environmental factors are undoubtedly important, with socio-economics and access to basic medical care explaining the huge differences in outcomes between many low- and high-income countries. Exposure to cold and windy weather seems to precipitate acute complications in many people, although these effects are unpredictable and vary with geography. Many studies have tried to identify prognostic factors which can be used to predict outcomes, particularly when applied in infancy. Overall, low haemoglobin, low haemoglobin F percentage and high reticulocytes in childhood are associated with worse outcomes, although again these effects are fairly weak and inconsistent.

Compound heterozygosity for hemoglobin S and hemoglobin E in a family of Proto-Australoid origin: a case report

Background

Hemoglobin S and E are commonly occurring hemoglobin variants among distinctly separate tribal populations of Central and Northeast India, respectively. Combined heterozygosity for hemoglobin S and E or hemoglobin SE disease is a benign clinical condition with rare incidence. Reports of approximately 46 hemoglobin SE cases are available worldwide. We conducted a screening program to study the prevalence of hemoglobin variants among the tribal population working in the tea estates of Northeast India. A total of 551 subjects were screened, and complete blood count was performed. Based on their hematological profiles, hemoglobin typing was done for 218 subjects.

Case presentation

We describe a case of an adolescent male of Munda tribe diagnosed as double heterozygous for hemoglobin S and E. On screening of the nuclear family of the subject, the mother was found to have hemoglobin E disease and father as hemoglobin S trait. Both siblings of the subject were diagnosed as hemoglobin E trait.

Conclusion

This is the first case of compound heterozygous for hemoglobin S and E to be reported from the tea tribes of Assam, India.

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.

OCCURRENCE OF UNUSUAL HAEMOGLOBINOPATHIES IN BALOCHISTAN: HB SD AND HB SE - PRESENTATION WITH OSTEOMYELITIS

OBJECTIVE

To describe two cases of unusual variants of sickle cell disease.

CASE DESCRIPTION

We present two cases of sickle cell disease variants (haemoglobinopathies), from unrelated families, in the state of Balochistan (Pakistan). One was diagnosed with sickle cell disease in the haemoglobin electrophoresis, whereas the other was diagnosed with sickle cell SE disease. Both were diagnosed based on the presentation of osteomyelitis.

COMMENTS

Haemoglobin SD disease (Hb SD) and haemoglobin SE disease (Hb SE) are rare haemoglobinopathies in the world. The lack of available literature suggests that both are variants of sickle cell disease (SCD), with heterogeneous nature. The prevalence of sickle cell disease with compound heterozygotes was found at a variable frequency in the population of the Asian Southeast. The frequency of osteomyelitis in SCD is 12 to 18%, but its occurrence among variant haemoglobinopathies is little reported. Both reported cases presented with osteomyelitis as a characteristic of the disease presentation.

Influence of Nutrition on Disease Severity and Health-related Quality of Life in Adults with Sickle Cell Disease: A Prospective Study

Background & Aims

Sickle cell disease (SCD), a genetic disorder resulting from the presence of a mutated hemoglobin S (HbS), has a worldwide distribution and causes significant morbidity and mortality in children and adults. Few studies addressed the determinants of SCD severity in adults; therefore, we investigated the impact of nutrition on the outcome of SCD and health-related quality of life (HRQoL) in adult patients.

Methods

In this longitudinal study, we recruited and prospectively followed 62 adults with SCD (aged ≥18 years) for a median of 93 months. At entry and follow-up, patients provided medical and dietary history, had a physical examination and anthropometric measurements, assessed protein-energy intake, measurement of micronutrient levels, estimation of SCD severity score, and determination of the HRQoL (SF-26v2). The study outcome was a composite of hospitalization due to SCD crises or death.

Results

At baseline, 42 (67.74%) patients had macro and, or micro-undernutrition (Group A), and 20 (32.26%) were well nourished. (Group B). The BMI and most anthropometric measurements were significantly lower in SCD patients compared to control subjects. Seventy percent of SCD patients had vitamin D, vitamin B12, and zinc deficiencies. Thirty-six under-nourished patients (86%) had gastrointestinal disorders. During follow-up, 46 patients (74.19%) developed one or more vaso-occlusive pain crises or other SCD related complications that required hospitalization. Significant differences in most SF-36v2 domains existed between well-nourished and undernourished SCD patients. Protein-energy and micronutrient deficiencies were independent predictors of severe SCD and mortality. Correction of undernutrition and hydroxyurea therapy improved SCD severity scores and HRQoL.

Conclusions

Patients with sickle cell disease have various degrees of macro and micro deficiencies, which increase SCD severity and hospitalizations and reduce the health-related quality of life. Early diagnosis and prompt correction of macro and micronutrient deficiencies need to be incorporated in the standard of care of SCD patients to improve the disease outcomes.

The effect of air-pollution and weather exposure on mortality and hospital admission and implications for further research: A systematic scoping review

BACKGROUND

Air-pollution and weather exposure beyond certain thresholds have serious effects on public health. Yet, there is lack of information on wider aspects including the role of some effect modifiers and the interaction between air-pollution and weather. This article aims at a comprehensive review and narrative summary of literature on the association of air-pollution and weather with mortality and hospital admissions; and to highlight literature gaps that require further research.

METHODS

We conducted a scoping literature review. The search on two databases (PubMed and Web-of-Science) from 2012 to 2020 using three conceptual categories of "environmental factors", "health outcomes", and "Geographical region" revealed a total of 951 records. The narrative synthesis included all original studies with time-series, cohort, or case cross-over design; with ambient air-pollution and/or weather exposure; and mortality and/or hospital admission outcomes.

RESULTS

The final review included 112 articles from which 70 involved mortality, 30 hospital admission, and 12 studies included both outcomes. Air-pollution was shown to act consistently as risk factor for all-causes, cardiovascular, respiratory, cerebrovascular and cancer mortality and hospital admissions. Hot and cold temperature was a risk factor for wide range of cardiovascular, respiratory, and psychiatric illness; yet, in few studies, the increase in temperature reduced the risk of hospital admissions for pulmonary embolism, angina pectoris, chest, and ischemic heart diseases. The role of effect modification in the included studies was investigated in terms of gender, age, and season but not in terms of ethnicity.

CONCLUSION

Air-pollution and weather exposure beyond certain thresholds affect human health negatively. Effect modification of important socio-demographics such as ethnicity and the interaction between air-pollution and weather is often missed in the literature. Our findings highlight the need of further research in the area of health behaviour and mortality in relation to air-pollution and weather, to guide effective environmental health precautionary measures planning.

The Gut Microbiome Regulates Psychological-Stress-Induced Inflammation

Psychological stress has adverse effects on various human diseases, including those of the cardiovascular system. However, the mechanisms by which stress influences disease activity remain unclear. Here, using vaso-occlusive episodes (VOEs) of sickle cell disease as a vascular disease model, we show that stress promotes VOEs by eliciting a glucocorticoid hormonal response that augments gut permeability, leading to microbiota-dependent interleukin-17A (IL-17A) secretion from T helper 17 (Th17) cells of the lamina propria, followed by the expansion of the circulating pool of aged neutrophils that trigger VOEs. We identify segmented filamentous bacteria as the commensal essential for the stress-induced expansion of aged neutrophils that enhance VOEs in mice. Importantly, the inhibition of glucocorticoids synthesis, blockade of IL-17A, or depletion of the Th17 cell-inducing gut microbiota markedly reduces stress-induced VOEs. These results offer potential therapeutic targets to limit the impact of psychological stress on acute vascular occlusion.

Unexpected association between increased levels of ambient carbon monoxide and reduced daily outpatient visits for vaginitis: A hospital-based study

Carbon monoxide (CO) is a well-known "toxic gas". It represents a toxic inhalation hazard at high concentration and is commonly found in polluted air. However, a series of recent studies have suggested that low concentration of CO can also produce protective functions. This study was performed to investigate the association between ambient CO exposure and vaginitis outpatient visits. Daily baseline outpatient data of vaginitis from January 1, 2013 to December 31, 2015 were obtained from Xi'an, a heavily-polluted metropolis in China. The over-dispersed Poisson generalized additive model was applied to discover the relations between short-term ambient CO exposure and the number of vaginitis outpatient visits by adjusting day of the week and weather conditions. A total of 16,825 outpatient hospital visits for vaginitis were recorded. The mean daily concentration of carbon monoxide (CO) was well below Chinese and WHO guidelines. During the study period, increased levels of ambient CO was associated with reduced outpatient-visits through concurrent to lag 5 days, and the most significant association was evidenced at lag 05. A 0.1 mg/m³ increase in daily average CO at lag 05 corresponded to -1.25% (95%CI: -1.85%, -0.65%) change in outpatient-visits for vaginitis. Moreover, the association was more significant in those women aged 20-29 years. After adjustment for PM₁₀, PM_2.5, SO₂, and NO₂, and O₃, the negative associations of CO with vaginitis kept significant, suggesting relative stability of effect estimates. In summary, this is the first evidence that increased ambient CO exposure can be related to reduced daily outpatient visits for vaginitis. The results of our study may not only help to establish more comprehensive understanding of the health effects of ambient air on vaginitis and other gynecological diseases, but also provide a clue to new potential interventions.

Ambient air pollution and sickle cell disease-related emergency department visits in Atlanta, GA

BACKGROUND

Sickle cell disease (SCD) is an inherited, autosomal recessive blood disorder, among the most prevalent genetic diseases, globally. While the genetic and hemolytic dynamics of SCD have been well-characterized, the etiology of SCD-related pathophysiological processes is unclear. Although limited, observational evidence suggests that environmental factors, including urban air pollution, may play a role.

OBJECTIVES

We assessed whether daily ambient air pollution concentrations are associated with corresponding emergency department (ED) visit counts for acute SCD exacerbations in Atlanta, Georgia, during a 9-year (2005-2013) period. We also examined heterogeneity in response by age and sex.

METHODS

ED visit data were from 41 hospitals in the 20-county Atlanta, GA area. Associations between daily air pollution levels for 8 urban air pollutants and counts of SCD related ED visits were estimated using Poisson generalized linear models.

RESULTS

We observed positive associations between pollutants generally indicative of traffic emissions and corresponding SCD ED visits [e.g., rate ratio of 1.022 (95% CI: 1.002, 1.043) per interquartile range increase in carbon monoxide]. Age stratified analyses indicated stronger associations with traffic pollutants among children (0-18 years), as compared to older age strata. Associations involving other pollutants, including ozone and particulate matter and for models of individuals >18 years old, were consistent a null hypothesis of no association.

DISCUSSION

This analysis represents the first North American study to examine acute risk among individuals with SCD to urban air pollution and provide evidence of urban air pollution, especially from traffic sources, as a trigger for acute exacerbations. These findings are consistent with a hypothesis that biological pathways, including several centrally associated with oxidative stress, may contribute towards enhanced susceptibility in individuals with SCD.

Identifying Clinical and Research Priorities in Sickle Cell Lung Disease. An Official American Thoracic Society Workshop Report

Background: Pulmonary complications of sickle cell disease (SCD) are diverse and encompass acute and chronic disease. The understanding of the natural history of pulmonary complications of SCD is limited, no specific therapies exist, and these complications are a primary cause of morbidity and mortality.Methods: We gathered a multidisciplinary group of pediatric and adult hematologists, pulmonologists, and emergency medicine physicians with expertise in SCD-related lung disease along with an SCD patient advocate for an American Thoracic Society-sponsored workshop to review the literature and identify key unanswered clinical and research questions. Participants were divided into four subcommittees on the basis of expertise: 1) acute chest syndrome, 2) lower airways disease and pulmonary function, 3) sleep-disordered breathing and hypoxia, and 4) pulmonary vascular complications of SCD. Before the workshop, a comprehensive literature review of each subtopic was conducted. Clinically important questions were developed after literature review and were finalized by group discussion and consensus.Results: Current knowledge is based on small, predominantly observational studies, few multicenter longitudinal studies, and even fewer high-quality interventional trials specifically targeting the pulmonary complications of SCD. Each subcommittee identified the three or four most important unanswered questions in their topic area for researchers to direct the next steps of clinical investigation.Conclusions: Important and clinically relevant questions regarding sickle cell lung disease remain unanswered. High-quality, multicenter, longitudinal studies and randomized clinical trials designed and implemented by teams of multidisciplinary clinician-investigators are needed to improve the care of individuals with SCD.

Air Drep-A Retrospective Study Evaluating the Influence of Weather Conditions and Viral Epidemics on Vaso-Occlusive Crises in Patients with Sickle Cell Disease Living in French Guiana

(1) Objectives: French Guiana is the French territory most affected by sickle cell disease (SCD). This study investigates the associations between different environmental factors relative to climate, infectious outbreaks, and emergency visits or weekly hospital admissions for vaso-occlusive crisis (VOC). The identification of risk factors would lead to better patient care and patient management, and more targeted prevention and therapeutic education for patients with SCD in French Guiana. (2) Methods: This study was performed using data collected from the medicalized information system and emergency medical records of Cayenne General Hospital, between 1 January 2010 and 31 December 2016. ARIMA models were used to investigate the potential impact of weather conditions and flu epidemics on VOC occurrence. (3) Results: During the study period, 1739 emergency visits were recorded among 384 patients, of which 856 (49.2%) resulted in hospitalization, 811 (46.6%) resulted in hospital discharge, and 72 (4.2%) in another orientation. Decreased temperature and decreased humidity were both independent factors associated with an increase of VOC cases (p = 0.0128 and p = 0.0004, respectively). When studying severe VOC (leading to hospitalization, with or without prior emergency visit), 2104 hospital admissions were recorded for 326 patients. The only factor associated with severe VOC, in the multivariate analysis, was flu epidemics (p = 0.0148). (4) Conclusions: This study shows a link between climate, flu epidemics, and VOC in French Guiana. Patient’s awareness of risks related to climate and flu epidemics should be encouraged, as home prevention measures can help avoid painful crises. Moreover, physicians should encourage patients to get immunized for influenza every year.

Sickle cell disease: Clinical presentation and management of a global health challenge

Sickle cell disease is an autosomal recessive, multisystem disorder, characterised by chronic haemolytic anaemia, painful episodes of vaso-occlusion, progressive organ failure and a reduced life expectancy. Sickle cell disease is the most common monogenetic disease, with millions affected worldwide. In well-resourced countries, comprehensive care programs have increased life expectancy of sickle cell disease patients, with almost all infants surviving into adulthood. Therapeutic options for sickle cell disease patients are however, still scarce. Predictors of sickle cell disease severity and a better understanding of pathophysiology and (epi)genetic modifiers are warranted and could lead to more precise management and treatment. This review provides an extensive summary of the pathophysiology and management of sickle cell disease and encompasses the characteristics, complications and current and future treatment options of the disease.

A review of the experimental evidence on the toxicokinetics of carbon monoxide: the potential role of pathophysiology among susceptible groups

BACKGROUND

Acute high level carbon monoxide (CO) exposure can cause immediate cardio-respiratory arrest in anyone, but the effects of lower level exposures in susceptible persons are less well known. The percentage of CO-bound hemoglobin in blood (carboxyhemoglobin; COHb) is a marker of exposure and potential health outcomes. Indoor air quality guidelines developed by the World Health Organization and Health Canada, among others, are set so that CO exposure does not lead to COHb levels above 2.0%, a target based on experimental evidence on toxicodynamic relationships between COHb and cardiac performance among persons with cardiovascular disease (CVD). The guidelines do not consider the role of pathophysiological influences on toxicokinetic relationships. Physiological deficits that contribute to increased CO uptake, decreased CO elimination, and increased COHb formation can alter relationships between CO exposures and resulting COHb levels, and consequently, the severity of outcomes. Following three fatalities attributed to CO in a long-term care facility (LTCF), we queried whether pathologies other than CVD could alter CO-COHb relationships. Our primary objective was to inform susceptibility-specific modeling that accounts for physiological deficits that may alter CO-COHb relationships, ultimately to better inform CO management in LTCFs.

METHODS

We reviewed experimental studies investigating relationships between CO, COHb, and outcomes related to health or physiological outcomes among healthy persons, persons with CVD, and six additional physiologically susceptible groups considered relevant to LTCF residents: persons with chronic obstructive pulmonary disease (COPD), anemia, cerebrovascular disease (CBD), heart failure, multiple co-morbidities, and persons of older age (≥ 60 years).

RESULTS

We identified 54 studies published since 1946. Six studies investigated toxicokinetics among healthy persons, and the remaining investigated toxicodynamics, mainly among healthy persons and persons with CVD. We identified one study each of CO dynamics in persons with COPD, anemia and persons of older age, and no studies of persons with CBD, heart failure, or multiple co-morbidities. Considerable heterogeneity existed for exposure scenarios and outcomes investigated.

CONCLUSIONS

Limited experimental human evidence on the effects of physiological deficits relevant to CO kinetics exists to support indoor air CO guidelines. Both experimentation and modeling are needed to assess how physiological deficits influence the CO-COHb relationship, particularly at sub-acute exposures relevant to indoor environments. Such evidence would better inform indoor air quality guidelines and CO management in indoor settings where susceptible groups are housed.

Socio-environmental exposures and health outcomes among persons with sickle cell disease

There is much variability in the expression of sickle cell disease (SCD) and recent works suggest that environmental and social factors may also influence this variability. This paper aims to use geographic information systems technology to examine the association between socio-environmental exposures and health outcomes in all persons who have attended or currently attend the Sickle Cell Unit in Jamaica. Rural patients presented for clinical care at older ages and had less annual visits to clinic. Persons travelled relatively long distances to seek SCD care and those travelling longer had less health maintenance visits. Urban patients had a higher prevalence of significant pain crises (69.4% vs. 55.8%, p value<0.001) and respiratory events (21.2% vs. 14%, p value<0.001). Prevalence of leg ulcers did not vary between rural and urban patients but was higher in males than in females. Females also had lower odds of having respiratory events but there was no sex difference in history of painful crises. Persons with more severe genotypes lived in higher poverty and travelled longer for healthcare services. Persons in areas with higher annual rainfall, higher mean temperatures and living farther from factories had less painful crises and respiratory events. The paper highlights a need for better access to healthcare services for Jamaicans with SCD especially in rural areas of the island. It also reports interesting associations between environmental climatic exposures and health outcomes.

Associations between environmental factors and hospital admissions for sickle cell disease

Sickle cell disease is an increasing global health burden. This inherited disease is characterized by a remarkable phenotypic heterogeneity, which can only partly be explained by genetic factors. Environmental factors are likely to play an important role but studies of their impact on disease severity are limited and their results are often inconsistent. This study investigated associations between a range of environmental factors and hospital admissions of young patients with sickle cell disease in London and in Paris between 2008 and 2012. Specific analyses were conducted for subgroups of patients with different genotypes and for the main reasons for admissions. Generalized additive models and distributed lag non-linear models were used to assess the magnitude of the associations and to calculate relative risks. Some environmental factors significantly influence the numbers of hospital admissions of children with sickle cell disease, although the associations identified are complicated. Our study suggests that meteorological factors are more likely to be associated with hospital admissions for sickle cell disease than air pollutants. It confirms previous reports of risks associated with wind speed (risk ratio: 1.06/standard deviation; 95% confidence interval: 1.00–1.12) and also with rainfall (1.06/standard deviation; 95% confidence interval: 1.01–1.12). Maximum atmospheric pressure was found to be a protective factor (0.93/standard deviation; 95% confidence interval: 0.88–0.99). Weak or no associations were found with temperature. Divergent associations were identified for different genotypes or reasons for admissions, which could partly explain the lack of consistency in earlier studies. Advice to patients with sickle cell disease usually includes avoiding a range of environmental conditions that are believed to trigger acute complications, including extreme temperatures and high altitudes. Scientific evidence to support such advice is limited and sometimes confusing. This study shows that environmental factors do explain some of the variations in rates of admission to hospital with acute symptoms in sickle cell disease, but the associations are complex, and likely to be specific to different environments and the individual’s exposure to them. Furthermore, this study highlights the need for prospective studies with large numbers of patients and standardized protocols across Europe.

Secondhand smoke is associated with more frequent hospitalizations in children with sickle cell disease

Tobacco smoke exposure has been associated with more frequent hospitalizations in children with sickle cell disease (SCD), but previous studies have not quantified the exposure by objective methods. We enrolled 50 children and young adults with SCD in a retrospective and prospective cohort study and quantified tobacco smoke exposure by objective (salivary cotinine) and survey measures. We used a multivariable negative binomial regression model to evaluate the association between salivary cotinine and hospital admissions. Forty-five percent (22/49) of participants had significant elevation of salivary cotinine (≥ 0.5 ng/ml). The incidence risk ratio (IRR) for hospital admission for those with elevated cotinine was 3.7 (95% CI 1.8-8). Those exposed to secondhand smoke but not primary smokers (cotinine between 0.5 and 10 ng/ml) had a similarly increased risk of hospitalization [IRR 4.3 (95% CI 1.8-10)]. We show that an objective measure of tobacco smoke exposure, salivary cotinine, is strongly associated with the rate of hospital admissions in children and young adults with SCD. This association underscores the importance of screening for tobacco smoke exposure in people with SCD. Further investigation is warranted to determine the mechanisms of and to evaluate interventions to decrease tobacco smoke exposure.

Environmental determinants of severity in sickle cell disease

Sickle cell disease causes acute and chronic illness, and median life expectancy is reduced by at least 30 years in all countries, with greater reductions in low-income countries. There is a wide spectrum of severity, with some patients having no symptoms and others suffering frequent, life-changing complications. Much of this variability is unexplained, despite increasingly sophisticated genetic studies. Environmental factors, including climate, air quality, socio-economics, exercise and infection, are likely to be important, as demonstrated by the stark differences in outcomes between patients in Africa and USA/Europe. The effects of weather vary with geography, although most studies show that exposure to cold or wind increases hospital attendance with acute pain. Most of the different air pollutants are closely intercorrelated, and increasing overall levels seem to correlate with increased hospital attendance, although higher concentrations of atmospheric carbon monoxide may offer some benefit for patients with sickle cell disease. Exercise causes some adverse physiological changes, although this may be off-set by improvements in cardiovascular health. Most sickle cell disease patients live in low-income countries and socioeconomic factors are undoubtedly important, but little studied beyond documenting that sickle cell disease is associated with decreases in some measures of social status. Infections cause many of the differences in outcomes seen across the world, but again these effects are relatively poorly understood. All the above factors are likely to account for much of the pathology and variability of sickle cell disease, and large prospective studies are needed to understand these effects better.

Positron Emission Tomography With 18F-Fluorodeoxyglucose in Patients With Sickle Cell Acute Chest Syndrome

The acute chest syndrome (ACS) is the main cause of mortality among adult patients with sickle cell disease (SCD). Its pathophysiology is still unclear. Using positron emission tomography (PET) with F-fluorodeoxyglucose [18F-fluorodeoxyglucose (F-FDG)], we explored the relationship between regional lung density and lung metabolism, as a reflection of lung neutrophilic infiltration during ACS.Patients were prospectively enrolled in a single-center study. Dual modality chest PET/computed tomography (CT) scans were performed, with F-FDG emission scans for quantification of regional F-FDG uptake and CT scans with radiocontrast agent to check for pulmonary artery thrombosis. Regional lung F-FDG uptake was quantified in ACS patients and in SCD patients without ACS (SCD non-ACS controls). Maximal (SUVmax) and mean (SUVmean) standardized uptake values were computed.Seventeen patients with ACS (mean age 28.3 ± 6.4 years) were included. None died nor required invasive mechanical ventilation. The main lung opacity on CT scans was lower lobe consolidation. Lungs of patients with ACS exhibited higher SUVmax than those of SCD non-ACS controls (2.5 [2.1-2.9] vs 0.8 [0.6-1.0]; P < 0.0001). Regional SUVmax and SUVmean was higher in lower than in upper lobes of ACS patients (P < 0.001) with a significant correlation between lung density and SUVmax (R = 0.78). SUVmean was higher in upper lobes of ACS patients than in lungs of SCD non-ACS controls (P < 0.001). Patients with SUVmax >2.5 had longer intensive care unit (ICU) stay than others (7 [6-11] vs 4 [3-6] days; P = 0.016).Lungs of patients with ACS exhibited higher F-FDG uptake than SCD non-ACS controls. Lung apices had normal aeration and lower F-FDG uptake than lung bases, but higher F-FDG uptake than lungs of SCD non-ACS controls. Patients with higher lung F-FDG uptake had longer ICU stay than others.