Exposure of children with cystic fibrosis to environmental tobacco smoke

Genomic analysis of the liverpool epidemic strain of pseudomonas aeruginosa infecting persons with cystic fibrosis reveals likely Canadian origins

INTRODUCTION

The Liverpool Epidemic Strain (LES) of Pseudomonas aeruginosa is one of several known strains to be transmissible between persons with cystic fibrosis (CF) (pwCF) and the only known strain to have infected large proportions of CF populations on two continents. Despite its prevalence, efforts to understand its spread have proven elusive.

METHODS

We leveraged a prospective collection of P. aeruginosa isolates from pwCF attending the Southern Alberta Adult CF clinic from 1986 to 2020 to identify all individuals with LES infection. LES isolates collected every 1-2 years from each pwCF were sequenced and compared with 171 published LES genomes by phylogenetic analysis.

RESULTS

Of 395 pwCF screened, ten pwCF infected with the LES were identified, from whom 46 LES isolates were sequenced. The earliest LES isolate was recovered in 1986, ∼2 years earlier than the previously oldest published LES isolate recovered in the UK. Phylogenetic analysis identified a diverse set of isolates at the root of the LES phylogeny that formed four clades, one of which gave rise to a "classic LES" clade. Canadian isolates formed a paraphyletic group that included the root of this clade and out of which the UK LES clade emerged. We estimated the date of the most recent common ancestor (MRCA) of the UK LES clade as 1977.

CONCLUSIONS

Our study provides genomic evidence in support of a silent epidemic of LES infection occurring in the late 1970s among pwCF first originating in Canada and being spread to the UK, where transmission markedly accelerated.

Secondhand vape exposure regulation of CFTR and immune function in cystic fibrosis

Secondhand smoke exposure (SHSe) is a public health threat for people with cystic fibrosis (CF) and other lung diseases. Primary smoking reduces CF transmembrane conductance regulator (CFTR) channel function, the causative defect in CF. We reported that SHSe worsens respiratory and nutritional outcomes in CF by disrupting immune responses and metabolic signaling. Recently, electronic cigarette (e-cigs) usage by caregivers and peers has increased rapidly, causing new secondhand e-cig vape exposures. Primary vaping is associated with immunologic deficits in healthy people, but it is unknown whether e-cigs similarly impacts CF immune function or how it differs from SHSe. Human CF and non-CF blood monocyte-derived macrophages (MDMs) and bronchial epithelial cells (HBECs) were exposed to flavored and unflavored e-cigs. The effect of e-cigs on CFTR expression and function, bacterial killing, cytokine signaling, lipid mediators, and metabolism was measured during treatment with CFTR modulators. E-cigs decreased CFTR expression and function in CF and non-CF MDMs and negated CFTR functional restoration by elexacaftor/tezacaftor/ivacaftor (ETI). E-cigs also negated the restoration of anti-inflammatory PGD2 expression in CF MDMs treated with ETI compared with controls. Flavored but not unflavored e-cigs increased proinflammatory cytokine expression in CF MDMs and e-cigs promoted glycolytic metabolism. E-cigs did not impact bacterial killing. Overall, HBECs were less impacted by e-cigs compared with MDMs. E-cigs reduced macrophage CFTR expression and hindered functional CFTR restoration by CFTR modulators, promoting a glycolytic, proinflammatory state. E-cigs are an emerging public health threat that may limit the efficacy of CFTR modulators in people with CF.NEW & NOTEWORTHY New research reveals that e-cigarettes pose a serious health risk for individuals with cystic fibrosis (CF). Exposure to electronic cigarette (e-cig) vapors decreases CF transmembrane conductance regulator (CFTR) function and undermines the effectiveness of CFTR modulators, potentially worsening inflammation and metabolic responses. This highlights an urgent need for awareness around e-cig use, especially among caregivers and peers of those with CF. E-cigarettes may further complicate the management of this chronic lung disease.

Socioeconomic determinants of respiratory health in patients with cystic fibrosis: implications for treatment strategies

INTRODUCTION

Great variation exists in the progression and outcomes of cystic fibrosis (CF) lung disease, due to both genetic and environmental influences. Social determinants mediate environmental exposures and treatment success; people with CF from socioeconomically disadvantaged backgrounds have worse health and die younger than those in more advantaged positions.

AREAS COVERED

This paper reviews the literature on the mechanisms that are responsible for generating and sustaining disparities in CF health, and the ways by which social determinants translate into health advantages or disadvantages in people with CF. The authors make recommendations for addressing social risk factors in CF clinical practice.

EXPERT OPINION

Socioeconomic factors are not dichotomous and their impact is felt at every step of the social ladder. CF care programs need to adopt a systematic protocol to screen for health-related social risk factors, and then connect patients to available resources to meet individual needs. Considerations such as daycare, schooling options, living and working conditions, and opportunities for physical exercise and recreation as well as promotion of self-efficacy are often overlooked. In addition, advocacy for changes in public policies on health insurance, environmental regulations, social welfare, and education would all help address the root causes of CF health inequities.

The Impact of Air Pollution on the Course of Cystic Fibrosis: A Review

Cystic fibrosis (CF) is a lethal and widespread autosomal recessive disorder affecting over 80,000 people worldwide. It is caused by mutations of the CFTR gene, which encodes an epithelial anion channel. CF is characterized by a great phenotypic variability which is currently not fully understood. Although CF is genetically determined, the course of the disease might also depend on multiple other factors. Air pollution, whose effects on health and contribution to respiratory diseases are well established, is one environmental factor suspected to modulate the disease severity and influence the lung phenotype of CF patients. This is of particular interest as pulmonary failure is the primary cause of death in CF. The present review discusses current knowledge on the impact of air pollution on CF pathogenesis and aims to explore the underlying cellular and biological mechanisms involved in these effects.

CFTR bearing variant p.Phe312del exhibits function inconsistent with phenotype and negligible response to ivacaftor

The chloride channel dysfunction caused by deleterious cystic fibrosis transmembrane conductance regulator (CFTR) variants generally correlates with severity of cystic fibrosis (CF). However, 3 adults bearing the common severe variant p.Phe508del (legacy: F508del) and a deletion variant in an ivacaftor binding region of CFTR (p.Phe312del; legacy: F312del) manifested only elevated sweat chloride concentration (sw[Cl-]; 87-105 mEq/L). A database review of 25 individuals with F312del and a CF-causing variant revealed elevated sw[Cl-] (75-123 mEq/L) and variable CF features. F312del occurs at a higher-than-expected frequency in the general population, confirming that individuals with F312del and a CF-causing variant do not consistently develop overt CF features. In primary nasal cells, CFTR bearing F312del and F508del generated substantial chloride transport (66.0% ± 4.5% of WT-CFTR) but did not respond to ivacaftor. Single-channel analysis demonstrated that F312del did not affect current flow through CFTR, minimally altered gating, and ablated the ivacaftor response. When expressed stably in CF bronchial epithelial (CFBE41o-) cells, F312del-CFTR demonstrated residual function (50.9% ± 3.3% WT-CFTR) and a subtle decrease in forskolin response compared with WT-CFTR. F312del provides an exception to the established correlation between CFTR chloride transport and CF phenotype and informs our molecular understanding of ivacaftor response.

Predicting Substance Use from Religiosity/Spirituality in Individuals with Cystic Fibrosis

Religiosity and spirituality predict lower alcohol and other substance use in community samples of adolescents and adults. However, the roles of religiosity and spirituality in substance use have not been examined in individuals with cystic fibrosis (CF). Adults with CF (n = 123) completed measures of spirituality, religiosity, and substance use. Clinical measures of illness severity (e.g., BMI and  %FEV₁) were obtained from participants' medical records. Substance use rates for alcohol, tobacco, and marijuana were lower in this sample than those seen in the general population. Of the measured BMMRS subscales, spiritual experiences and religious commitment were significant predictors of lower alcohol use. These results suggest that personal factors of religiosity and spirituality are more important for substance use in adults with CF than participation in religious service and events or adoption of religious practices.

Metabolomics profiling of tobacco exposure in children with cystic fibrosis

BACKGROUND

Inflammation is integral to early disease progression in children with CF. The effect of modifiable environmental factors on infection and inflammation in persons with CF is poorly understood. Our prior studies determined that secondhand smoke exposure (SHSe) is highly prevalent in young children with CF. SHSe is associated with increased inflammation, heightened bacterial burden, and worsened clinical outcomes. However, the specific metabolite and signaling pathways that regulate responses to SHSe in CF are relatively unknown.

METHODS

High-resolution metabolomics was performed on plasma samples from infants (n = 25) and children (n = 40) with CF compared to non-CF controls (n = 15). CF groups were stratified according to infant or child age and SHSe status.

RESULTS

Global metabolomic profiles segregated by age and SHSe status. SHSe in CF was associated with changes in pathways related to steroid biosynthesis, fatty acid metabolism, cysteine metabolism, and oxidative stress. CF infants with SHSe demonstrated enrichment for altered metabolite localization to the small intestine, liver, and striatum. CF children with SHSe demonstrated metabolite enrichment for organs/tissues associated with oxidative stress including mitochondria, peroxisomes, and the endoplasmic reticulum. In a confirmatory analysis, SHSe was associated with changes in biomarkers of oxidative stress and cellular adhesion including MMP-9, MPO, and ICAM-1.

CONCLUSIONS

SHSe in young children and infants with CF is associated with altered global metabolomics profiles and specific biochemical pathways, including enhanced oxidative stress. SHSe remains an important but understudied modifiable variable in early CF disease.

Influences of environmental exposures on individuals living with cystic fibrosis

INTRODUCTION

Natural, social, and constructed environments play a critical role in the development and exacerbation of respiratory diseases. However, less is known regarding the influence of these environmental/community risk factors on the health of individuals living with cystic fibrosis (CF), compared to other pulmonary disorders.

AREAS COVERED

Here, we review current knowledge of environmental exposures related to CF, which suggests that environmental/community risk factors do interact with the respiratory tract to affect outcomes. Studies discussed in this review were identified in PubMed between March 2019 and March 2020. Although the limited data available do not suggest that avoiding potentially detrimental exposures other than secondhand smoke could improve outcomes, additional research incorporating novel markers of environmental exposures and community characteristics obtained at localized levels is needed.

EXPERT OPINION

As we outline, some environmental exposures and community characteristics are modifiable; if not by the individual, then by policy. We recommend a variety of strategies to advance understanding of environmental influences on CF disease progression.

The association between environmental tobacco smoke exposure and childhood respiratory disease: a review

INTRODUCTION

Childhood respiratory illness is a major cause of morbidity and mortality particularly in low and middle-income countries. Environmental tobacco smoke (ETS) exposure is a recognised risk factor for both acute and chronic respiratory illness. Areas covered: The aim of this paper was to review the epidemiology of ETS exposure and impact on respiratory health in children. We conducted a search of 3 electronic databases of publications on ETS and childhood respiratory illness from 1990-2015. Key findings were that up to 70% of children are exposed to ETS globally, but under-reporting may mask the true prevalence. Maternal smoking and ETS exposure influence infant lung development and are associated with childhood upper and lower respiratory tract infection, wheezing or asthma. Further, exposure to ETS is associated with more severe respiratory disease. ETS exposure reduces lung function early in life, establishing an increased lifelong risk of poor lung health. Expert commentary: Urgent and effective strategies are needed to decrease ETS exposure in young children to improve child and long-term lung health in adults especially in low and middle income countries where ETS exposure is increasing.

Socioeconomic Status, Smoke Exposure, and Health Outcomes in Young Children With Cystic Fibrosis

BACKGROUND

Lower socioeconomic status (SES) and environmental tobacco smoke (ETS) exposure are both associated with poorer disease outcomes in cystic fibrosis (CF), and children with low SES are disproportionately exposed to ETS. We analyzed a large cohort of young children with CF to distinguish the impact of SES and ETS on clinical outcomes.

METHODS

The Early Pseudomonas Infection Control Observational study enrolled Pseudomonas-negative young children with CF <13 years of age. An enrollment survey assessed SES and ETS exposures. Forced expiratory volume in 1 second (FEV₁), crackles and wheezes, and weight-for-age percentile were assessed at each clinical encounter over at least 4 years. Repeated measures analyses estimated the association of SES and ETS exposures with longitudinal clinical outcomes, adjusting for confounders.

RESULTS

Of 1797 participants, 1375 were eligible for analysis. Maternal education was high school or less in 28.1%, 26.8% had household income <$40 000, and 43.8% had Medicaid or no insurance. Maternal smoking after birth was present in 24.8%, more prevalent in household with low SES. In separate models, lower SES and ETS exposure were significantly associated with lower FEV₁% predicted, presence of crackles or wheezes, and lower weight percentile. In combined models, effect estimates for SES changed minimally after adjustment for ETS exposures, whereas estimates for ETS exposures were attenuated after adjusting for SES.

CONCLUSIONS

ETS exposure was disproportionately high in low SES families in this cohort of children with CF. Lower SES and ETS exposure had independent adverse effects on pulmonary and nutritional outcomes. Estimated effect of SES on FEV₁ decreased minimally after ETS adjustment, suggesting health disparity risks independent of ETS exposure.

Respiratory pathogens mediate the association between lung function and temperature in cystic fibrosis

INTRODUCTION

Mean annual ambient temperature is a replicated environmental modifier of cystic fibrosis (CF) lung disease with warmer temperatures being associated with lower lung function. The mechanism of this relationship is not completely understood. However, Pseudomonas aeruginosa, a pathogen that infects the lungs of CF individuals and decreases lung function, also has a higher prevalence in individuals living in warmer climates. We therefore investigated the extent to which respiratory pathogens mediated the association between temperature and lung function.

METHODS

Thirteen respiratory pathogens observed on CF respiratory cultures were assessed in multistep fashion using clustered linear and logistic regression to determine if any mediated the association between temperature and lung function. Analysis was performed in the CF Twin-Sibling Study (n=1730; primary population); key findings were then evaluated in the U.S. CF Foundation Data Registry (n=15,174; replication population).

RESULTS

In the primary population, three respiratory pathogens (P. aeruginosa, mucoid P. aeruginosa, and methicillin-resistant Staphylococcus aureus) mediated the association between temperature and lung function. P. aeruginosa accounted for 19% of the association (p=0.003), mucoid P. aeruginosa for 31% (p=0.001), and MRSA for 13% (p=0.023). The same three pathogens mediated association in the replication population (7%, p<0.001; 7%, p=0.002; and 4%, (p=0.002), respectively).

CONCLUSIONS

Three important respiratory pathogens in CF mediate the association between lower lung function and warmer temperatures. These findings have implications for understanding regional variations in clinical outcomes, and interpreting results of epidemiologic studies and clinical trials that encompass regions with different ambient temperatures.

The Impact of Secondhand Smoke Exposure on Children with Cystic Fibrosis: A Review

Secondhand smoke exposure (SHSe) has multiple adverse effects on lung function and growth, nutrition, and immune function in children; it is increasingly being recognized as an important modifier of disease severity for children with chronic diseases such as cystic fibrosis (CF). This review examines what is known regarding the prevalence of SHSe in CF, with the majority of reviewed studies utilizing parental-reporting of SHSe without an objective biomarker of exposure. A wide range of SHSe is reported in children with CF, but under-reporting is common in studies involving both reported and measured SHSe. Additionally, the impact of SHSe on respiratory and nutritional health is discussed, with potential decreases in long-term lung function, linear growth, and weight gain noted in CF children with SHSe. Immunologic function in children with CF and SHSe remains unknown. The impact of SHSe on cystic fibrosis transmembrane conductance regulator (CFTR) function is also examined, as reduced CFTR function may be a pathophysiologic consequence of SHSe in CF and could modulate therapeutic interventions. Finally, potential interventions for ongoing SHSe are delineated along with recommended future areas of study.

Early Childhood Risk Factors for Decreased FEV1 at Age Six to Seven Years in Young Children with Cystic Fibrosis

RATIONALE

There are limited objective measures of the severity of lung disease before children are able to routinely perform spirometry, generally at age 6 years. Identifying risk factors for reduced lung function at age 6 provides opportunities to intervene and slow the progression of cystic fibrosis (CF) lung disease.

OBJECTIVES

To evaluate early childhood predictors of lung function at age 6-7 in a large U.S. CF cohort in the current era of widespread early eradication therapy for Pseudomonas aeruginosa (P. aeruginosa).

METHODS

Participants were children with CF enrolled before age 4 in the Early Pseudomonas Infection Control (EPIC) Observational Study, a multicenter, longitudinal study that enrolled P. aeruginosa-negative children not exceeding 12 years of age. Linear regression was used to estimate the association between potential early childhood risk factors and the best FEV1% predicted at age 6-7 years.

MEASUREMENTS AND MAIN RESULTS

Four hundred and eighty-four children (of 1,797 enrolled in the EPIC Observational Study) met the eligibility criteria for this analysis. Mean (SD) age at enrollment was 2.0 (1.3) years. In a multivariable model adjusted for age at enrollment, the following risk factors were significantly associated with lower mean (95% confidence interval) FEV1% predicted at age 6-7: weight percentile less than 10% during the year of enrollment (-5.3 [-9.1, -1.5]), P. aeruginosa positive during the year of enrollment (-2.8 [-5.7, 0.0]), crackles or wheeze during the year of enrollment (-5.7 [-9.4, -1.9]), mother's education of high school or less (-4.2 [-7.3, -1.2]), and mother smoked during pregnancy (-4.4 [-8.8, 0.1]).

CONCLUSIONS

In this large U.S. cohort, we identified several early childhood risk factors for lower FEV1 at age 6-7 years, most of which are modifiable. Clinical trial registered with www.clinicaltrials.gov (NCT00097773).

Children with Chronic Lung Disease: Facilitating Smoking Cessation for their Caregivers

Through a QI project at a tertiary referral pediatric pulmonary center, our objective was to establish a methodical approach to identify and engage smoking parents of children with chronic lung disease in a smoking cessation program. We hypothesized that smoking caregivers of children with chronic lung disease would be more motivated to enroll in a smoking cessation program when referred from tertiary pediatric pulmonary center. We assessed smoking habits and interest in quitting of parents with surveys. Parents ready to quit within 30 days were referred to the Florida Quitline from clinic. Pulmonary function tests, exacerbations, hospitalizations and need for prednisone or antibiotics were obtained from the patient charts and surveys. Follow-up two to 6 months later assessed the quit rate and child's clinical well-being and lung function. A standard mechanism to identify caregivers who smoked was established by engaging our medical assistants through a prompt in our EMR system. Out of those caregivers who were identified as smokers and accompanied their children to clinic, 52% were interested in a referral to the Florida Quitline. Out of those, only 12% successfully completed the program and ceased to smoke. The Florida Quitline was unable to reach the majority of parents who were referred to them. The majority of those referred to the Ouitline were not successfully contacted or enrolled in the program. The current procedure for referring and enrolling individuals to the Quitline is not effective for our population, but compares to the national average.

Early Life Growth Trajectories in Cystic Fibrosis are Associated with Pulmonary Function at Age 6 Years

OBJECTIVE

To determine whether severity of lung disease at age 6 years is associated with changes in nutritional status before age 6 within individual children with cystic fibrosis (CF).

STUDY DESIGN

Children with CF born between 1994 and 2005 and followed in the CF Foundation Patient Registry from age ≤2 through 7 years were assessed according to changes in annualized weight-for-length (WFL) percentiles between ages 0 and 2 years and body mass index (BMI) percentiles between ages 2 and 6 years. The association between growth trajectories before age 6 and forced expiratory volume in 1 second (FEV1)% predicted at age 6-7 years was evaluated using multivariable linear regression.

RESULTS

A total of 6805 subjects met inclusion criteria. Children with annualized WFL-BMI always >50th percentile (N = 1323 [19%]) had the highest adjusted mean (95% CI) FEV1 at 6-7 years (101.8 [100.1, 103.5]). FEV1 at 6-7 years for children whose WFL-BMI increased >10 percentile points by age 6 years was 98.3 (96.6, 100.0). This was statistically significantly higher than FEV1 for children whose WFL-BMI was stable (94.4 [92.6, 96.2]) or decreased >10 percentile points (92.9 [91.1, 94.8]). Among children whose WFL-BMI increased >10 percentile points, achieving and maintaining WFL-BMI >50th percentile at younger ages was associated with significantly higher FEV1 at 6-7 years.

CONCLUSIONS

Within-patient changes in nutritional status in the first 6 years of life are significantly associated with FEV1 at age 6-7 years. The establishment of a clear relationship between early childhood growth measurements and later lung function suggests that early nutritional interventions may impact on eventual lung health.

Precision Genomic Medicine in Cystic Fibrosis

The successful application of precision genomic medicine requires an understanding of how a person's genome can influence his or her disease phenotype and how medical therapies can provide personalized therapy to one's genotype. In this review, we highlight advances in precision genomic medicine in cystic fibrosis (CF), a classic autosomal recessive genetic disorder. We discuss genotype-phenotype correlations in CF, genetic and environmental modifiers of disease, and pharmacogenetic therapies that target specific genetic mutations thereby addressing the primary defect of cystic fibrosis.

Genetic modifiers and oligogenic inheritance

Despite remarkable progress in the identification of mutations that drive genetic disorders, progress in understanding the effect of genetic background on the penetrance and expressivity of causal alleles has been modest, in part because of the methodological challenges in identifying genetic modifiers. Nonetheless, the progressive discovery of modifier alleles has improved both our interpretative ability and our analytical tools to dissect such phenomena. In this review, we analyze the genetic properties and behaviors of modifiers as derived from studies in patient populations and model organisms and we highlight conceptual and technological tools used to overcome some of the challenges inherent in modifier mapping and cloning. Finally, we discuss how the identification of these modifiers has facilitated the elucidation of biological pathways and holds the potential to improve the clinical predictive value of primary causal mutations and to develop novel drug targets.

Management of pulmonary exacerbations in cystic fibrosis: still an unmet medical need in clinical practice

Pulmonary exacerbation (PEx) is a hallmark of cystic fibrosis. Although several criteria have been proposed for the definition of PEx, no consensus has yet been reached. Very often, many PEx cases go unreported. A standardized and validated definition is needed to reduce variability in clinical practice. The pathophysiology of recurrent episodes remains unclear, and both onset and risk are multifactorial. PEx leads to increased healthcare costs, impaired quality of life and a cycle in which PEx causes loss of lung function, which predisposes to further episodes. The number of episodes affects survival. Although early diagnosis and aggressive treatment are highly recommended, measures to prevent the emergence of new PEx are even more important. In particular, inhaled antibiotics administered under new treatment schedules could play a key role in preventing exacerbations and thus delay decline in lung function and reduce mortality. The primary objective is zero exacerbations.

Detrimental effects of secondhand smoke exposure on infants with cystic fibrosis

RATIONALE

Secondhand smoke (SHS) has deleterious respiratory, immune, and nutritional effects in children, but there is little data regarding the effects of SHS exposure in infants with cystic fibrosis (CF).

METHODS

A retrospective chart review was undertaken from 2008 to 2012 of 75 infants with CF. Growth, lung function, Chest CT imaging, and microbiologic characteristics were compared between 4 and 12 months for SHS and non-SHS exposed patients.

RESULTS

SHS exposed infants with CF had decreased growth between 4 and 12 months compared to non-SHS exposed infants. SHS exposure was associated with increased bronchodilator responsiveness and air trapping, but no other lung function or radiologic differences. SHS exposure was also associated with increased methicillin resistant Staphylococcus aureus (MRSA) and anaerobic growth on respiratory culture. There was no difference in Pseudomonas aeruginosa between groups. There were no differences in antibiotic use or hospitalizations between the groups.

CONCLUSIONS

SHS exposure in CF infants is associated with diminished growth, increased air trapping and bronchodilator responsiveness, and propensity to culture MRSA and facultative anaerobic bacteria, suggesting the need for early, aggressive parental smoking cessation interventions to prevent SHS exposure complications.

Self-reported exercise and longitudinal outcomes in cystic fibrosis: a retrospective cohort study

BACKGROUND

Cystic fibrosis (CF) is characterized by recurrent respiratory infections and progressive lung disease. Whereas exercise may contribute to preserving lung function, its benefit is difficult to ascertain given the selection bias of healthier patients being more predisposed to exercise. Our objective was to examine the role of self-reported exercise with longitudinal lung function and body mass index (BMI) measures in CF.

METHODS

A total of 1038 subjects with CF were recruited through the U.S. CF Twin-Sibling Study. Questionnaires were used to determine exercise habits. Questionnaires, chart review, and U.S. CF Foundation Patient Registry data were used to track outcomes.

RESULTS

Within the study sample 75% of subjects self-reported regular exercise. Exercise was associated with an older age of diagnosis (p = 0.002), older age at the time of ascertainment (p < 0.001), and higher baseline FEV1 (p = 0.001), but not CFTR genotype (p = 0.64) or exocrine pancreatic function (p = 0.19). In adjusted mixed models, exercise was associated with both a reduced decline in FEV1 (p < 0.001) and BMI Z-score (p = 0.001) for adults, but not children aged 10-17 years old.

CONCLUSIONS

In our retrospective study, self-reported exercise was associated with improved longitudinal nutritional and pulmonary outcomes in cystic fibrosis for adults. Although prospective studies are needed to confirm these associations, programs to promote regular exercise among individuals with cystic fibrosis would be beneficial.

Cat and dog exposure and respiratory morbidities in cystic fibrosis

OBJECTIVE

To understand the triggers that may impact respiratory health in cystic fibrosis (CF), including the effects of pets, because environmental factors contribute to one-half of the variation in lung function in patients with CF.

STUDY DESIGN

A total of 703 subjects with CF were recruited through the US CF Twin-Sibling Study. Questionnaires were used to determine the presence/absence of cats and dogs in households with a child with CF. Questionnaires, chart review, and US CF Foundation Patient Registry data were used to track respiratory and infection outcomes.

RESULTS

Within the sample, 47% of subjects reported owning a dog, and 28% reported owning a cat. After adjustment for demographic factors, dog ownership was not associated with any adverse clinical outcomes, and cat ownership was associated an increased risk in developing nasal polyps (aOR 1.66; P = .024) compared with noncat owners. Subjects who owned both cats and dogs were twice as likely to report wheezing compared with other subjects (aOR: 2.01; P = .009). There were no differences in prevalence and age of acquisition for the common CF respiratory pathogens Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus between cat/dog owners and noncat/dog owners.

CONCLUSIONS

Cat ownership was associated with a greater frequency of developing nasal polyps and combined cat-dog ownership was associated with a greater rate of wheezing. Prospective studies are needed to confirm these associations and the potential psychosocial benefits of cat and/or dog ownership.

Ozone is associated with an increased risk of respiratory exacerbations in patients with cystic fibrosis

Background

Tropospheric oxidant pollutants may injure the respiratory tract. Cystic fibrosis (CF) respiratory disease involves significant inflammation and excessive oxidative stress, and exposure to air pollutants can magnify the lung damage. The objective of this study was to investigate the association between the short-term variation in the concentration of air pollutants in metropolitan São Paulo, Brazil, and the occurrence of respiratory exacerbations in children and adolescents with CF.

Methods

A longitudinal panel of repeated measurements was obtained from 103 patients attending the outpatient center of our institution from September 6, 2006 through September 4, 2007. Daily concentrations of inhaled particulate matter, sulfur dioxide, nitrogen dioxide, ozone (O₃), carbon monoxide, and meteorologic variables, such as the minimum temperature and relative humidity, were evaluated. The generalized estimation equation model for binomial distribution was used to assess the impact of these measurements on the occurrence of acute respiratory exacerbations.

Results

In total, 103 patients with CF (median age, 8.9 years) made 408 visits, with a mean ± SD of 4 ± 1.74 visits per patient (range, 2-9). A respiratory disease exacerbation was diagnosed on 142 visits (38.4%). An interquartile range increase in the O₃ concentration (45.62 μg/m³) had a positive, delayed (2 days after exposure) effect on the risk of a respiratory exacerbation (relative risk = 1.86; 95% CI, 1.14-3.02).

Conclusions

This study demonstrates that exposure to short-term air pollution in a large urban center increases the risk of a pulmonary exacerbation in patients with CF.

Genetic influences on cystic fibrosis lung disease severity

Understanding the causes of variation in clinical manifestations of disease should allow for design of new or improved therapeutic strategies to treat the disease. If variation is caused by genetic differences between individuals, identifying the genes involved should present therapeutic targets, either in the proteins encoded by those genes or the pathways in which they function. The technology to identify and genotype the millions of variants present in the human genome has evolved rapidly over the past two decades. Originally only a small number of polymorphisms in a small number of subjects could be studied realistically, but speed and scope have increased nearly as dramatically as cost has decreased, making it feasible to determine genotypes of hundreds of thousands of polymorphisms in thousands of subjects. The use of such genetic technology has been applied to cystic fibrosis (CF) to identify genetic variation that alters the outcome of this single gene disorder. Candidate gene strategies to identify these variants, referred to as “modifier genes,” has yielded several genes that act in pathways known to be important in CF and for these the clinical implications are relatively clear. More recently, whole-genome surveys that probe hundreds of thousands of variants have been carried out and have identified genes and chromosomal regions for which a role in CF is not at all clear. Identification of these genes is exciting, as it provides the possibility for new areas of therapeutic development.

Nongenetic influences on cystic fibrosis outcomes

PURPOSE OF REVIEW

Despite dramatic improvements over the last several decades, tremendous variation exists in cystic fibrosis (CF) health outcomes. Genetic explanations for variations in disease progression are a promising source of information regarding disease biology and pathophysiology, but an understanding of nongenetic factors provides more immediate tools for improving disease outcomes.

RECENT FINDINGS

The clinical course of CF for any individual with CF is determined by the interaction of genetic endowment (including CFTR and modifier genes), the physical environment (including environmental tobacco smoke, outdoor pollution, and pathogenic microorganisms), the sociodemographic, cultural, and family context (which mediates stress, social support, and disease self-management skills), and variations in delivery and acceptance of healthcare treatments. The evidence linking socioeconomic status (SES) with CF outcomes continues to be strong, and appears to be primarily due to associations with environmental and sociocultural stressors and disease-management behaviors rather than barriers in access to healthcare.

SUMMARY

Attempts to eliminate detrimental environmental exposures, improve disease self-management skills, and ensure consistently optimal healthcare practices will likely decrease variations in outcomes including SES-related disparities. Low SES is an important marker of adverse exposures and outcomes which are present throughout the CF population.

Effect of temperature on cystic fibrosis lung disease and infections: a replicated cohort study

Background

Progressive lung disease accounts for the majority of morbidity and mortality observed in cystic fibrosis (CF). Beyond secondhand smoke exposure and socio-economic status, the effect of specific environmental factors on CF lung function is largely unknown.

Methods

Multivariate regression was used to assess correlation between specific environmental factors, the presence of pulmonary pathogens, and variation in lung function using subjects enrolled in the U.S. CF Twin and Sibling Study (CFTSS: n = 1378). Significant associations were tested for replication in the U.S. CF Foundation Patient Registry (CFF: n = 16439), the Australian CF Data Registry (ACFDR: n = 1801), and prospectively ascertained subjects from Australia/New Zealand (ACFBAL: n = 167).

Results

In CFTSS subjects, the presence of Pseudomonas aeruginosa (OR = 1.06 per °F; p<0.001) was associated with warmer annual ambient temperatures. This finding was independently replicated in the CFF (1.02; p<0.001), ACFDR (1.05; p = 0.002), and ACFBAL (1.09; p = 0.003) subjects. Warmer temperatures (−0.34 points per °F; p = 0.005) and public insurance (−6.43 points; p<0.001) were associated with lower lung function in the CFTSS subjects. These findings were replicated in the CFF subjects (temperature: −0.31; p<0.001; insurance: −9.11; p<0.001) and similar in the ACFDR subjects (temperature: −0.23; p = 0.057). The association between temperature and lung function was minimally influenced by P. aeruginosa. Similarly, the association between temperature and P. aeruginosa was largely independent of lung function.

Conclusions

Ambient temperature is associated with prevalence of P. aeruginosa and lung function in four independent samples of CF patients from two continents.

[Survey on passive smoking in children in Agadir]

INTRODUCTION

The aim of the study was to assess children's exposure to tobacco smoke at home, at school and in public places, to study its risks and to educate parents about the dangers of passive smoking.

METHODS

This is a survey conducted in October 2007 among children enrolled in pre-school and primary school in the city of Agadir, Morocco. The data was gathered by a written questionnaire completed by parents at home.

RESULTS

The survey covered 776 children. The response rate to the questionnaires was 88%. The father was a smoker in 28.9% of cases, against 0.7% for the mother. The prevalence of childhood exposure to tobacco was 34.1% at home, 36.4% in public places and 30.1% in schools. Concerning pregnant women, passive smoking and/or active was associated with a significantly increased risk of respiratory distress in newborn babies and hospitalisations in the neonatology department. In infant and child, involuntary inhalation of tobacco smoke involved an increased risk of sudden infant death syndrome and recurrent respiratory symptoms. However, its noxious effects were not found in the case of child asthma and tumour.

CONCLUSION

Passive smoking is a real public health problem and smoking is a dangerous but also a preventable source of pollution.

Association between socioeconomic status, sex, and age at death from cystic fibrosis in England and Wales (1959 to 2008): cross sectional study

OBJECTIVE

To determine the trend in the association between socioeconomic status and sex and median age at death from cystic fibrosis in England and Wales, over the past 50 years.

DESIGN

Series of annual cross sectional studies of all registered deaths with a diagnosis of cystic fibrosis in England and Wales, from 1959 to 2008.

METHODS

We obtained national mortality data for cystic fibrosis from the Office for National Statistics. From 1959 to 2000, the Registrar General's Social Class coded socioeconomic status as manual or non-manual. From 2001 onwards, the National Statistics Socioeconomic Classification was implemented and socioeconomic status was split into three groups: professional and managerial, intermediate, and routine and manual. We calculated median age at death for every study year. We calculated the effects of sex and socioeconomic status on the odds of death above the median age at death for every study decade using logistic regression.

RESULTS

From 1959 to 2008, 6750 deaths were attributed to cystic fibrosis in England and Wales. Males were more likely to die above the annual median age at death than females (from 1959 to 1999, adjusted odds ratio for socioeconomic status 1.28, 95% confidence intervals 1.13 to 1.45; from 2000 to 2008, 1.57, 1.18 to 2.08). Individuals in the highest socioeconomic class were also more likely to die above the median age of death than those in the lowest socioeconomic class (from 1959 to 2000, adjusted odds ratio for sex 2.50, 2.16 to 2.90; from 2001 to 2008, 1.89, 1.20 to 2.97).

CONCLUSIONS

Socioeconomic status and sex remain strong determinants of survival from cystic fibrosis in England and Wales, and the magnitude of these effects does not appear to have substantially reduced over time.

A review of interventions for reduction of residential environmental tobacco smoke exposures among children

OBJECTIVE

To describe individual-level interventions to reduce residential environmental tobacco smoke (ETS) exposure among children and to summarize the evidence of the effectiveness of the interventions.

PATIENTS AND METHODS

A search of electronic databases (from 1987 to 1998) was conducted for studies designed to reduce ETS exposure of children through the use of interventions that included strategies other than parental smoking cessation. Twelve articles that presented nine unique interventions (six interventions were designed for well children and three interventions targeted children with asthma) were found. Information about location, target population, design, sample size, tested intervention and results were summarized for each study.

RESULTS

Only one of the six interventions designed for well children produced significant reductions in ETS exposure, while all three of the interventions that targeted children with asthma reported small to moderate reductions in ETS exposure or respiratory symptoms.

CONCLUSIONS

The number of interventions for ETS reduction published to date is miniscule relative to the magnitude of the associated health problems. Some ETS reduction interventions for children have shown significant reductions in exposure, but most interventions, especially those designed for well children, have had little effect. Little is known about which specific intervention components may be effective. Parental characteristics that may predict positive response to intervention efforts have not been identified. More research is needed to develop effective interventions that can be integrated with physician visits in the perinatal and early childhood periods. Adapting standard guidelines on counselling for parental smoking cessation may be a promising approach if the barriers identified by health professionals can be addressed adequately.

Modifier genes in Mendelian disorders: the example of cystic fibrosis

In the past three decades, scientists have had immense success in identifying genes and their variants that contribute to an array of diseases. While the identification of such genetic variants has informed our knowledge of the etiologic bases of diseases, there continues to be a substantial gap in our understanding of the factors that modify disease severity. Monogenic diseases provide an opportunity to identify modifiers as they have uniform etiology, detailed phenotyping of affected individuals, and familial clustering. Cystic fibrosis (CF) is among the more common life-shortening recessive disorders that displays wide variability in clinical features and survival. Considerable progress has been made in elucidating the contribution of genetic and nongenetic factors to CF. Allelic variation in CFTR, the gene responsible for CF, correlates with some aspects of the disease. However, lung function, neonatal intestinal obstruction, diabetes, and anthropometry display strong genetic control independent of CFTR, and candidate gene studies have revealed genetic modifiers underlying these traits. The application of genome-wide techniques holds great promise for the identification of novel genetic variants responsible for the heritable features and complications of CF. Since the genetic modifiers are known to alter the course of disease, their protein products become immediate targets for therapeutic intervention.

Quantification of the relative contribution of environmental and genetic factors to variation in cystic fibrosis lung function

OBJECTIVE

To assess the relative contributions of environmental and genetic factors to variation in cystic fibrosis (CF) lung disease.

STUDY DESIGN

Genetic and environmental contributions were quantified by use of intrapair correlations and differences in CF-specific forced expiratory volume in 1 second measures from 134 monozygous twins and 272 dizygous twins and siblings while in different living environments (ie, living with parents vs living alone), as well as by use of intraindividual differences in pulmonary function from a separate group of 80 siblings.

RESULTS

Pulmonary function among monozygous twins was more similar than among dizygous twin and sibling pairs, regardless of living environment, affirming the role of genetic modifiers in CF pulmonary function. Regression modeling revealed that genetic factors account for 50% of pulmonary function variation, unique environmental or stochastic factors (36%), and shared environmental factors (14%; P < .0001). The intraindividual analysis produced similar estimates for the contributions of the unique and shared environment. The shared environment effects appeared primarily because of living with a sibling with CF (P = .003), rather than factors within the parental household (P = .310).

CONCLUSIONS

Genetic and environmental factors contribute equally to pulmonary function variation in CF. Environmental effects are dominated by unique and stochastic effects rather than common exposures.

Baseline characteristics and factors associated with nutritional and pulmonary status at enrollment in the cystic fibrosis EPIC observational cohort

SUMMARY BACKGROUND

The EPIC Observational Study is an ongoing prospective cohort study investigating risk factors for and clinical outcomes associated with early Pseudomonas aeruginosa (Pa) acquisition in young children with cystic fibrosis (CF).

OBJECTIVES AND HYPOTHESIS

To describe the baseline characteristics of the cohort and evaluate associations between potential risk factors and nutritional and respiratory characteristics at enrollment. We hypothesized that distinct demographic and environmental risk factors could be identified for poorer nutritional status and lung function at enrollment.

METHODS

During 2004-2006, 1,700 children with CF were enrolled at 59 US CF centers. Children <or=12 years were eligible if they had no prior Pa infection (Pa-Never) or, if prior isolation of Pa from respiratory cultures, at least a 2-year history of Pa negative cultures (Pa-Past).

RESULTS

One thousand one hundred seventeen participants (65.7%) were Pa-Never and 583 (34.3%) Pa-Past. Pa-never patients had a lower proportion of CFTR genotypes with both mutations in functional classes I, II, or III), higher lung function and less respiratory symptoms. Diagnosis after newborn or prenatal screening was associated with significantly higher mean weight, height, and FEV(1) at enrollment, while maternal smoking during pregnancy appeared to worsen these parameters.

CONCLUSIONS

Children in this cohort with a remote history of Pa infection had a higher proportion of CFTR genotypes associated with severely reduced CFTR function as well as lower lung function and more respiratory symptoms than those without prior Pa infection. These observed differences in respiratory indices may reflect the impact of prior Pa airway infection and/or of CFTR genotype or other genetic factors predisposing both to earlier Pa acquisition and more severe lung disease. Key characteristics associated with nutritional and pulmonary status at enrollment included diagnosis after prenatal or neonatal screening (protective) and in utero cigarette exposure (harmful).

Genetic and non-genetic determinants of outcomes in cystic fibrosis

The treatment of cystic fibrosis has improved significantly over the past three decades. Median survival has improved by decades and is now estimated to be 37 years. Many factors contribute to improvements in disease severity and outcome. This paper reviews the current evidence of three groups of important factors: genetic, environmental and healthcare related.

Interactions between secondhand smoke and genes that affect cystic fibrosis lung disease

CONTEXT

Disease variation can be substantial even in conditions with a single gene etiology such as cystic fibrosis (CF). Simultaneously studying the effects of genes and environment may provide insight into the causes of variation.

OBJECTIVE

To determine whether secondhand smoke exposure is associated with lung function and other outcomes in individuals with CF, whether socioeconomic status affects the relationship between secondhand smoke exposure and lung disease severity, and whether specific gene-environment interactions influence the effect of secondhand smoke exposure on lung function.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective assessment of lung function, stratified by environmental and genetic factors. Data were collected by the US Cystic Fibrosis Twin and Sibling Study with missing data supplemented by the Cystic Fibrosis Foundation Data Registry. All participants were diagnosed with CF, were recruited between October 2000 and October 2006, and were primarily from the United States.

MAIN OUTCOME MEASURES

Disease-specific cross-sectional and longitudinal measures of lung function.

RESULTS

Of 812 participants with data on secondhand smoke in the home, 188 (23.2%) were exposed. Of 780 participants with data on active maternal smoking during gestation, 129 (16.5%) were exposed. Secondhand smoke exposure in the home was associated with significantly lower cross-sectional (9.8 percentile point decrease; P < .001) and longitudinal lung function (6.1 percentile point decrease; P = .007) compared with those not exposed. Regression analysis demonstrated that socioeconomic status did not confound the adverse effect of secondhand smoke exposure on lung function. Interaction between gene variants and secondhand smoke exposure resulted in significant percentile point decreases in lung function, namely in CFTR non-DeltaF508 homozygotes (12.8 percentile point decrease; P = .001), TGFbeta1-509 TT homozygotes (22.7 percentile point decrease; P = .006), and TGFbeta1 codon 10 CC homozygotes (20.3 percentile point decrease; P = .005).

CONCLUSIONS

Any exposure to secondhand smoke adversely affects both cross-sectional and longitudinal measures of lung function in individuals with CF. Variations in the gene that causes CF (CFTR) and a CF-modifier gene (TGFbeta1) amplify the negative effects of secondhand smoke exposure.

[The effects of tobacco on children]

INTRODUCTION

Smoking remains an important topic. It is estimated that at present half the children born in France have been, or will be, exposed to the toxic effects of passive smoking. This paper aims to review the evidence of the effects of passive smoking, both intra and extra-uterine.

STATE OF THE ART

Extra-uterine passive smoking is implicated in numerous respiratory (asthma, allergy, infections...) and non respiratory diseases (neoplastic, dental, ophthalmic, digestive, cardio-vascular and infective). Intra-uterine exposure is even more dangerous and leads to abnormalities of the pregnancy (placental abnormalities, prematurity...), of the foetus (behavioural problems, malformations) and long term problems for the unborn child. Passive smoking is responsible for pulmonary morphological abnormalities (pulmonary hypoplasia, reduction in elasticity, increased deposition of collagen and alteration of alveolar structure) and functional disorders (reduced compliance, increased airways resistance, bronchial hyperreactivity). Finally it causes a disturbance of respiratory control, promoting all the factors responsible for sudden cot death.

CONCLUSIONS

The ill effects of passive smoking fully justify efforts to inform and persuade the medical profession of its duty to fight this scourge.

Benefits of breastfeeding in cystic fibrosis: a single-centre follow-up survey

AIM

To study the effect of breastfeeding (BF) on growth, lung function and number of infections during the first 3 years of life in children with cystic fibrosis (CF).

MATERIAL AND METHODS

One hundred forty-six CF patients, 5-18 years old, were recruited at their annual care visit. Information about infant feeding, psychosocial and socioeconomic conditions and smoking exposure was obtained by interviews. Anthropometric parameters at 1 year of age and the number of infections and hospitalisations during the first 3 years of life were obtained from clinical charts. Anthropometrics and pulmonary function parameters were obtained at enrollment.

RESULTS

In CF patients, particularly those with pancreatic insufficiency, the prevalence of BF was lower than the general Italian population. After multivariate analysis patients with prolonged BF showed higher values of CED expiratory volume in 1 sec (FEV-1) (p = 0.001) and a lower number of infections during the first 3 years of life (p = 0.098).

CONCLUSION

Prolonged BF is beneficial in children with CF and may protect them against decline of pulmonary function. Particular attention should be paid to promote BF in infants with CF.

Heritability of lung disease severity in cystic fibrosis

RATIONALE

Obstructive lung disease, the major cause of mortality in cystic fibrosis (CF), is poorly correlated with mutations in the disease-causing gene, indicating that other factors determine severity of lung disease.

OBJECTIVES

To quantify the contribution of modifier genes to variation in CF lung disease severity.

METHODS

Pulmonary function data from patients with CF living with their affected twin or sibling were converted into reference values based on both healthy and CF populations. The best measure of FEV(1) within the last year was used for cross-sectional analysis. FEV(1) measures collected over at least 4 years were used for longitudinal analysis. Genetic contribution to disease variation (i.e., heritability) was estimated in two ways: by comparing similarity of lung function in monozygous (MZ) twins (approximately 100% gene sharing) with that of dizygous (DZ) twins/siblings (approximately 50% gene sharing), and by comparing similarity of lung function measures for related siblings to similarity for all study subjects.

MEASUREMENTS AND MAIN RESULTS

Forty-seven MZ twin pairs, 10 DZ twin pairs, and 231 sibling pairs (of a total of 526 patients) with CF were studied. Correlations for all measures of lung function for MZ twins (0.82-0.91, p < 0.0001) were higher than for DZ twins and siblings (0.50-0.64, p < 0.001). Heritability estimates from both methods were consistent for each measure of lung function and ranged from 0.54 to 1.0. Heritability estimates generally increased after adjustment for differences in nutritional status (measured as body mass index z-score).

CONCLUSIONS

Our heritability estimates indicate substantial genetic control of variation in CF lung disease severity, independent of CFTR genotype.

Epidemiology - identifying the causes and preventability of cancer?

It has been almost 25 years since Doll and Peto performed their landmark analysis of epidemiological data to identify the causes of cancers and possible modes of cancer prevention. Since then, there have been many additional studies of cancer incidence using various epidemiological techniques. These studies revealed expanded opportunities for cancer prevention through approaches that include vaccination, increased physical activity, weight control and avoidance of post-menopausal hormone therapy.

Modifier genetics: cystic fibrosis

Cystic fibrosis (CF) is the most common lethal autosomal recessive disorder in the Caucasian population, affecting about 30,000 individuals in the United States. The gene responsible for CF, the CF transmembrane conductance regulator (CFTR), was identified 15 years ago. Substantial variation in the many aspects of the CF phenotype among individuals with the same CFTR genotype demonstrates that factors independent of CFTR exert considerable influence on outcome in CF. To date, the majority of published studies investigating the cause of disease variability in CF report associations between candidate genes and some aspect of the CF phenotype. However, a definitive modifier gene for CF remains to be identified. Despite the challenges posed by searches for modifier effects, studies of affected twins and siblings indicate that genetic factors play a substantial role in intestinal manifestations. Identifying the factors contributing to variation in pulmonary disease, the primary cause of mortality, remains a challenge for CF research.

Cystic fibrosis since 1938

Cystic fibrosis (CF) was distinguished from celiac disease in 1938. Then, it was a pathologic diagnosis, life expectancy was approximately 6 months, and the autosomal recessive disease was believed to arise from abnormal mucus plugging exocrine ducts. Death often occurred from lung infection. Discovery of the sweat electrolyte defect in 1953 and standardization of the sweat test in 1959 allowed identification of milder cases, and CF was no longer considered only a disorder of mucus. In 1955, establishment of centers with programs of aggressive, comprehensive care initiated striking improvement in longevity. The pillars of care established then (attention to nutrition, airway clearance, treatment of lung infection) remain today. In 1983, chloride transport was identified as the basic physiologic CF defect, accompanied by increased sodium reabsorption. In 1980, we learned that inflammation contributes independently to lung disease and constitutes an independent therapeutic target. In 1989, the discovery of the CF gene demonstrated the basic defect to be in a cAMP-regulated chloride channel. This afforded new diagnostic tests, opportunities for research, and prospects for using the gene as therapy. Since then, substantial advances in basic and clinical research catalyzed therapeutic improvements: median survival age now exceeds 30 years. The Cystic Fibrosis Foundation center network provides not only opportunity to conduct clinical trials but also means to disseminate new therapies. In the future, treatments directed at the basic defect can be expected, with concomitant improvements in morbidity and mortality.

Cystic fibrosis lung disease: genetic influences, microbial interactions, and radiological assessment

Cystic fibrosis (CF) is a multiorgan disease caused by mutation of the CF transmembrane conductance regulator (CFTR) gene. Obstructive lung disease is the predominant cause of morbidity and mortality; thus, most efforts to improve outcomes are directed toward slowing or halting lung-disease progression. Current therapies, such as mucolytics, airway clearance techniques, bronchodilators, and antibiotics, aim to suppress airway inflammation and the processes that stimulate it, namely, retention and infection of mucus plaques at the airway surface. New approaches to therapy that aim to ameliorate specific CFTR mutations or mutational classes by restoring normal expression or function are being investigated. Because of its sensitivity in detecting changes associated with early airway obstruction and regional lung disease, high-resolution CT (HRCT) complements pulmonary function testing in defining disease natural history and measuring response to both conventional and experimental therapies. In this review, perspectives on the genetics and microbiology of CF provide a context for understanding the increasing importance of HRCT and other imaging techniques in assessing CF therapies.

[Passive smoking]

INTRODUCTION

Environmental tobacco smoke is a recognized factor of morbidity and mortality. The first victims are children, sometimes starting from conception, but adults are not spared. In practice, evaluation of exposure to tobacco smoke can be achieved with more or less specific markers of tobacco smoke.

CURRENT KNOWLEDGE

Exposure of the fetus to maternal smoking and of the infant to environmental smoke can have a serious sometimes life-threatening impact. Such exposure increases the risk of spontaneous abortion, ectopic pregnancy, intrauterine growth retardation, premature membrane rupture, preterm birth, retroplacental hematoma, placenta praevia, and sudden infant death. Adult respiratory and cardiovascular disease are also influenced by environmental smoke. In France passive smoking causes premature death of 3000 persons per year.

PERSPECTIVES

Better knowledge of the risks of exposure to passive smoking can facilitate application of legislation with the objective of protecting non-smokers.

CONCLUSIONS

Rigorous application of current legislation is important to achieve the stated goals of prevention of smoking as well as assistance to cease smoking.

Relation of sweat chloride concentration to severity of lung disease in cystic fibrosis

In cystic fibrosis (CF), sweat chloride concentration has been proposed as an index of CFTR function for testing systemic drugs designed to activate mutant CFTR. This suggestion arises from the assumption that greater residual CFTR function should lead to a lower sweat chloride concentration, as well as protection against severe lung disease. This logic gives rise to the hypothesis that the lower the sweat chloride concentration, the less severe the lung disease. In order to test this hypothesis, we studied 230 patients homozygous for the DeltaF508 allele, and 34 patients with at least one allele associated with pancreatic sufficiency, born since January 1, 1955, who have pulmonary function data and sweat chloride concentrations recorded in our CF center database, and no culture positive for B. cepacia. We calculated a severity index for pulmonary disease, using an approach which takes into account all available pulmonary function data as well as the patient's current age and survival status. Patients with alleles associated with pancreatic sufficiency had significantly better survival (P = 0.0083), lower sweat chloride concentration (81.4 +/- 23.8 vs. 103.2 +/- 14.2 mEq/l, P < 0.0001), slower rate of decline of FEV(1) % predicted (-0.75 +/- 0.34 vs. -2.34 +/- 0.17% predicted per year), and a better severity index than patients homozygous for the DeltaF508 allele (median 73rd percentile vs. median 55th percentile, P = 0.0004). However, the sweat chloride concentration did not correlate with the severity index, either in the population as a whole, or in the population of patients with alleles associated with pancreatic sufficiency, who are thought to have some residual CFTR function. These data suggest that, by itself, sweat chloride concentration does not necessarily predict a milder pulmonary course in patients with cystic fibrosis.

Survey of breast-feeding practices and outcomes in the cystic fibrosis population

The aim of this study was to survey cystic fibrosis (CF) patients to determine the frequency of breast-feeding and its association with onset and severity of CF symptoms. Three thousand, two hundred questionnaires were sent to 30 accredited CF centers for anonymous completion. Eight hundred and sixty-three questionnaires were returned and scanned into a database. All results were adjusted for age at time of filling out the questionnaire. Age at onset of symptoms, percent forced expired volume in 1 sec (FEV1%) predicted, and intravenous (IV) antibiotic use were analyzed based on breast-feeding history. Approximately 49% of respondents received human breast milk at some time, but only 18% were exclusively breast-fed. Breast-feeding exclusively for greater than 6 months was associated with a decrease in disease severity based on recent intravenous antibiotic use compared to no breast-feeding (P = 0.03). There was no statistically significant change in onset of symptoms in the setting of breast-feeding; however, a trend toward delayed onset was seen in those receiving human milk. Fifty-three percent of those who breast-fed exclusively > or = 6 months had FEV1% values > 90%, compared to 47% of those not breast-fed. This is a suggestive but not statistically significant difference. In conclusion, breast-feeding for > or = 6 months is associated with decreased use of intravenous antibiotics in the 2 years prior to administering the questionnaire. This survey indicates that breast-feeding is not harmful to children with CF, and may be beneficial.