Association of poor clinical status and heavy exposure to tobacco smoke in patients with cystic fibrosis who are homozygous for the F508 deletion

Lung function and secondhand smoke exposure among children with cystic fibrosis: A Bayesian meta-analysis

BACKGROUND

Secondhand smoke exposure, an important environmental health factor in cystic fibrosis (CF), remains uniquely challenging to children with CF as they strive to maintain pulmonary function during early stages of growth and throughout adolescence. Despite various epidemiologic studies among CF populations, little has been done to coalesce estimates of the association between secondhand smoke exposure and lung function decline.

METHODS

A systematic review was performed using PRISMA guidelines. A Bayesian random-effects model was employed to estimate the association between secondhand smoke exposure and change in lung function (measured as FEV1% predicted).

RESULTS

Quantitative synthesis of study estimates indicated that second-hand smoke exposure corresponded to a significant drop in FEV1 (estimated decrease: -5.11% predicted; 95% CI: -7.20, -3.47). The estimate of between-study heterogeneity was 1.32% predicted (95% CI: 0.05, 4.26). There was moderate heterogeneity between the 6 analyzed studies that met review criteria (degree of heterogeneity: I2=61.9% [95% CI: 7.3-84.4%] and p = 0.022 from the frequentist method.) CONCLUSIONS: Our results quantify the impact at the pediatric population level and corroborate the assertion that secondhand smoke exposure negatively affects pulmonary function in children with CF. Findings highlight challenges and opportunities for future environmental health interventions in pediatric CF care.

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.

Cessation of smoke exposure improves pediatric CF outcomes: Longitudinal analysis of CF Foundation Patient Registry data

BACKGROUND

Tobacco smoke exposure is a major risk factor for the health of children and adolescents with CF. In this study, we assess whether cessation of smoke exposure is associated with improved outcomes in this population.

METHODS

We used annualized and encounter-based data from the U.S. CF Foundation Patient Registry (2006-2018) on all individuals born 1998-2010. The analytical sample included those who ever reported second-hand smoke exposure (daily or weekly), ever lived with a smoker, or ever reported smoking themselves. We used non-linear mixed models for pulmonary exacerbations and linear mixed models for ppFEV₁ and BMI as a function of ceased exposure.

RESULTS

The sample included 3,633 individuals contributing 19,629 person-years. Cessation of smoke exposure reduced the odds of a pulmonary exacerbation in 12 months by 17% (OR 0.83, p < 0.001) in the first year of cessation, with an additional 6% decrease (OR 0.94, p = 0.003) for each additional year of cessation. Cessation was associated with improvements in ppFEV₁ and BMI: 0.7% ppFEV₁ increase (p < 0.001) in the first year of cessation and 0.4% increase (p = 0.001) for each additional year of cessation; 1% increase in BMI percentile (p < 0.001) in the first year of cessation plus 0.4% increase (p = 0.009) for each additional year. Three years of cessation reduce the predicted probability of a pulmonary exacerbation in 12 months by 8% and improve ppFEV₁ and BMI by 2%.

CONCLUSION

Eliminating smoke exposure may reduce pulmonary exacerbations and improve respiratory and nutritional outcomes in children and adolescents with CF. Both smoking cessation and exposure prevention should be prioritized in pediatric CF care.

Tensin 1 (TNS1) is a modifier gene for low body mass index (BMI) in homozygous [F508del]CFTR patients

Cystic fibrosis (CF) is a life‐limiting autosomal recessive genetic disease caused by variants in the CFTR gene, most commonly by the [F508del] variant. Although CF is a classical Mendelian disease, genetic variants in several modifier genes have been associated with variation of the clinical phenotype for pulmonary and gastrointestinal function and urogenital development. We hypothesized that whole genome sequencing of a well‐phenotyped CF populations might identify novel variants in known, or hitherto unknown, modifier genes. Whole genome sequencing was performed on the Illumina HiSeq X platform for 98 clinically diagnosed cystic fibrosis patient samples from the Adult CF Clinic at the University of California San Diego (UCSD). We compared protein‐coding, non‐silent variants genome wide between CFTR [F508del] homozygotes vs CFTR compound heterozygotes. Based on a single variant score test, we found 3 SNPs in common variants (MAF >5%) that occurred at significantly different rates between homozygous [F508del]CFTR and compound heterozygous [F508del]CFTR patients. The 3 SNPs were all located in one gene on chromosome 2: Tensin 1 (TNS1: rs3796028; rs2571445: and rs918949). We observed significantly lower BMIs in homozygous [F508del]CFTR patients who were also homozygous for Tensin 1 rs918949 (T/T) (p = 0.023) or rs2571445 (G/G) (p = 0.02) variants. The Tensin 1 gene is thus a potential modifier gene for low BMI in CF patients homozygous for the [F508del]CFTR variant.

Tobacco smoke exposure in pediatric cystic fibrosis: A qualitative study of clinician and caregiver perspectives on smoking cessation

OBJECTIVE

Tobacco smoke exposure has negative impacts on the lung health of children with cystic fibrosis (CF), yet evidence-based strategies for smoking cessation have not been tested with or tailored to CF caregivers. This qualitative study identified barriers and facilitators of smoking cessation in this population and outlined potential interventional approaches.

METHODS

We conducted semi-structured interviews with CF familial caregivers who were current or former smokers, and with members of the CF care team. We asked about experiences, practices, and prerequisites for a successful program. Interviews were recorded, transcribed verbatim, and coded by two investigators. Analysis used a thematic approach guided by the PRECEDE model, which identifies predisposing (intrapersonal), reinforcing (interpersonal), and enabling (structural) factors relevant to health behaviors and programs.

RESULTS

Seventeen interviews were conducted-eight with familial caregivers and nine with CF team members. Whereas caregivers provided greater insight into internal difficulties and motivators to quit smoking, clinicians offered more extensive input on barriers and solutions related to the clinical environment. Based on study recommendations, a successful tobacco cessation program should include (a) family education about the harms of smoke exposure for children with CF; (b) screening for exposure, ideally with biochemical verification; (c) access to trained tobacco counselors; (d) affordable pharmacotherapy; and (e) outpatient follow-up of those undergoing tobacco treatment.

CONCLUSION

This qualitative study revealed intrapersonal, interpersonal, and structural barriers to eliminating tobacco smoke exposure in children with CF, outlined opportunities to address these barriers, and made recommendations for a comprehensive tobacco cessation strategy.

Tobacco smoke exposure and socioeconomic factors are independent predictors of pulmonary decline in pediatric cystic fibrosis

BACKGROUND

Pulmonary decline in CF is heterogeneous, with socio-environmental factors contributing to this variability. Few studies have attempted to disentangle the effects of tobacco smoke exposure and socioeconomic factors on lung function deterioration in pediatric CF. The current study evaluates their contributions longitudinally across the entire U.S. CF care network population.

METHODS

Data from the CF Foundation Patient Registry were obtained on all individuals who at the end of 2016 were 6-18 years old. Lung function measures (ppFEV₁) for each person were calculated at each attained age. Multivariable analyses used mixed modeling to assess the impact of smoke exposure and socioeconomic factors on initial lung function and change over time.

RESULTS

The sample included 10,895 individuals contributing 65,581 person years. At age 6, ppFEV₁ of smoke-exposed children was 4.7% lower than among unexposed. The deficit persisted through age 18. In adjusted mixed models, smoke exposure and socioeconomic factors had independent, additive associations with lung function. Median ppFEV₁ declined 2.4% with smoke exposure, 4.9% with lower paternal education, 0.3% with public insurance, and increased 0.2% with each $10,000 annual household income. The effect of smoke exposure on ppFEV₁ was larger in disadvantaged children compared to privileged counterparts (3.2% vs 1.2%).

CONCLUSIONS

Smoke exposure and socioeconomic factors are independent risk factors for decreased ppFEV₁ in pediatric CF. Smoking cessation strategies should be emphasized at the time of CF diagnosis and reiterated during infancy and early childhood. Interventions may be prioritized in disadvantaged families, where the exposure has a disproportionately large effect.

The demographics of adverse outcomes in cystic fibrosis

Understanding variability in cystic fibrosis (CF) health outcomes requires an understanding of factors that go far beyond Cystic Fibrosis Transmembrane Receptor (CFTR) function caused by different gene mutations. Social and environmental factors that influence health have a significant influence on the trajectory of health in CF and in other chronic diseases. In this article, we review demographic factors associated with poorer health outcomes in CF, known and postulated biological mechanisms of these outcomes, and interventions that healthcare teams can implement that may reduce outcome disparities.

Smoking and microbiome in oral, airway, gut and some systemic diseases

The human microbiome harbors a diverse array of microbes which establishes a mutually beneficial relation with the host in healthy conditions, however, the dynamic homeostasis is influenced by both host and environmental factors. Smoking contributes to modifications of the oral, lung and gut microbiome, leading to various diseases, such as periodontitis, asthma, chronic obstructive pulmonary disease, Crohn’s disease, ulcerative colitis and cancers. However, the exact causal relationship between smoking and microbiome alteration remains to be further explored.

Induced pluripotent stem cells for treating cystic fibrosis: State of the science

Induced pluripotent stem cells (iPSCs) are a recently developed technology in which fully differentiated cells such as fibroblasts from individual CF patients can be repaired with [wildtype] CFTR, and reprogrammed to differentiate into fully differentiated cells characteristic of the proximal and distal airways. Here, we review properties of different epithelial cells in the airway, and the in vitro genetic roadmap which iPSCs follow as they are step-wise differentiated into either basal stem cells, for the proximal airway, or into Type II Alveolar cells for the distal airways. The central theme is that iPSC-derived basal stem cells, are penultimately dependent on NOTCH signaling for differentiation into club cells, goblet cells, ciliated cells, and neuroendocrine cells. Furthermore, given the proper matrix, these cellular progenies are also able to self-assemble into a fully functional pseudostratified squamous proximal airway epithelium. By contrast, club cells are reserve stem cells which are able to either differentiate into goblet or ciliated cells, but also to de-differentiate into basal stem cells. Variant club cells, located at the transition between airway and alveoli, may also be responsible for differentiation into Type II Alveolar cells, which then differentiate into Type I Alveolar cells for gas exchange in the distal airway. Using gene editing, the mutant CFTR gene in iPSCs from CF patients can be repaired, and fully functional epithelial cells can thus be generated through directed differentiation. However, there is a limitation in that the lung has other CFTR-dependent cells besides epithelial cells. Another limitation is that there are CFTR-dependent cells in other organs which would continue to contribute to CF disease. Furthermore, there are also bystander or modifier genes which affect disease outcome, not only in the lung, but specifically in other CF-affected organs. Finally, we discuss future personalized applications of the iPSC technology, many of which have already survived the "proof-of-principle" test. These include (i) patient-derived iPSCs used as a "lung-on-a-chip" tool for personalized drug discovery; (ii) replacement of mutant lung cells by wildtype lung cells in the living lung; and (iii) development of bio-artificial lungs. It is hoped that this review will give the reader a roadmap through the most complicated of the obstacles, and foster a guardedly optimistic view of how some of the remaining obstacles might one day be overcome.

Cigarette smoke activates CFTR through ROS-stimulated cAMP signaling in human bronchial epithelial cells

Air pollution stimulates airway epithelial secretion through a cholinergic reflex that is unaffected in cystic fibrosis (CF), yet a strong correlation is observed between passive smoke exposure in the home and impaired lung function in CF children. Our aim was to study the effects of low smoke concentrations on cystic fibrosis transmembrane conductance regulator (CFTR) function in vitro. Cigarette smoke extract stimulated robust anion secretion that was transient, mediated by CFTR, and dependent on cAMP-dependent protein kinase activation. Secretion was initiated by reactive oxygen species (ROS) and mediated by at least two distinct pathways: autocrine activation of EP4 prostanoid receptors and stimulation of Ca2+ store-operated cAMP signaling. The response was absent in cells expressing the most common disease-causing mutant F508del-CFTR. In addition to the initial secretion, prolonged exposure of non-CF bronchial epithelial cells to low levels of smoke also caused a gradual decline in CFTR functional expression. F508del-CFTR channels that had been rescued by the CF drug combination VX-809 (lumacaftor) + VX-770 (ivacaftor) were more sensitive to this downregulation than wild-type CFTR. The results suggest that CFTR-mediated secretion during acute cigarette smoke exposure initially protects the airway epithelium while prolonged exposure reduces CFTR functional expression and reduces the efficacy of CF drugs.

Pulmonary function disparities exist and persist in Hispanic patients with cystic fibrosis: A longitudinal analysis

BACKGROUND

Hispanic patients with cystic fibrosis (CF) have decreased life expectancy compared to non-Hispanic white patients. Pulmonary function is a main predictor of life expectancy in CF. Ethnic differences in pulmonary function in CF have been understudied. The objective was to compare longitudinal pulmonary function between Hispanic and non-Hispanic white patients with CF.

METHODS

This cohort study of 15 018 6-25 years old patients in the CF Foundation Patient Registry from 2008 to 2013 compared FEV₁ percent predicted and longitudinal change in FEV₁ percent predicted in Hispanic to non-Hispanic white patients. We used linear mixed effects models with patient-specific slopes and intercepts, adjusting for 14 demographic and clinical variables. We did sub-analyses by CFTR class, F508del copies, and PERT use.

RESULTS

Hispanic patients had lower FEV₁ percent predicted (79.9%) compared with non-Hispanic white patients (85.6%); (-5.8%, 95%CI -6.7% to -4.8%, P < 0.001), however, there was no difference in FEV₁ decline over time. Patients on PERT had a larger difference between Hispanic and non-Hispanic white patients in FEV₁ percent predicted than patients not on PERT (-6.0% vs -4.1%, P = 0.02). The ethnic difference in FEV₁ percent predicted was not statistically significant between CFTR classes (Class I-III: -6.1%, Class IV-V: -5.9%, Unclassified: -5.7%, P > 0.05) or between F508del copies (None: -7.6%, Heterozygotes: -5.6%, Homozygotes: -5.3%, P > 0.05).

CONCLUSIONS

Disparities in pulmonary function exist in Hispanic patients with CF early in life and then persist without improving or worsening over time. It is valuable to investigate the factors contributing to pulmonary function in Hispanic patients with CF.

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.

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.

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.

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).

Cystic Fibrosis Foundation evidence-based guidelines for management of infants with cystic fibrosis

Newborn screening for cystic fibrosis (CF) offers the opportunity for early medical and nutritional intervention that can lead to improved outcomes. Management of the asymptomatic infant diagnosed with CF through newborn screening, prenatal diagnosis, or sibling screening is different from treatment of the symptomatically diagnosed individual. The focus of management is on maintaining health by preventing nutritional and respiratory complications. The CF Foundation convened a committee to develop recommendations based on a systematic review of the evidence and expert opinion. These guidelines encompass monitoring and treatment recommendations for infants diagnosed with CF and are intended to help guide families, primary care providers, and specialty care centers in the care of infants with CF.

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.

Effect of secondhand cigarette smoke, RSV bronchiolitis and parental asthma on urinary cysteinyl LTE4

Cysteinyl leukotrienes promote airway inflammation, bronchoconstriction and mucus hypersecretion. Cigarette smoking and respiratory syncytial virus (RSV) bronchiolitis are known to increase urinary cysteinyl leukotriene E4 (uLTE4), the end product of the cysteinyl leukotriene biosynthetic pathway. We tested the following hypotheses: (1) Secondhand smoke (SHS) exposure increases uLTE4 in well infants and in those hospitalized for RSV bronchiolitis; (2) Length of hospital stay for those with RSV bronchiolitis correlates with uLTE4; and (3) Infants with parent(s) with asthma will have higher uLTE4. Parental asthma for infants hospitalized with RSV bronchiolitis (n = 79) and Well babies (n = 31) was determined by questionnaire. Urine was analyzed for LTE4, cotinine, and creatinine. SHS exposure was determined by cotinine to creatinine ratio. Chi square, or t-tests were used to determine significant differences between two groups. A three-way analysis of variance compared the effects of SHS exposure and parental asthma on uLTE4 in Well versus RSV babies. Independent variables predicting length of hospital stay were determined by stepwise multiple regression. High SHS exposure and RSV significantly increased uLTE4. The SHS induced increase in uLTE4 was seen in infants with no parental asthma but not in those with parental asthma. Length of hospital stay positively correlated with uLTE4. We concluded that SHS exposure may increase the severity of bronchiolitis in RSV-infected infants by enhancing production of cysLTs in infants with no parental asthma.

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.

Adolescents with a chronic condition: challenges living, challenges treating

In this review, we aim to focus attention on the interaction between adolescents with chronic conditions and the health systems that support them. At least 12% of adolescents live with a chronic condition. Some conditions are characterised by increasing incidence (eg, diabetes) or improving survival rates (eg, cystic fibrosis), while others are concerning because of differentially poorer outcomes in adolescents in comparison to both children and adults (eg cancer). Growing evidence suggests that young people with chronic conditions are doubly disadvantaged--engaging in risky behaviours to at least similar if not higher rates as healthy peers, while having the potential for greater adverse health outcomes from these behaviours. In addition to efforts at improving survival, in order to improve their life chances, we need to better understand how the social and emotional outcomes of young people with a chronic disease can be improved, and better support young people's emerging capacity for self-management.

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.

Effect of ambient air pollution on pulmonary exacerbations and lung function in cystic fibrosis

Information concerning the impact of environmental factors on cystic fibrosis (CF) is limited. We conducted a cohort study to assess the impact of air pollutants in CF. The study included patients over the age of 6 years enrolled in the Cystic Fibrosis Foundation National Patient Registry in 1999 and 2000. Exposure was assessed by linking air pollution values from the Aerometric Information Retrieval System with the patients' home zip code. After adjusting for confounders, a 10 microg/m(3) rise in particulate matter (both with a median aerodynamic diameter of 10 microm (PM(10)) or less and with an aerodynamic diameter of 2.5 microm or less (PM(2.5)) was associated with an 8% (95% confidence interval [CI], 2-15%) and 21% (95% CI, 7-33%) increase in the odds of two or more exacerbations, respectively; a 10-ppb rise in ozone was associated with a 10% (95% CI, 3-17%) increase in odds of two or more exacerbations. For every increase in PM(2.5) of 10 microg/m(3), there was an associated fall in FEV(1) of 24 ml (7-40) (95% CI) after adjusting for confounders. PM(2.5)'s association with mortality did not achieve statistical significance (adjusted RR = 1.32 per 10 microg/m(3) 0.91-1.93; 95% CI). Annual average exposures to particulate air pollution was associated with an increased risk of pulmonary exacerbations and a decline in lung function, suggesting a role of environmental exposures on prognosis in CF.

Median household income and mortality rate in cystic fibrosis

CONTEXT

Poverty has been shown to be a determinant of health outcomes in many epidemiologic studies.

OBJECTIVE

The goal of this study was to assess the association between household income and the mortality rate in cystic fibrosis (CF) patients.

DESIGN, SETTING, AND PATIENTS

We selected white patients diagnosed before 18 years old and having 1 or more records in the Cystic Fibrosis Foundation Patient Registry since 1991. These 23 817 patients were linked to the 1990 US Census by their zip code of residence. The median household income was adjusted for state level differences in cost of living using the 1998 Consumer Price Index.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

We examined the association between categories of the median household income and the mortality rate. We examined the association between income categories and age-related changes in pulmonary function and body weight as well as specific nutritional and pulmonary therapies.

RESULTS

We found a strong monotonic association between the median household income and the mortality rate. The test of trend was significant, and this effect was maintained after adjustment for a variety of patient and disease characteristics. When the lowest income category (<20 000 dollars) is compared with the highest (> or = 50 000 dollars), the adjusted incidence rates were 90.3 and 62.6 per 10 000 person years, respectively; this represents a 44% increased risk of death in the lowest income category. Patients living in areas with lower median household income also had consistently lower pulmonary function and body weight than did those living in higher income areas. The differences in weight percentiles and forced expiratory volume in 1 second are substantial in magnitude, they appear at an early age, and they persist into adulthood for these CF patients. Prescribed nutritional treatments and screening for CF-related diabetes were significantly higher among patients living in areas with lower median household income. Prescription of deoxyribonuclease and inhaled tobramycin was not significantly associated with median household income.

CONCLUSION

There was a strong association between lower household income and increased mortality rate among CF patients. Additional understanding of this effect will require more complete and direct measurement of socioeconomic status and a better understanding of treatment adherence, local environmental conditions, and especially the care of CF patients during the early years of life.

Association between genetically determined pancreatic status and lung disease in adult cystic fibrosis patients

STUDY OBJECTIVES

The association between genotype and phenotype in cystic fibrosis (CF) has been clearly established for pancreatic status, but not for lung disease.

DESIGN

Retrospective study.

SETTING

A respiratory unit of a teaching hospital.

PATIENTS

We studied 51 adult CF patients for whom current data and genotype were available. Thirty-seven patients carried two severe mutations associated with pancreatic insufficiency phenotype (group S). Fourteen patients carried at least one mild (and dominant) mutation associated with pancreatic sufficiency phenotype (group M).

MEASUREMENTS

We compared the course of the disease between the two groups, looking for a genotype/phenotype association for lung disease.

RESULTS

The mean age of the population was 30 years. Patients with two severe mutations presented more severe disease with earlier onset (1.7 years vs 7.9 years, p = 0.0001). They presented with a more severe respiratory impairment, with a lower mean FEV(1) (29% of predictive value vs 58% of predictive value, p < 0.001); a higher Pseudomonas colonization rate (97% vs 57%, p < 0.01); a more frequent end-stage respiratory insufficiency, defined by a FEV(1) < 30% (73% vs 29%, p < 0.05); and a more marked yearly decline of FEV(1) (3% vs 1.4%, p < 0.001). By multivariate logistic regression analysis, carrying two severe mutations was the only independent predictor of a terminal respiratory insufficiency (relative risk, 6.75; 95% confidence interval, 1.79 to 26.50; p = 0.003).

CONCLUSION

This study suggests that pulmonary disease appears to be associated with the severity of CF transmembrane regulator mutations.

[Evaluation of diagnosis and follow-up in screened children with cystic fibrosis in Normandy]

The neonatal screening programme in Normandy (France) allowed the formation of a homogenous cystic fibrosis (CF) cohort of 150 children diagnosed between 1980 and 1997. At the time of this retrospective study, 11 were deceased, out of which nine had meconium ileus (eight deaths after surgery, one at 5 years of age). Sixty children born between 1980 and 1993 in the Basse-Normandie region were followed up during a mean 80 months following similar protocols. The mean age at diagnosis was 41 days (SD = 27 d) for infants without meconium ileus. The occurrence of Pseudomonas aeruginosa (P. aeruginosa) infection and chronic colonization was studied using a monovariate followed by a multivariate analysis including the following variables: sex; meconium ileus; anthropometric data at birth and at diagnosis; pancreatic insufficiency; radiological data (Brasfield score); microbiology data at diagnosis; and genetic data. P. aeruginosa infection appeared earlier in children with pancreatic insufficiency (OR = 2.2; p < 0.05) or with radiological abnormalities (Brasfield score < 21) at diagnosis (OR = 3.9; p < 0.05). Meconium ileus (OR = 5.3; p < 0.01), pancreatic insufficiency (OR = 3.8; p < 0.01) and Brasfield score < 21 at diagnosis (OR = 5.6; p < 0.001) were prognosis factors for early chronic P. aeruginosa colonization. In CF children without meconium ileus, the major risk factor found through multivariate analysis for earlier infection and for earlier chronic colonization by P. aeruginosa was a diagnosis delay > 40 days (respectively OR = 4.6; p < 0.001 and OR = 10.4; p < 0.005). These results must be compared with the lower Brasfield score at diagnosis in infants diagnosed after 40 days of life (p < 0.01).

Trends in passive smoking in cystic fibrosis, 1993-1998

We set out to study trends in exposure to passive smoking in children with cystic fibrosis over a 5-year period. We also evaluated the effects of this exposure on lung function. Cross-sectional data were collected on 52 children in 1998 and compared with similar data collected on 56 children in 1993. Within these two groups, there were 34 children who were studied on both occasions. Data collected included: questionnaire information about family smoking habits; forced expiratory volume in 1 sec (FEV1); forced vital capacity (FVC); and measurements of urinary and salivary cotinine levels. Salivary cotinine was more closely related to family smoking behavior than urinary cotinine concentrations (r for salivary cotinine = 0.54, P < 0.001; r for urinary cotinine = 0.37, P = 0.008). In 1993, 26/56 (46%) households contained at least one smoker (smoking households) compared with 23/52 (44%) in 1998. In 1993, a median of 15 cigarettes was smoked/day in smoking households compared to 20 cigarettes/day in 1998. In the longitudinal group, there was a small, nonsignificant reduction in mean urinary cotinine levels (geometric mean, 1993 = 5.03 ng/mL; 1998 = 4.76 ng/mL; P = 0.4). There was no significant difference between the smoking and nonsmoking households in change in lung function over 5 years (fall in FEV1 in smoking households, 10.3% vs. 11.2% in nonsmoking households; P = 0.87). We conclude that in a group of children with cystic fibrosis followed over 5 years, there was little reduction in passive smoking exposure. We did not show a relationship between such exposure and decline in lung function. A larger study will be necessary to determine whether such an effect is present. .

Pulmonary outcome in cystic fibrosis is influenced primarily by mucoid Pseudomonas aeruginosa infection and immune status and only modestly by genotype

Whether allelic variants of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) independently contribute to pulmonary outcome in CF patients has not been resolved. We used both cross-sectional and mixed-model longitudinal analyses of data from CF patients that were at least 12 years old to determine the influence on pulmonary function (percent predicted forced expiratory volume [FEV(1)]) of the CFTR gene genotype, gender, mucoid Pseudomonas aeruginosa (MPA) infection status, presence of total opsonic antibody to MPA, and, separately, the opsonic antibody activity specific to the mucoid exopolysaccharide (MEP) surface antigen. Two different factors were independently associated with the lack of MPA infection: a high level of MEP-specific opsonic activity (MSOA), implicating an immunologically based mechanism of resistance to infection, and a lack of any type of opsonic antibody to MPA, indicative of no significant exposure or infection. This latter phenotype was found in a subset of CF patients who carried at least one uncommon CFTR gene allele suggestive of a genetic basis for resistance to infection in this group of older CF patients. For CF patients in whom both CFTR gene alleles were identified by screening for the 12 most common variants (75% of alleles), cross-sectional analysis showed that MPA infection was best correlated with lower percent predicted FEV(1), while genotype (two versus one DeltaF508 CFTR gene allele) and a low level of MSOA were associated with increased risk of infection. A mixed-model analysis of longitudinal spirometric measurements that considered multiple risk factors to derive regression equations was used to determine which clinical parameters had the greatest effect on the annual rate of decline in percent predicted FEV(1). This analysis showed that the CFTR gene genotype only modestly modified the constant (y intercept) of the derived equations, while gender and MPA infection status had the largest effects on annual rates of decline in percent predicted FEV(1). These results indicate that the CFTR genotype is usually not a primary determinant of pulmonary function in most CF patients, but gender and MPA infection status are. Infection status is potentially influenced by both immunologic (a high level of MSOA) and genetic factors, such as carriage of a CFTR gene allele that leads to a diagnosis of CF but still confers resistance to infection that is comparable to that of the wild-type CFTR gene.

Health effects of passive smoking-10: Summary of effects of parental smoking on the respiratory health of children and implications for research

BACKGROUND

Two recent reviews have assessed the effect of parental smoking on respiratory disease in children.

METHODS

The results of the systematic quantitative review published as a series in Thorax are summarised and brought up to date by considering papers appearing on Embase or Medline up to June 1998. The findings are compared with those of the review published recently by the Californian Environmental Protection Agency (EPA). Areas requiring further research are identified.

RESULTS

Overall there is a very consistent picture with odds ratios for respiratory illnesses and symptoms and middle ear disease of between 1.2 and 1.6 for either parent smoking, the odds usually being higher in pre-school than in school aged children. For sudden infant death syndrome the odds ratio for maternal smoking is about 2. Significant effects from paternal smoking suggest a role for postnatal exposure to environmental tobacco smoke. Recent publications do not lead us to alter the conclusions of our earlier reviews. While essentially narrative rather than systematic and quantitative, the findings of the Californian EPA review are broadly similar. In addition they have reviewed studies of the effects of environmental tobacco smoke on children with cystic fibrosis and conclude from the limited evidence that there is a strong case for a relationship between parental smoking and admissions to hospital. They also review data from adults of the effects of acute exposure to environmental tobacco smoke under laboratory conditions which suggest acute effects on spirometric parameters rather than on bronchial hyperresponsiveness. It seems likely that such effects are also present in children.

CONCLUSIONS

Substantial benefits to children would arise if parents stopped smoking after birth, even if the mother smoked during pregnancy. Policies need to be developed which reduce smoking amongst parents and protect infants and young children from exposure to environmental tobacco smoke. The weight of evidence is such that new prevalence studies are no longer justified. What are needed are studies which allow comparison of the effects of critical periods of exposure to cigarette smoke, particularly in utero, early infancy, and later childhood. Where longitudinal studies are carried out they should be analysed to look at the way in which changes in exposure are related to changes in outcome. Better still would be studies demonstrating reversibility of adverse effects, especially in asthmatic subjects or children with cystic fibrosis.

Outcome measures for clinical trials in cystic fibrosis. Summary of a Cystic Fibrosis Foundation consensus conference

The CFF Consensus Conference concluded with a summary of those outcome measures that would be most useful in studies of patients 6 years of age and older and those measures that would be most useful in studies of the younger population (< 6 years of age) (Table). These measures were further divided into biologic markers most appropriate for initial (phase I and phase II) clinical trials and those especially useful in large, multicenter (phase III) pivotal trials. There is an ongoing need to improve the accuracy and validity of currently available measures of biologic activity and clinical efficacy in CF, especially in the younger population. The conference participants recommended that the following eight issues be addressed as soon as possible: (1) definition of pulmonary exacerbation, (2) broadly applicable methods of testing pulmonary function in small children (ideally a single test for all ages), (3) a comprehensive severity-of-disease score for young children, (4) reliable methods of quantifying chest x-ray and CT scan changes in young patients, (5) simple, inexpensive measures of lung inflammation, (6) a centralized, uniform approach to the establishment of data monitoring committees, (7) a quality of well-being scale for small children, and (8) reliable, reproducible aerosol delivery systems with defined characteristics. In addition, participants recommended that better methods be developed for assessing patients' adherence to research protocols.

Passive smoking and lung function in cystic fibrosis

The relationship between passive exposure to cigarette smoking and objective measures of health was examined in 340 patients with cystic fibrosis attending a large hospital-based clinic. Patients who came from households with smokers did not differ from those living in smoke-free households in terms of nutritional status, clinical scores, spirometry, or colonization with Pseudomonas. The number of cigarettes smoked in the household was not significantly related to nutritional status, clinical score, spirometry, or hospitalization. Similar results were found when children 6 to 11 yr of age were analyzed separately, except that height percentile was negatively related to the number of cigarettes smoked in the household. The effects of household exposure to cigarette smoke were further evaluated by analyzing changes in nutritional status, clinical score, and spirometry over a 15-yr period among patients whose families never, always, stopped, or started smoking during this time. Height percentile increased slightly during this interval among those whose households never smoked, whereas no change occurred among patients whose households always smoked, and a decline was seen among patients whose households quit. These differences were statistically significant. Patients whose households never smoked had consistently higher pulmonary function measurements than did patients whose families always smoked, although the differences were not statistically significant. The rates of decline were similar in these two groups. Patients whose households stopped smoking had significantly lower pulmonary functions at the end of the study than did subjects whose households never smoked.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation between genotype and phenotype in patients with cystic fibrosis

BACKGROUND

Cystic fibrosis is the most common lethal autosomal recessive disorder among whites. Seventy-two percent of patients with this disease are homozygotes or compound heterozygotes for eight mutations of the cystic fibrosis transmembrane conductance regulator gene on chromosome 7: delta F508, G542X, R553X, W1282X, N1303K, 621 + 1G-->T, 1717-1G-->A, and R117H. We studied the relation between genotype and phenotype in patients from 14 countries.

METHODS

Each of 399 patients who were compound heterozygotes for delta F508 and one other mutation was matched with the delta F508 homozygote of the same sex who was the closest in age from the same center. A paired analysis was performed of the following outcome variables: age at diagnosis, sweat chloride concentration, growth percentiles, pulmonary-function values, chest-film score, pseudomonas colonization, nasal polyps, pancreatic sufficiency, pancreatitis, diabetes mellitus, meconium ileus, distal intestinal obstruction syndrome, rectal prolapse, cirrhosis, and gallbladder disease.

RESULTS

The compound heterozygotes having the genotype R117H/delta F508 clearly differed from the age- and sex-matched delta F508 homozygotes: they more often had pancreatic sufficiency (87 percent vs. 4 percent, P < 0.001), were older when the diagnosis was first made (mean [+/- SD] age, 10.2 +/- 10.5 vs. 2.5 +/- 4.3 years; P = 0.002), and had lower sweat chloride concentrations (80 +/- 18 vs. 108 +/- 14 mmol per liter, P < 0.001). There were no statistically significant differences between delta F508 homozygotes and other compound heterozygotes with regard to any variable tested.

CONCLUSIONS

Prenatal and prognostic counseling for patients with the R117H/delta F508 genotype should include the likelihood that they will have long-term pancreatic sufficiency. Patients with the other genotypes should expect the early onset of pancreatic insufficiency. For none of the genotypes studied can predictions be made about the occurrence of common complications or the severity or course of pulmonary disease.

Cystic fibrosis

The past few years have seen amazing progress in our understanding of the underlying cellular and molecular bases of CF. This new understanding has raised hopes for improved treatments in the very near future. These new treatments are expected to improve even further the prognosis for survival in this disorder, which has improved nearly 1 year for every passing year over the past two decades. The future for patients with CF is brighter than ever.