Accelerated lung function decline is a key COPD phenotype; however its genetic control remains largely unknown.
We performed a genome-wide association study using the Illumina Human660W-Quad v.1_A BeadChip. Generalized estimation equations were used to assess genetic contributions to lung function decline over a 5-year period in 4,048 European-American Lung Health Study participants with largely mild COPD. Genotype imputation was performed using reference HapMap II data. To validate regions meeting genome-wide significance, replication of top SNPs was attempted in independent cohorts. Three genes (TMEM26, ANK3 and FOXA1) within the regions of interest were selected for tissue expression studies using immunohistochemistry.
Measurements and Main Results
Two intergenic SNPs (rs10761570, rs7911302) on chromosome 10 and one SNP on chromosome 14 (rs177852) met genome-wide significance after Bonferroni. Further support for the chromosome 10 region was obtained by imputation, the most significantly associated imputed SNPs (rs10761571, rs7896712) being flanked by observed markers rs10761570 and rs7911302. Results were not replicated in four general population cohorts or a smaller cohort of subjects with moderate to severe COPD; however, we show novel expression of genes near regions of significantly associated SNPS, including TMEM26 and FOXA1 in airway epithelium and lung parenchyma, and ANK3 in alveolar macrophages. Levels of expression were associated with lung function and COPD status.
We identified two novel regions associated with lung function decline in mild COPD. Genes within these regions were expressed in relevant lung cells and their expression related to airflow limitation suggesting they may represent novel candidate genes for COPD susceptibility.
COPD; lung function decline; GWAS; genome wide association; genes; polymorphisms
A common promoter polymorphism (rs35705950) in MUC5B, the gene encoding mucin 5B, is associated with idiopathic pulmonary fibrosis. It is not known whether this polymorphism is associated with interstitial lung disease in the general population.
We performed a blinded assessment of interstitial lung abnormalities detected in 2633 participants in the Framingham Heart Study by means of volumetric chest computed tomography (CT). We evaluated the relationship between the abnormalities and the genotype at the rs35705950 locus.
Of the 2633 chest CT scans that were evaluated, interstitial lung abnormalities were present in 177 (7%). Participants with such abnormalities were more likely to have shortness of breath and chronic cough and reduced measures of total lung and diffusion capacity, as compared with participants without such abnormalities. After adjustment for covariates, for each copy of the minor rs35705950 allele, the odds of interstitial lung abnormalities were 2.8 times greater (95% confidence interval [CI], 2.0 to 3.9; P<0.001), and the odds of definite CT evidence of pulmonary fibrosis were 6.3 times greater (95% CI, 3.1 to 12.7; P<0.001). Although the evidence of an association between the MUC5B genotype and interstitial lung abnormalities was greater among participants who were older than 50 years of age, a history of cigarette smoking did not appear to influence the association.
The MUC5B promoter polymorphism was found to be associated with interstitial lung disease in the general population. Although this association was more apparent in older persons, it did not appear to be influenced by cigarette smoking. (Funded by the National Institutes of Health and others; ClinicalTrials.gov number, NCT00005121.)
Vitamin D is associated with lung health in epidemiologic studies, but mechanisms mediating observed associations are poorly understood. This study explores mechanisms for an effect of vitamin D in lung through an in vivo gene expression study, an expression quantitative trait loci (eQTL) analysis in lung tissue, and a population-based cohort study of sequence variants.
Microarray analysis investigated the association of gene expression in small airway epithelial cells with serum 25(OH)D in adult non-smokers. Sequence variants in candidate genes identified by the microarray were investigated in a lung tissue eQTL database, and also in relation to cross-sectional pulmonary function in the Health, Aging, and Body Composition (Health ABC) study, stratified by race, with replication in the Framingham Heart Study (FHS).
13 candidate genes had significant differences in expression by serum 25(OH)D (nominal p < 0.05), and a genome-wide significant eQTL association was detected for SGPP2. In Health ABC, SGPP2 SNPs were associated with FEV1 in both European- and African-Americans, and the gene-level association was replicated in European-American FHS participants. SNPs in 5 additional candidate genes (DAPK1, FSTL1, KAL1, KCNS3, and RSAD2) were associated with FEV1 in Health ABC participants.
SGPP2, a sphingosine-1-phosphate phosphatase, is a novel vitamin D-responsive gene associated with lung function. The identified associations will need to be followed up in further studies.
Vitamin D; Airflow obstruction; FEV1; SGPP2; FEV1/FVC
Genome-wide association studies (GWAS) have identified determinants of chronic obstructive pulmonary disease, asthma and lung function level, however none addressed decline in lung function.
We conducted the first GWAS on age-related decline in forced expiratory volume in the first second (FEV1) and in its ratio to forced vital capacity (FVC) stratified a priori by asthma status.
Discovery cohorts included adults of European ancestry (1441 asthmatics, 2677 non-asthmatics; Epidemiological Study on the Genetics and Environment of Asthma (EGEA); Swiss Cohort Study on Air Pollution And Lung And Heart Disease In Adults (SAPALDIA); European Community Respiratory Health Survey (ECRHS)). The associations of FEV1 and FEV1/FVC decline with 2.5 million single nucleotide polymorphisms (SNPs) were estimated. Thirty loci were followed-up by in silico replication (1160 asthmatics, 10858 non-asthmatics: Atherosclerosis Risk in Communities (ARIC); Framingham Heart Study (FHS); British 1958 Birth Cohort (B58C); Dutch asthma study).
Main signals identified differed between asthmatics and non-asthmatics. None of the SNPs reached genome-wide significance. The association between the height related gene DLEU7 and FEV1 decline suggested for non-asthmatics in the discovery phase was replicated (discovery P=4.8×10−6; replication P=0.03) and additional sensitivity analyses point to a relation to growth. The top ranking signal, TUSC3, associated with FEV1/FVC decline in asthmatics (P=5.3×10−8) did not replicate. SNPs previously associated with cross-sectional lung function were not prominently associated with decline.
Genetic heterogeneity of lung function may be extensive. Our results suggest that genetic determinants of longitudinal and cross-sectional lung function differ and vary by asthma status.
Asthma; cohort studies; genome-wide association; lung function decline; heterogeneity
Atopy and plasma IgE concentration are genetically complex traits, and the specific genetic risk factors that lead to IgE dysregulation and clinical atopy are an area of active investigation.
To ascertain the genetic risk factors which lead to IgE dysregulation.
A genome wide association study (GWAS) was performed in 6,819 participants from the Framingham Heart Study (FHS). Seventy of the top SNPs were selected based on p-values and linkage disequilibrium among neighboring SNPs and evaluated in a meta-analysis with five independent populations from the KORA, B58C, and CAMP cohorts.
Thirteen SNPs located in the region of three genes, FCER1A, STAT6, and IL-13, were found to have genome-wide significance in the FHS GWAS. The most significant SNPs from the three regions were rs2251746 (FCER1A, p-value 2.11×10-12), rs1059513 (STAT6, p-value 2.87×10-08), and rs1295686 (IL-13, p-value 3.55×10-08). Four additional gene regions - HLA-G, HLA-DQA2, HLA-A, and DARC - reached genome-wide statistical significance in meta-analysis combining FHS and replication cohorts, although the DARC association did not appear independent of SNPs in the nearby FCER1A gene.
This GWAS of the FHS has identified genetic loci in HLA genes that may have a role in the pathogenesis of IgE dysregulation and atopy. It also confirmed the association of known susceptibility loci, FCER1A, STAT6, and IL-13, for the dysregulation of total IgE.
total IgE; atopy; asthma; GWAS
Soluble ST2 (sST2) is a cardiac biomarker whose concentration rises in response to myocardial strain. Increased sST2 concentrations may predict adverse outcomes in patients with heart failure and myocardial infarction. Because sST2 was largely undetectable with first-generation assays in ambulatory individuals, there are few data regarding its distribution and correlates in community-based populations.
We measured sST2 using a highly sensitive ELISA in 3450 Framingham Heart Study participants who attended a routine examination. We used multivariable linear regression models to identify covariates associated with sST2 in the general sample. We obtained a reference sample (n = 1136) by excluding individuals with prevalent coronary disease, heart failure, atrial fibrillation, diabetes, hypertension, obesity, valvular disease, left ventricular systolic dysfunction, and pulmonary and renal dysfunction. We used empiric and quantile regression techniques to estimate the 2.5th, 50th, 97.5th, and 99th quantiles.
In the general sample (mean age 59 years, 55% women), systolic blood pressure (P = 0.006), antihypertensive medication use (P = 0.03), and diabetes (P < 0.001) were associated with sST2 concentrations. In the reference sample (mean age 55, 59% women), male sex (P < 0.0001) and older age (P = 0.004) were predictive of higher sST2 concentrations. Quantile and empirical methods were used to define the reference intervals. Using the empirical approach, upper 99% percentile values in different age groups ranged from 46.6 to 64.4 μg/L in men and 36.7 to 53.0 μg/L in women.
In a well-characterized, community-based cohort, values for sST2 differ between men and women, increase with age, and are associated with diabetes and hypertension.
To develop and test a prototype dyspnea computer adaptive test.
Two outpatient medical facilities.
A convenience sample of 292 adults with COPD.
Main Outcome Measure
We developed a modified and expanded item bank and computer adaptive test (CAT) for the Dyspnea Management Questionnaire (DMQ), an outcome measure consisting of four dyspnea dimensions: dyspnea intensity, dyspnea anxiety, activity avoidance, and activity self-efficacy.
Factor analyses supported a four-dimensional model underlying the 71 DMQ items. The DMQ item bank achieved acceptable Rasch model fit statistics, good measurement breadth with minimal floor and ceiling effects, and evidence of high internal consistency reliability (α = 0.92 to 0.98). Using CAT simulation analyses, the DMQ-CAT showed high measurement accuracy compared to the total item pool (r = .83 to .97, p < .0001) and evidence of good to excellent concurrent (r = −.61 to −0.80, p < .0001) validity. All DMQ-CAT domains showed evidence for known-groups validity (p ≤ 0.001).
The DMQ-CAT reliably and validly captured four distinct dyspnea domains. Multidimensional dyspnea assessment in COPD is needed to better measure the effectiveness of pharmacologic, pulmonary rehabilitation, and psychosocial interventions in not only alleviating the somatic sensation of dyspnea but also reducing dysfunctional emotions, cognitions, and behaviors associated with dyspnea, especially for anxious patients.
Dyspnea; COPD; Outcomes assessment; Reliability; Validity
Recent studies have reported conflicting data on the association between maternal intake of vitamin D during pregnancy and asthma.
Assess the influence of prenatal vitamin D status on immune function at birth.
In an inner-city birth cohort of 568 newborns, 520 of whom had at least one atopic parent, we measured umbilical cord (UC) plasma concentration of 25-hydroxy vitamin D (25(OH)D) and the cytokine responses of UC blood mononuclear cells (UCMCs) to stimuli including phytohemaglutinin (PHA), lipopolysaccharide (LPS), and peptidoglycan (PG). In a subset, UCMC expression of regulatory T-cell markers and the suppressive activity of CD4+CD25+ UCMCs was measured.
The 25th, 50th, and 75th percentiles of UC plasma 25(OH)D level were 15.0, 20.2, and 25.6 ng/mL, respectively. Most cytokine responses of UCMC were not correlated with UC 25(OH)D concentration; however, IFN-γ release after LPS stimulation was weakly positively correlated with UC 25(OH)D concentration (r = 0.11, p =0.01). PHA responses were not significantly correlated with 25(OH)D concentration. The UC plasma 25(OH)D concentration was inversely related to the number of CD25+ (r= -0.20, p=0.06), CD25Bright (r= -0.21, p=0.05), and CD25+FoxP3 (r= -0.29, p=0.06) cells as a proportion of CD4+ T cells in UC blood (r = -0.26, p = 0.04) but not to the suppressive activity of CD4+CD25+ cells (r=0.17, p=0.22).
Conclusion and Clinical Relevance
UC 25(OH)D concentration was not correlated with most UCMC cytokine responses to multiple stimuli. There was a suggestion of a weakly positive correlation with IFN-γ release after LPS stimulation. The proportions of CD25+, CD25bright, and CD25+FoxP3 cells to total CD4+ T cells were inversely correlated with UC 25(OH)D concentration. Our findings suggest that higher vitamin D levels at birth may be associated with a lower number of T regulatory cells. Vitamin D status in utero may influence immune regulation in early life.
Endogenous carbon monoxide (CO) at physiologic concentrations is cytoprotective, whereas excess levels reflect underlying oxidative stress, inflammation, and vascular pathology and portend adverse clinical sequelae. However, the relation of exhaled CO to metabolic/vascular risk in the community is unknown.
Methods and Results
We related exhaled CO, a surrogate measure of blood CO concentration, to the risk of developing new-onset metabolic syndrome and incident cardiovascular disease (CVD) following 14,943 routine examinations (4,139 unique participants; mean age 46 years, 53% women) in the Framingham Heart Study. Baseline exhaled CO was associated with the presence of cardiometabolic risk factors (including smoking) and prevalent metabolic syndrome (odds ratio [OR] 1.08 per log-CO; 95% confidence interval [CI] 1.02–1.16; P=0.01). During up to 4 years of follow up, 1,458 participants developed new-onset metabolic syndrome, and 416 experienced a first CVD event. Compared to individuals in the lowest quartile of exhaled CO, those in the highest quartile were more likely to develop metabolic syndrome (OR 1.48, 95% CI 1.25–1.76; P<0.0001) and CVD events (hazards ratio 1.66, 95% CI 1.14–2.40; P=0.008) in multivariable analyses that included adjustment for smoking status.
In our community-based sample, higher exhaled CO levels predicted the development of metabolic syndrome and future CVD events, underscoring the importance of this endogenous second messenger in the pathogenesis of metabolic and vascular risk.
carbon monoxide; risk factors; metabolic syndrome; cardiovascular disease
Rationale: Sleep-disordered breathing (SDB), the recurrent episodic disruption of normal breathing during sleep, affects as much as 17% of U.S. adults, and may be more prevalent in poor urban environments. SDB and air pollution have been linked to increased cardiovascular diseases and mortality, but the association between pollution and SDB is poorly understood.
Objectives: We used data from the Sleep Heart Health Study (SHHS), a U.S. multicenter cohort study assessing cardiovascular and other consequences of SDB, to examine whether particulate air matter less than 10 μm in aerodynamic diameter (PM10) was associated with SDB among persons 39 years of age and older.
Methods: Using baseline data from SHHS urban sites, outcomes included the following: the respiratory disturbance index (RDI); percentage of sleep time at less than 90% O2 saturation; and sleep efficiency, measured by overnight in-home polysomnography. We applied a fixed-effect model containing a city effect, controlling for potential predictors. In all models we included both the 365-day moving averages of PM10 and temperature (long-term effects) and the differences between the daily measures of these two predictors and their 365-day average (short-term effects).
Measurements and Main Results: In summer, increases in RDI or percentage of sleep time at less than 90% O2 saturation, and decreases in sleep efficiency, were all associated with increases in short-term variation in PM10. Over all seasons, we found that increased RDI was associated with an 11.5% (95% confidence interval: 1.96, 22.01) increase per interquartile range increase (25.5°F) in temperature.
Conclusions: Reduction in air pollution exposure may decrease the severity of SDB and nocturnal hypoxemia and may improve cardiac risk.
particulate matter; sleep-disordered breathing; sleep architecture
Clinic-based observational studies in men have reported that obstructive sleep apnea (OSA) is associated with an increased incidence of coronary heart disease. The objective of this study was to assess the relation of OSA to incident coronary heart disease and heart failure in a general community sample of adult men and women.
Methods and Results
A prospective, longitudinal epidemiologic study of 1927 men and 2495 women aged ≥ 40 years and free of coronary heart disease and heart failure at the time of baseline polysomnography were followed for a median of 8.7 years. After adjustment for multiple risk factors, OSA was a significant predictor of incident coronary heart disease (myocardial infarction, revascularization procedure, or coronary heart disease death) only in men age ≤70 years (adjusted hazard ratio 1.10 [95% CI 1.00, 1.21] per 10-unit increase in apnea-hypopnea index [AHI]), but not in older men or in women of any age. Among men age 40–70 years, those with AHI ≥30 were 68% more likely to develop coronary heart disease than those with AHI <5. OSA predicted incident heart failure in men but not in women (adjusted hazard ratio 1.13 [95% CI 1.02, 1.26] per 10-unit increase in AHI). Men with AHI ≥30 were 58% more likely to develop heart failure than those with AHI <5.
OSA is associated with increased risk of incident heart failure in community-dwelling middle-aged and older men; its association with incident coronary heart disease in this sample is equivocal.
epidemiology; sleep apnea; coronary disease; heart failure
Rationale: Although obstructive sleep apnea is associated with physiological perturbations that increase risk of hypertension and are proatherogenic, it is uncertain whether sleep apnea is associated with increased stroke risk in the general population.
Objectives: To quantify the incidence of ischemic stroke with sleep apnea in a community-based sample of men and women across a wide range of sleep apnea.
Methods: Baseline polysomnography was performed between 1995 and 1998 in a longitudinal cohort study. The primary exposure was the obstructive apnea–hypopnea index (OAHI) and outcome was incident ischemic stroke.
Measurements and Main Results: A total of 5,422 participants without a history of stroke at the baseline examination and untreated for sleep apnea were followed for a median of 8.7 years. One hundred ninety-three ischemic strokes were observed. In covariate-adjusted Cox proportional hazard models, a significant positive association between ischemic stroke and OAHI was observed in men (P value for linear trend: P = 0.016). Men in the highest OAHI quartile (>19) had an adjusted hazard ratio of 2.86 (95% confidence interval, 1.1–7.4). In the mild to moderate range (OAHI, 5–25), each one-unit increase in OAHI in men was estimated to increase stroke risk by 6% (95% confidence interval, 2–10%). In women, stroke was not significantly associated with OAHI quartiles, but increased risk was observed at an OAHI greater than 25.
Conclusions: The strong adjusted association between ischemic stroke and OAHI in community-dwelling men with mild to moderate sleep apnea suggests that this is an appropriate target for future stroke prevention trials.
sleep apnea; stroke; epidemiology
Asthmatics exhibit reduced airway dilation at maximal inspiration, likely due to structural differences in airway walls and/or functional differences in airway smooth muscle, factors that may also increase airway responsiveness to bronchoconstricting stimuli. The goal of this study was to test the hypothesis that the minimal airway resistance achievable during a maximal inspiration (Rmin) is abnormally elevated in subjects with airway hyperresponsiveness.
The Rmin was measured in 34 nonasthmatic and 35 asthmatic subjects using forced oscillations at 8 Hz. Rmin and spirometric indices were measured before and after bronchodilation (albuterol) and bronchoconstriction (methacholine). A preliminary study of 84 healthy subjects first established height dependence of baseline Rmin values.
Asthmatics had a higher baseline Rmin % predicted than nonasthmatic subjects (134 ± 33 vs. 109 ± 19 % predicted, p = 0.0004). Sensitivity-specificity analysis using receiver operating characteristic curves indicated that baseline Rmin was able to identify subjects with airway hyperresponsiveness (PC20 < 16 mg/mL) better than most spirometric indices (Area under curve = 0.85, 0.78, and 0.87 for Rmin % predicted, FEV1 % predicted, and FEF25-75 % predicted, respectively). Also, 80% of the subjects with baseline Rmin < 100% predicted did not have airway hyperresponsiveness while 100% of subjects with Rmin > 145% predicted had hyperresponsive airways, regardless of clinical classification as asthmatic or nonasthmatic.
These findings suggest that baseline Rmin, a measurement that is easier to perform than spirometry, performs as well as or better than standard spirometric indices in distinguishing subjects with airway hyperresponsiveness from those without hyperresponsive airways. The relationship of baseline Rmin to asthma and airway hyperresponsiveness likely reflects a causal relation between conditions that stiffen airway walls and hyperresponsiveness. In conjunction with symptom history, Rmin could provide a clinically useful tool for assessing asthma and monitoring response to treatment.
Allergic rhinitis (AR) affects up to 80% of children with asthma and increases asthma severity. Thymic stromal lymphopoietin (TSLP) is a key mediator of allergic inflammation. The role of the TSLP gene (TSLP) in the pathogenesis of AR has not been studied.
To test for associations between variants in TSLP, TSLP-related genes, and AR in children with asthma.
We genotyped 15 single nucleotide polymorphisms (SNPs) in TSLP, OX40L, IL7R, and RXRα in three independent cohorts: 592 asthmatic Costa Rican children and their parents, 422 nuclear families of North American children with asthma, and 239 Swedish children with asthma. We tested for associations between these SNPs and AR. As we previously reported sex-specific effects for TSLP, we performed overall and sex-stratified analyses. We additionally performed secondary analyses for gene-by-gene interactions.
Across the three cohorts, the T allele of TSLP SNP rs1837253 was undertransmitted in boys with AR and asthma as compared to boys with asthma alone. The SNP was associated with reduced odds for AR (odds ratios ranging from 0.56 to 0.63, with corresponding Fisher's combined P value of 1.2 × 10-4). Our findings were significant after accounting for multiple comparisons. SNPs in OX40L, IL7R, and RXRα were not consistently associated with AR in children with asthma. There were nominally significant interactions between gene pairs.
TSLP SNP rs1837253 is associated with reduced odds for AR in boys with asthma. Our findings support a role for TSLP in the pathogenesis of AR in children with asthma.
Single nucleotide polymorphisms (SNPs) in thymic stromal lymphopoietin (TSLP) have been associated with IgE (in girls) and asthma (in general). We sought to determine whether TSLP SNPs are associated with asthma in a sex-specific fashion.
We conducted regular and sex-stratified analyses of association between SNPs in TSLP and asthma in families of asthmatic children in Costa Rica. Significant findings were replicated in white and African-American participants in the Childhood Asthma Management Program, in African Americans in the Genomic Research on Asthma in the African Diaspora study, in whites and Hispanics in the Children’s Health Study, and in whites in the Framingham Heart Study (FHS).
Two SNPs in TSLP (rs1837253 and rs2289276) were significantly associated with a reduced risk of asthma in combined analyses of all cohorts (p values of 2×10−5 and 1×10−5, respectively). In a sex-stratified analysis, the T allele of rs1837253 was significantly associated with a reduced risk of asthma in males only (p= 3×10−6). Alternately, the T allele of rs2289276 was significantly associated with a reduced risk of asthma in females only (p= 2×10−4). Findings for rs2289276 were consistent in all cohorts except the FHS.
TSLP variants are associated with asthma in a sex-specific fashion.
asthma; genetic association; sex-specific; thymic stromal lymphopoietin; TSLP
Immunologic responses at birth likely relate to subsequent risks for allergic diseases and wheezing in infancy; however, the influences of parental characteristics and prenatal factors on neonatal immune responses are incompletely understood.
This study investigates potential correlations between urban parental, prenatal and perinatal factors on innate and adaptive stimuli-induced cytokine responses.
560 and 49 children of parents with and without allergic disease or asthma, respectively, were enrolled into a prospective birth cohort study (Urban Environment and Childhood Asthma [URECA]). Cord blood mononuclear cells were incubated with innate and adaptive immune stimuli, and cytokine responses (ELISA) were compared to season of birth, parental characteristics, in-utero stressors, and fetal growth.
Many cytokine responses varied by season of birth, including 2–3 fold fluctuations with specific IFN-α and IFN-γ responses. Birthweight was inversely associated with IFN-γ responses to RSV (R=−0.16), but positively associated with IL-8 responses to a variety of innate stimuli (R=0.08–0.12). Respiratory syncytial virus (RSV) induced cytokine responses were 21–54% lower in children of mothers with asthma. Cytokine responses were generally lower in babies born to parents with allergy/asthma.
Innate cytokine responses are associated with parental allergic or airway disease, somatic fetal growth, ethnicity, and season of birth. Collectively, these findings suggest that urban prenatal exposures and familial factors affect the development of the fetal immune system.
Prenatal influences that disturb normal immune development might establish the patterns that are associated with recurrent wheezing in infants and preschoolers, and later as allergy and asthma in school-age children.
Atopy; immune response; cord blood; birth cohort; gestational age; cytokines
Clinic-based case-control studies linked sleep-disordered breathing (SDB) to markers of endothelial dysfunction. We attempted to validate this association in a large community-based sample, and evaluate the relation of SDB to arterial diameter and peripheral blood flow. This community-based cross-sectional observational study included 327 men and 355 women, age 42 to 83 years, from the Framingham Heart Study site of the Sleep Heart Health Study. Polysomnographically derived apnea-hypopnea index and hypoxemia index (percent sleep time with oxyhemoglobin saturation below 90%) were used to quantify the severity of SDB. Brachial artery ultrasound measurements included baseline diameter, percent flow-mediated dilation, and baseline and hyperemic flow velocity and volume. Baseline brachial artery diameter was significantly associated with both apnea-hypopnea index and hypoxemia index. The association was diminished by adjustment for body mass index, but remained significant for apnea-hypopnea index. Age-, sex-, race-and body mass index-adjusted mean diameters were 4.32, 4.33, 4.33, 4.56, 4.53 mm, respectively, for those with apnea-hypopnea index <1.5, 1.5–4.9, 5–14.9, 15–29.9, ≥30; p=0.03. Baseline flow measures were associated with apnea-hypopnea index but this association was non-significant after adjusting for body mass index. No significant association was observed between measures of SDB and percent flow-mediated dilation or hyperemic flow in any model. In conclusion, this study supports a moderate association of SDB and larger baseline brachial artery diameter, which may reflect SDB-induced vascular remodeling. This study does not support a link between SDB and endothelial dysfunction as measured by brachial artery flow-mediated dilation.
Sleep Apnea; Obstructive; Endothelium; Vascular; Remodeling; Vascular; Epidemiology
Asthma is a chronic respiratory disease whose genetic basis has been explored for over two decades, most recently via genome-wide association studies. We sought to find asthma-susceptibility variants by using probands from a single population in both family-based and case-control association designs.
We used probands from the Childhood Asthma Management Program (CAMP) in two primary genome-wide association study designs: (1) probands were combined with publicly available population controls in a case-control design, and (2) probands and their parents were used in a family-based design. We followed a two-stage replication process utilizing three independent populations to validate our primary findings.
We found that single nucleotide polymorphisms with similar case-control and family-based association results were more likely to replicate in the independent populations, than those with the smallest p-values in either the case-control or family-based design alone. The single nucleotide polymorphism that showed the strongest evidence for association to asthma was rs17572584, which replicated in 2/3 independent populations with an overall p-value among replication populations of 3.5E-05. This variant is near a gene that encodes an enzyme that has been implicated to act coordinately with modulators of Th2 cell differentiation and is expressed in human lung.
Our results suggest that using probands from family-based studies in case-control designs, and combining results of both family-based and case-control approaches, may be a way to augment our ability to find SNPs associated with asthma and other complex diseases.
Rationale: Cross-sectional epidemiologic studies show an association between sleep-disordered breathing and hypertension, but only one cohort study has examined sleep-disordered breathing as a risk factor for incident hypertension.
Objectives: To examine whether sleep-disordered breathing increases the risk of incident hypertension among persons 40 years of age and older.
Methods: In a prospective cohort study, we analyzed data from 2,470 participants who at baseline did not have hypertension, defined as blood pressure of at least 140/90 mm Hg or taking antihypertensive medication. The apnea-hypopnea index (AHI), the number of apneas plus hypopneas per hour of sleep, was measured by overnight in-home polysomnography. We estimated odds ratios for developing hypertension during 5 years of follow-up according to baseline AHI.
Measurements and Main Results: The odds ratios for incident hypertension increased with increasing baseline AHI; however, this relationship was attenuated and not statistically significant after adjustment for baseline body-mass index. Although not statistically significant, the observed association between a baseline AHI greater than 30 and future hypertension (odds ratio, 1.51; 95% confidence interval, 0.93–2.47) does not exclude the possibility of a modest association.
Conclusions: Among middle-aged and older persons without hypertension, much of the relationship between AHI and risk of incident hypertension was accounted for by obesity. After adjustment for body mass index, the AHI was not a significant predictor of future hypertension, although a modest influence of an AHI greater than 30 on hypertension could not be excluded.
sleep apnea; sleep-disordered breathing; hypertension; cohort study
Measurements of lung function by spirometry are heritable traits that reflect respiratory health and predict morbidity and mortality. We meta-analyzed genome-wide association studies for two clinically important measures, forced expiratory volume in the first second (FEV1) and its ratio to forced vital capacity (FEV1/FVC), an indicator of airflow obstruction. This meta-analysis included 20,890 participants of European ancestry from four CHARGE consortium studies: Atherosclerosis Risk in Communities (ARIC), Cardiovascular Health Study (CHS), Framingham Heart Study (FHS), and Rotterdam Study (RS). We identified eight loci associated with FEV1/FVC (HHIP, GPR126, ADAM19, AGER-PPT2, FAM13A, PTCH1, PID1, and HTR4) and one locus associated with FEV1 (INTS12-GSTCD-NPNT) at or near genome-wide significance (P<5×10−8) in CHARGE; all but 3 loci (FAM13A, PTCH1, and PID1) replicated with the SpiroMeta consortium. Our findings of novel loci influencing pulmonary function may offer insights into chronic lung disease pathogenesis.
Evidence from prospective studies consistently links obesity to asthma onset in white women, although there is controversy as to whether the association is causal. There are few data on this topic in black women, among whom the prevalence of obesity and asthma is high.
We prospectively assessed the relation of body mass index (BMI) to asthma incidence in the Black Women’s Health Study.
We followed 46,435 women from 1995 through 2005 with biennial mailed questionnaires. Cox regression models were used to estimate incidence rate ratios and 95% CIs.
During 403,394 person-years of follow-up, 1068 participants reported physician-diagnosed asthma and concurrent use of asthma medication. Compared with women with BMIs of 20 to 24, the multivariate incidence rate ratios for higher categories of BMI increased from 1.26 (95% CI, 1.05–1.51) for BMIs of 25 to 29 to 2.85 (95% CI, 2.19–3.72) for BMIs of 40 or greater, with a significant trend. The association of BMI with asthma risk was consistent across strata of smoking status, age, presence of sleep apnea, parental history of asthma, BMI at age 18 years, and energy expenditure and intake.
In this large cohort of African American women, there was a positive association between BMI and asthma risk that was similar in magnitude to those observed in longitudinal studies of white women. (J Allergy Clin Immunol 2009;123:89–95.)
Asthma; body mass index; cohort studies; African Americans; incidence; longitudinal studies
For genome-wide association studies in family-based designs, we propose a new, universally applicable approach. The new test statistic exploits all available information about the association, while, by virtue of its design, it maintains the same robustness against population admixture as traditional family-based approaches that are based exclusively on the within-family information. The approach is suitable for the analysis of almost any trait type, e.g. binary, continuous, time-to-onset, multivariate, etc., and combinations of those. We use simulation studies to verify all theoretically derived properties of the approach, estimate its power, and compare it with other standard approaches. We illustrate the practical implications of the new analysis method by an application to a lung-function phenotype, forced expiratory volume in one second (FEV1) in 4 genome-wide association studies.
In genome-wide association studies, the multiple testing problem and confounding due to population stratification have been intractable issues. Family-based designs have considered only the transmission of genotypes from founder to nonfounder to prevent sensitivity to the population stratification, which leads to the loss of information. Here we propose a novel analysis approach that combines mutually independent FBAT and screening statistics in a robust way. The proposed method is more powerful than any other, while it preserves the complete robustness of family-based association tests, which only achieves much smaller power level. Furthermore, the proposed method is virtually as powerful as population-based approaches/designs, even in the absence of population stratification. By nature of the proposed method, it is always robust as long as FBAT is valid, and the proposed method achieves the optimal efficiency if our linear model for screening test reasonably explains the observed data in terms of covariance structure and population admixture. We illustrate the practical relevance of the approach by an application in 4 genome-wide association studies.
The major marker utilized to monitor COPD patients is forced expiratory volume in one second (FEV1). However, asingle measurement of FEV1 cannot reliably predict subsequent decline. Recent studies indicate that T lymphocytes and eosinophils are important determinants of disease stability in COPD. We therefore measured cytokine levels in the lung lavage fluid and plasma of COPD patients in order to determine if the levels of T cell or eosinophil related cytokines were predictive of the future course of the disease.
Baseline lung lavage and plasma samples were collected from COPD subjects with moderately severe airway obstruction and emphysematous changes on chest CT. The study participants were former smokers who had not had a disease exacerbation within the past six months or used steroids within the past two months. Those subjects who demonstrated stable disease over the following six months (ΔFEV1 % predicted = 4.7 ± 7.2; N = 34) were retrospectively compared with study participants who experienced a rapid decline in lung function (ΔFEV1 % predicted = -16.0 ± 6.0; N = 16) during the same time period and with normal controls (N = 11). Plasma and lung lavage cytokines were measured from clinical samples using the Luminex multiplex kit which enabled the simultaneous measurement of several T cell and eosinophil related cytokines.
Results and Discussion
Stable COPD participants had significantly higher plasma IL-2 levels compared to participants with rapidly progressive COPD (p = 0.04). In contrast, plasma eotaxin-1 levels were significantly lower in stable COPD subjects compared to normal controls (p < 0.03). In addition, lung lavage eotaxin-1 levels were significantly higher in rapidly progressive COPD participants compared to both normal controls (p < 0.02) and stable COPD participants (p < 0.05).
These findings indicate that IL-2 and eotaxin-1 levels may be important markers of disease stability in advanced emphysema patients. Prospective studies will need to confirm whether measuring IL-2 or eotaxin-1 can identify patients at risk for rapid disease progression.
Preliminary evidence is equivocal regarding the role of exhaled nitric oxide in clinical asthma management. This study evaluates the usefulness of eNO as an adjunct to asthma guidelines-based clinical care among inner-city adolescents and young adults.
A randomized, double-blind, parallel-group trial was conducted with 546 inner-city participants, aged 12–20 years, with persistent asthma (Clinicaltrials.gov Identifier: NCT00114413). A run-in characterization period of 3 weeks on an initial controller regimen preceded a 46-week double-blind treatment strategy. Participants were randomized to either, treatment based on NAEPP guidelines alone (Reference Group) or the guidelines plus FENO measurements (FENO Group). Primary outcome was asthma symptom days and secondary outcome was acute asthma exacerbations.
During the 46-week treatment period, the number of asthma symptom days, pulmonary function, unscheduled care visits, and hospitalizations did not differ between the treatment groups (mean asthma symptom days were 1.93 [95% CI 1.74-2.11] in the FENO group vs. 1.89 [1.71-1.74] in the control group; difference 0.04 [-0.29-0.22], p=0.7796). The FENO Group received a significantly higher inhaled corticosteroid dose (118.9 mcg/day difference, 95% CI: 48.5-189.3, P=0.0010) as compared to the Reference Group. Asthma symptoms remained low in both groups following randomization with 57% (306/534) of the participants well controlled for at least 80% of visits..
A coordinated asthma management program facilitated achieving good control in the majority of participants. The addition of FENO as a control indicator resulted in a higher dose of inhaled corticosteroids without a clinically important improvement in symptomatic asthma control.
asthma; biomarker; exhaled nitric oxide; inhaled corticosteroid; inner-city asthma; long-acting ß2-agonist; medication adherence; asthma exacerbations; asthma outcomes; asthma guidelines; impairment; risk