Rationale: Pulmonary emphysema overlaps partially with spirometrically defined chronic obstructive pulmonary disease and is heritable, with moderately high familial clustering.
Objectives: To complete a genome-wide association study (GWAS) for the percentage of emphysema-like lung on computed tomography in the Multi-Ethnic Study of Atherosclerosis (MESA) Lung/SNP Health Association Resource (SHARe) Study, a large, population-based cohort in the United States.
Methods: We determined percent emphysema and upper-lower lobe ratio in emphysema defined by lung regions less than −950 HU on cardiac scans. Genetic analyses were reported combined across four race/ethnic groups: non-Hispanic white (n = 2,587), African American (n = 2,510), Hispanic (n = 2,113), and Chinese (n = 704) and stratified by race and ethnicity.
Measurements and Main Results: Among 7,914 participants, we identified regions at genome-wide significance for percent emphysema in or near SNRPF (rs7957346; P = 2.2 × 10−8) and PPT2 (rs10947233; P = 3.2 × 10−8), both of which replicated in an additional 6,023 individuals of European ancestry. Both single-nucleotide polymorphisms were previously implicated as genes influencing lung function, and analyses including lung function revealed independent associations for percent emphysema. Among Hispanics, we identified a genetic locus for upper-lower lobe ratio near the α-mannosidase–related gene MAN2B1 (rs10411619; P = 1.1 × 10−9; minor allele frequency [MAF], 4.4%). Among Chinese, we identified single-nucleotide polymorphisms associated with upper-lower lobe ratio near DHX15 (rs7698250; P = 1.8 × 10−10; MAF, 2.7%) and MGAT5B (rs7221059; P = 2.7 × 10−8; MAF, 2.6%), which acts on α-linked mannose. Among African Americans, a locus near a third α-mannosidase–related gene, MAN1C1 (rs12130495; P = 9.9 × 10−6; MAF, 13.3%) was associated with percent emphysema.
Conclusions: Our results suggest that some genes previously identified as influencing lung function are independently associated with emphysema rather than lung function, and that genes related to α-mannosidase may influence risk of emphysema.
emphysema; computed tomography; multiethnic; cohort study; genetic association
Pulmonary emphysema is divided into three major subtypes at autopsy: centrilobular, paraseptal and panlobular emphysema. These subtypes can be defined by visual assessment on computed tomography (CT); however, clinical characteristics of emphysema subtypes on CT are not well-defined. We developed a reliable approach to visual assessment of emphysema subtypes on CT and examined if emphysema subtypes have distinct characteristics.
The Multi-Ethnic Study of Atherosclerosis COPD Study recruited smokers with COPD and controls age 50–79 years with ≥10 pack-years. Participants underwent CT following a standardized protocol. Definitions of centrilobular, paraseptal and panlobular emphysema were obtained by literature review. Six-minute walk distance and pulmonary function were performed following guidelines.
Twenty-seven percent of 318 smokers had emphysema on CT. Inter-rater reliability of emphysema subtype was substantial (K:0.70). Compared to participants without emphysema, individuals with centrilobular or panlobular emphysema had greater dyspnea, reduced walk distance, greater hyperinflation, and lower diffusing capacity. In contrast, individuals with PSE were similar to controls, except for male predominance. Centrilobular but not panlobular or paraseptal emphysema was associated with greater smoking history (+21 pack-years P<0.001). Panlobular but not other types of emphysema was associated with reduced body mass index (−5 kg/m2;P=0.01). Other than for dyspnea, these findings were independent of the forced expiratory volume in one second. Seventeen percent of smokers without COPD on spirometry had emphysema, which was independently associated with reduced walk distance.
Emphysema subtypes on CT are common in smokers with and without COPD. Centrilobular and panlobular emphysema but not paraseptal emphysema have considerable symptomatic and physiological consequences.
Emphysema; computed tomography; centrilobular; paraseptal; panlobular
Quantitative computed tomography (QCT) can provide reliable and valid measures of lung structure and volumes. Similar to lung function and volumes measured by spirometry, lung measures obtained by QCT vary by demographic and anthropomorphic factors including sex, race/ethnicity and height in asymptomatic non-smokers. Hence, some accounting for these factors is necessary to define abnormal from normal QCT values and disease severity. Similar to spirometry and cardiac volumes, prediction equations for QCT may be derived from a sample of asymptomatic individuals to estimate reference values.
This paper describes the methodology of reference equation development using, as an example, quantitative densitometry to detect pulmonary emphysema. The process described is generalizable to other QCT measures, including lung volumes, airway dimensions and gas-trapping. Pulmonary emphysema is defined morphologically by airspace enlargement with alveolar wall destruction and has been shown to correlate with low lung attenuation estimated by QCT. Deriving reference values for a normal quantity of low lung attenuation requires three steps: First, criteria that define normal must be established. Second, variables for inclusion must be selected based on an understanding of subject, scanner and protocol specific factors that influence lung attenuation. Finally, a reference sample of normal individuals must be selected that is representative of the population in which QCT will be used to detect pulmonary emphysema. Sources of bias and confounding inherent to reference values are also discussed.
Reference equation development is a multistep process that can define normal values for QCT measures such as lung attenuation. Normative reference values will increase the utility of QCT in both research and clinical practice.
quantitative; computed tomography; emphysema; reference equation; prediction
Whether African Americans (AA) are more susceptible to COPD than non-Hispanic Whites (NHW) and whether racial differences in disease phenotype exist is controversial. The objective is to determine racial differences in the extent of emphysema and airway remodeling in COPD.
First, 2,500 subjects enrolled in the COPDGene study were used to evaluate racial differences in quantitative CT (QCT) parameters of % emphysema, air trapping and airway wall thickness. Independent variables studied included race, age, gender, education, BMI, pack-years, smoking status, age at smoking initiation, asthma, previous work in dusty job, CT scanner and center of recruitment.
Of the 1,063 subjects with GOLD Stage II-IV COPD, 200 self-reported as AA. AAs had a lower mean % emphysema (13.1 % vs. 16.1%, p = 0.005) than NHW and proportionately less emphysema in the lower lung zones. After adjustment for covariates, there was no statistical difference by race in air trapping or airway wall thickness. Measured QCT parameters were more predictive of poor functional status in NHWs compared to AAs.
AAs have less emphysema than NHWs but the same degree of airway disease. Additional factors not easily assessed by current QCT techniques may account for the poor functional status in AAs.
Airway wall thickness; Air trapping; Chronic obstructive pulmonary disease; Emphysema; Quantitative CT; Race
Background: Air pollution is linked to low lung function and to respiratory events, yet little is known of associations with lung structure.
Objectives: We examined associations of particulate matter (PM2.5, PM10) and nitrogen oxides (NOx) with percent emphysema-like lung on computed tomography (CT).
Methods: The Multi-Ethnic Study of Atherosclerosis (MESA) recruited participants (45–84 years of age) in six U.S. states. Percent emphysema was defined as lung regions < –910 Hounsfield Units on cardiac CT scans acquired following a highly standardized protocol. Spirometry was also conducted on a subset. Individual-level 1- and 20-year average air pollution exposures were estimated using spatiotemporal models that included cohort-specific measurements. Multivariable regression was conducted to adjust for traditional risk factors and study location.
Results: Among 6,515 participants, we found evidence of an association between percent emphysema and long-term pollution concentrations in an analysis leveraging between-city exposure contrasts. Higher concentrations of PM2.5 (5 μg/m3) and NOx (25 ppb) over the previous year were associated with 0.6 (95% CI: 0.1, 1.2%) and 0.5 (95% CI: 0.1, 0.9%) higher average percent emphysema, respectively. However, after adjustment for study site the associations were –0.6% (95% CI: –1.5, 0.3%) for PM2.5 and –0.5% (95% CI: –1.1, 0.02%) for NOx. Lower lung function measures (FEV1 and FVC) were associated with higher PM2.5 and NOx levels in 3,791 participants before and after adjustment for study site, though most associations were not statistically significant.
Conclusions: Associations between ambient air pollution and percentage of emphysema-like lung were inconclusive in this cross-sectional study, thus longitudinal analyses may better clarify these associations with percent emphysema.
Citation: Adar SD, Kaufman JD, Diez-Roux AV, Hoffman EA, D’Souza J, Stukovsky KH, Rich SS, Rotter JI, Guo X, Raffel LJ, Sampson PD, Oron AP, Raghunathan T, Barr RG. 2015. Air pollution and percent emphysema identified by computed tomography in the Multi-Ethnic Study of Atherosclerosis. Environ Health Perspect 123:144–151; http://dx.doi.org/10.1289/ehp.1307951
Ceramide causes endothelial apoptosis and emphysema-like changes in animal models.
Test if plasma sphingomyelin, a major precursor of ceramide, would predict longitudinal increase in the percentage of emphysema-like lung on computed tomography (CT).
Materials and methods
3,840 participants had their plasma sphingomyelin measured at baseline examination and their pulmonary emphysema measured on cardiac CT scans at baseline and on follow-up visits. Mixed effects models were used to adjust for potential confounders.
one standard deviation increase in sphingomyelin predicted a 0.12 % per year (95% CI: 0.02 to 0.22; p = 0.019) greater increase of percent emphysema.
Discussion and conclusion
Higher plasma levels of sphingomyelin predicted greater annual increase in quantitatively measured percent emphysema.
Sphingomyelin; Ceramide; Emphysema; Computed Tomography
To study the association between serum C-reactive protein (CRP) and urinary albumin excretion in the Multi-Ethnic Study of Atherosclerosis and to assess whether the association is modified by ethnicity, sex, or systolic blood pressure.
This was a cross-sectional study of 6675 participants who were free from macro albuminuria and clinical cardiovascular disease (mean age 62.1 years, 53% female; 39% White, 27% African American, 22% Hispanic, and 12% Chinese). Urinary albumin excretion was measured by spot urine albumin-to-creatinine ratio (ACR). Effect modifications were tested after adjusting for age, diabetes, body mass index, smoking, use of angiotensin-converting enzyme inhibitor or angiotensin-receptor blocker, other antihypertensive drugs, estrogens, statins, and high-density lipoprotein cholesterol and triglyceride levels.
The association between CRP and ACR was modified by ethnicity (P=.01) and sex (P<.001), but not by systolic blood pressure. After multivariate adjustment, the association remained in Chinese, African American, and Hispanic men and African American women (P<.02 for African American men, and P<.04 for the other subgroups).
The association between CRP and ACR was modified by ethnicity and sex; it was stronger in non-White men and African American women. These interactions have not been reported before, and future studies should consider them.
Albuminuria; C-Reactive Protein; Ethnicity; Gender
Cigarette smoking is the major cause of chronic obstructive pulmonary disease and emphysema. Recent studies suggest that susceptibility to cigarette smoke may vary by race/ethnicity; however, they were generally small and relied on self-reported race/ethnicity.
To test the hypothesis that relationships of smoking to lung function and percent emphysema differ by genetic ancestry and self-reported race/ethnicity among Whites, African-Americans, Hispanics and Chinese-Americans.
Cross-sectional population-based study of adults age 45-84 years in the United States
Principal components of genetic ancestry and continental ancestry estimated from one-million genome-wide single nucleotide polymorphisms. Pack-years calculated as years smoking cigarettes-per-day/20. Spirometry measured for 3,344 and percent emphysema on computed tomography for 8,224 participants.
The prevalence of ever-smoking was: Whites, 57.6%; African-Americans, 56.4%; Hispanics, 46.7%; and Chinese-Americans, 26.8%. Every 10 pack-years was associated with −0.73% (95% CI −0.90%, −0.56%) decrement in the forced expiratory volume in one second to forced vital capacity (FEV1/FVC) and a 0.23% (95% CI 0.08%, 0.38%) increase in percent emphysema. There was no evidence that relationships of pack-years to the FEV1/FVC, airflow obstruction and percent emphysema varied by genetic ancestry (all p>0.10), self-reported race/ethnicity (all p>0.10) or, among African-Americans, African ancestry. There were small differences in relationships of pack-years to the FEV1 among male Chinese-Americans and to the FEV1/FVC with African and Native American ancestry among male Hispanics only.
In this large cohort, there was little-to-no evidence that the associations of smoking to lung function and percent emphysema differed by genetic ancestry or self-reported race/ethnicity.
cigarette smoke; genetic ancestry; lung function; chronic obstructive pulmonary disease; COPD; emphysema; FVC; Forced Vital Capacity; FEV1; Forced Expiratory Volume in 1 second
Rationale: Basic research implicates alveolar endothelial cell apoptosis in the pathogenesis of chronic obstructive pulmonary disease (COPD) and emphysema. However, information on endothelial microparticles (EMPs) in mild COPD and emphysema is lacking.
Objectives: We hypothesized that levels of CD31+ EMPs phenotypic for endothelial cell apoptosis would be elevated in COPD and associated with percent emphysema on computed tomography (CT). Associations with pulmonary microvascular blood flow (PMBF), diffusing capacity, and hyperinflation were also examined.
Methods: The Multi-Ethnic Study of Atherosclerosis COPD Study recruited participants with COPD and control subjects age 50–79 years with greater than or equal to 10 pack-years without clinical cardiovascular disease. CD31+ EMPs were measured using flow cytometry in 180 participants who also underwent CTs and spirometry. CD62E+ EMPs phenotypic for endothelial cell activation were also measured. COPD was defined by standard criteria. Percent emphysema was defined as regions less than −950 Hounsfield units on full-lung scans. PMBF was assessed on gadolinium-enhanced magnetic resonance imaging. Hyperinflation was defined as residual volume/total lung capacity. Linear regression was used to adjust for potential confounding factors.
Measurements and Main Results: CD31+ EMPs were elevated in COPD compared with control subjects (P = 0.03) and were notably increased in mild COPD (P = 0.03). CD31+ EMPs were positively related to percent emphysema (P = 0.045) and were inversely associated with PMBF (P = 0.047) and diffusing capacity (P = 0.01). In contrast, CD62E+ EMPs were elevated in severe COPD (P = 0.003) and hyperinflation (P = 0.001).
Conclusions: CD31+ EMPs, suggestive of endothelial cell apoptosis, were elevated in mild COPD and emphysema. In contrast, CD62E+ EMPs indicative of endothelial activation were elevated in severe COPD and hyperinflation.
chronic obstructive pulmonary disease; emphysema; antigens, CD31; endothelium; pulmonary disease
Chronic obstructive pulmonary disease (COPD) is linked to cardiovascular disease; however, there are few studies on the associations of cardiovascular genes with COPD.
We assessed the association of lung function with 2,100 genes selected for cardiovascular diseases among 20,077 European-Americans and 6,900 African-Americans. We performed replication of significant loci in the other racial group and an independent consortium of Europeans, tested the associations of significant loci with percent emphysema, and examined gene expression in an independent sample. We then tested the association of a related lipid biomarker with FEV1/FVC and percent emphysema.
We identified one new polymorphism for FEV1/FVC (rs805301) in European-Americans (p=1.3×10−6) and a second (rs707974) in the combined European-American and African-American analysis (p=1.38×10−7). Both SNPs flank the gene for apolipoprotein M (apoM), a component of HDL. Both replicated in an independent cohort. SNPs in a second gene related to apoM and HDL, PCSK9, were associated with FEV1/FVC among African-Americans. rs707974 was associated with percent emphysema among European-Americans and African-Americans, and APOM expression was related to FEV1/FVC and percent emphysema. Higher HDL levels were associated with lower FEV1/FVC and greater percent emphysema.
These findings suggest a novel role for the APOM/HDL pathway in the pathogenesis of COPD and emphysema.
Apolipoproteins; Cholesterol; Percent Emphysema; Polymorphism, Single Nucleotide; Pulmonary Disease, Chronic Obstructive
Left ventricular (LV) mass is an important predictor of heart failure and cardiovascular mortality, yet determinants of LV mass are incompletely understood. Pulmonary hyperinflation in chronic obstructive pulmonary disease (COPD) may contribute to changes in intrathoracic pressure that increase LV wall stress. We therefore hypothesized that residual lung volume in COPD would be associated with greater LV mass.
Methods and results
The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study recruited smokers aged 50–79 years who were free of clinical cardiovascular disease. LV mass was measured by cardiac magnetic resonance. Pulmonary function testing was performed according to guidelines. Regression models were used to adjust for age, sex, body size, blood pressure and other cardiac risk factors.
Among 119 MESA COPD Study participants, mean age was 69±6 years, 55% were male and 65% had COPD, mostly of mild or moderate severity. Mean LV mass was 128±34 grams. Residual lung volume was independently associated with greater LV mass (7.2 grams per standard deviation increase in residual volume; 95% CI 2.2 to 12; P=0.004), and was similar in magnitude to that of systolic blood pressure (7.6 grams per standard deviation increase in systolic blood pressure, 95% CI 4.3 to 11 grams; p<0.001). Similar results were observed for LV mass to end-diastolic volume ratio (p=0.02) and with hyperinflation measured as residual volume to total lung capacity ratio (P=0.009).
Pulmonary hyperinflation, as measured by residual lung volume or residual lung volume to total lung capacity ratio, is associated with greater LV mass.
Left ventricular mass; hyperinflation; chronic obstructive pulmonary disease
Forced vital capacity (FVC), a spirometric measure of pulmonary function, reflects lung volume and is used to diagnose and monitor lung diseases. We performed genome-wide association study meta-analysis of FVC in 52,253 individuals from 26 studies and followed up the top associations in 32,917 additional individuals of European ancestry. We found six new regions associated at genome-wide significance (P < 5 × 10−8) with FVC in or near EFEMP1, BMP6, MIR-129-2/HSD17B12, PRDM11, WWOX, and KCNJ2. Two (GSTCD and PTCH1) loci previously associated with spirometric measures were related to FVC. Newly implicated regions were followed-up in samples of African American, Korean, Chinese, and Hispanic individuals. We detected transcripts for all six newly implicated genes in human lung tissue. The new loci may inform mechanisms involved in lung development and pathogenesis of restrictive lung disease.
Comorbidities are common in COPD, but quantifying their burden is difficult. Currently there is a COPD-specific comorbidity index to predict mortality and another to predict general quality of life. We sought to develop and validate a COPD-specific comorbidity score that reflects comorbidity burden on patient-centered outcomes.
Materials and Methods
Using the COPDGene study (GOLD II-IV COPD), we developed comorbidity scores to describe patient-centered outcomes employing three techniques: 1) simple count, 2) weighted score, and 3) weighted score based upon statistical selection procedure. We tested associations, area under the Curve (AUC) and calibration statistics to validate scores internally with outcomes of respiratory disease-specific quality of life (St. George's Respiratory Questionnaire, SGRQ), six minute walk distance (6MWD), modified Medical Research Council (mMRC) dyspnea score and exacerbation risk, ultimately choosing one score for external validation in SPIROMICS.
Associations between comorbidities and all outcomes were comparable across the three scores. All scores added predictive ability to models including age, gender, race, current smoking status, pack-years smoked and FEV1 (p<0.001 for all comparisons). Area under the curve (AUC) was similar between all three scores across outcomes: SGRQ (range 0·7624–0·7676), MMRC (0·7590–0·7644), 6MWD (0·7531–0·7560) and exacerbation risk (0·6831–0·6919). Because of similar performance, the comorbidity count was used for external validation. In the SPIROMICS cohort, the comorbidity count performed well to predict SGRQ (AUC 0·7891), MMRC (AUC 0·7611), 6MWD (AUC 0·7086), and exacerbation risk (AUC 0·7341).
Quantifying comorbidity provides a more thorough understanding of the risk for patient-centered outcomes in COPD. A comorbidity count performs well to quantify comorbidity in a diverse population with COPD.
DNA methylation is one of several epigenetic mechanisms that contribute to the regulation of gene expression; however, the extent to which methylation of CpG dinucleotides correlates with gene expression at the genome-wide level is still largely unknown. Using purified primary monocytes from subjects in a large community-based cohort (n = 1264), we characterized methylation (>485 000 CpG sites) and mRNA expression (>48K transcripts) and carried out genome-wide association analyses of 8370 expression phenotypes. We identified 11 203 potential cis-acting CpG loci whose degree of methylation was associated with gene expression (eMS) at a false discovery rate threshold of 0.001. Most of the associations were consistent in effect size and direction of effect across sex and three ethnicities. Contrary to expectation, these eMS were not predominately enriched in promoter regions, or CpG islands, but rather in the 3′ UTR, gene bodies, CpG shores or ‘offshore’ sites, and both positive and negative correlations between methylation and expression were observed across all locations. eMS were enriched for regions predicted to be regulatory by ENCODE (Encyclopedia of DNA Elements) data in multiple cell types, particularly enhancers. One of the strongest association signals detected (P < 2.2 × 10−308) was a methylation probe (cg17005068) in the promoter/enhancer region of the glutathione S-transferase theta 1 gene (GSTT1, encoding the detoxification enzyme) with GSTT1 mRNA expression. Our study provides a detailed description of the epigenetic architecture in human monocytes and its relationship to gene expression. These data may help prioritize interrogation of biologically relevant methylation loci and provide new insights into the epigenetic basis of human health and diseases.
The potential consequences of asthma in childhood and young adulthood on lung structure in older adults have not been studied in a large, population-based cohort.
The authors hypothesized that a history of asthma onset in childhood (age 18 or before) or young adulthood (age 19 to 45) was associated with altered lung structure on computed tomography (CT) in later life.
The Multi-Ethnic Study of Atherosclerosis Lung Study recruited 3,965 participants and assessed asthma history using standardized questionnaires, spirometry following guidelines, and segmental airway dimensions and percent low attenuation areas on CT scans.
Asthma with onset in childhood and young adulthood was associated with large decrements in the forced expiratory volume in one second among participants with a mean age of 66 years (−365 ml and −343 ml, respectively; P<0.001). Asthma with onset in childhood and young adulthood was associated with increased mean airway wall thickness standardized to an internal perimeter of 10 mm (Pi10) (0.1 mm, P<0.001 for both), predominantly from narrower segmental airway lumens (−0.39 mm and −0.34 mm, respectively; P<0.001). Asthma with onset in childhood and young adulthood also was associated with a greater percentage of low attenuation areas (1.69% and 4.30%, respectively; P<0.001). Findings were similar among never smokers except that differential percentage of low attenuation areas in child-onset asthma was not seen in them.
Asthma with onset in childhood or young adulthood, was associated with reduced lung function, narrower airways and, among asthmatics who smoked, greater percentage of low attenuation areas in later life.
airway remodeling; airway structure; asthma; emphysema; epidemiology
Asthma and chronic obstructive pulmonary disease (COPD) are thought to share a genetic background (“Dutch hypothesis”).
We investigated whether asthma and COPD have common underlying genetic factors, performing genome-wide association studies for both asthma and COPD and combining the results in meta-analyses.
Three loci showed potential involvement in both diseases: chr2p24.3, chr5q23.1 and chr13q14.2, containing DDX1, COMMD10 (both participating in the NFκβ pathway) and GNG5P5, respectively. SNP rs9534578 in GNG5P5 reached genome-wide significance after first stage replication (p=9.96·*10−9). The second stage replication in seven independent cohorts provided no significant replication. eQTL analysis in blood and lung on the top 20 associated SNPs identified two SNPs in COMMD10 influencing gene expression.
Inflammatory processes differ in asthma and COPD and are mediated by NFκβ, which could be driven by the same underlying genes, COMMD10 and DDX1. None of the SNPs reached genome-wide significance. Our eQTL studies support a functional role of two COMMD10 SNPs, since they influence gene expression in both blood cells and lung tissue. Our findings either suggest that there is no common genetic component in asthma and COPD or, alternatively, different environmental factors, like lifestyle and occupation in different countries and continents may have obscured the genetic common contribution.
COPD is characterized by reduced airway lumen dimensions and fewer peripheral airways. Most studies of airway properties sample airways based upon lumen dimension or at random, which may bias comparisons given reduced airway lumen dimensions and number in COPD. We sought to compare central airway wall dimensions on computed tomography (CT) in COPD and controls using spatially matched airways, thereby avoiding selection bias of airways in the lung.
The MESA COPD Study and SPIROMICS recruited smokers with COPD and controls aged 50–79 years and 40–80 years, respectively. COPD was defined by current guidelines. Using CT image data, airway dimensions were measured for all central airway segments (generations 0–6) following 5 standardized paths into the lungs. Case-control airway comparisons were spatially matched by generation and adjusted for demographics, body size, smoking, CT dose, percent emphysema, airway length, and lung volume.
Among 311 MESA COPD participants, airway wall areas at generations 3–6 were smaller in COPD compared to controls(all p<0.001). Among 1248 SPIROMICS participants, airway wall areas at generations 1–6 were smaller(all p<0.001), and this reduction was monotonic with increasing COPD severity(P<0.001). In both studies, sampling airways by lumen diameter or randomly resulted in a comparison of more proximal airways in COPD to more peripheral airways in controls(p<0.001) resulting in the appearance of thicker walls in COPD(p<0.02).
Airway walls are thinner in COPD when comparing spatially matched central airways. Other approaches to airway sampling result in comparisons of more proximal to more distal airways and potentially biased assessment of airway properties in COPD.
Chronic obstructive pulmonary disease; computed tomography; airways; walls
Reduced forced expiratory volume in 1 second (FEV1) and the ratio of FEV1 to forced vital capacity (FVC) are strong predictors of mortality and lung function is higher among individuals with exceptional longevity. However, genetic factors associated with lung function in individuals with exceptional longevity have not been identified.
We conducted a genome wide association study (GWAS) to identify novel genetic variants associated with lung function in the Long Life Family Study (LLFS) (n = 3,899). Replication was performed using data from the CHARGE/SpiroMeta consortia. The association between SNPs and FEV1 and FEV1/FVC was analyzed using a linear mixed effects model adjusted for age, age2, sex, height, field center, ancestry principal components and kinship structure to adjust for family relationships separately for ever smokers and never smokers. In the linkage analysis, we used the residuals of the FEV1 and FEV1/FVC, adjusted for age, sex, height, ancestry principal components (PCs), smoking status, pack-years, and field center.
We identified nine SNPs in strong linkage disequilibrium in the CYP2U1 gene to be associated with FEV1 and a novel SNP (rs889574) associated with FEV1/FVC, none of which were replicated in the CHARGE/SpiroMeta consortia. Using linkage analysis, we identified a novel linkage peak in chromosome 2 at 219 cM for FEV1/FVC (LOD: 3.29) and confirmed a previously reported linkage peak in chromosome 6 at 28 cM (LOD: 3.33) for FEV1.
Future studies need to identify the rare genetic variants underlying the linkage peak in chromosome 6 for FEV1.
Electronic supplementary material
The online version of this article (doi:10.1186/s12931-014-0134-x) contains supplementary material, which is available to authorized users.
GWAS; Lung function; Aging
Chronic obstructive pulmonary disease (COPD) has been classically divided into blue bloaters and pink puffers. The utility of these clinical subtypes is unclear. However, the broader distinction between airway-predominant and emphysema-predominant COPD may be clinically relevant. The objective was to define clinical features of emphysema-predominant and non-emphysematous COPD patients.
Current and former smokers from the Genetic Epidemiology of COPD Study (COPDGene) had chest computed tomography (CT) scans with quantitative image analysis. Emphysema-predominant COPD was defined by low attenuation area at -950 Hounsfield Units (LAA-950) ≥10%. Non-emphysematous COPD was defined by airflow obstruction with minimal to no emphysema (LAA-950 < 5%).
Out of 4197 COPD subjects, 1687 were classified as emphysema-predominant and 1817 as non-emphysematous; 693 had LAA-950 between 5–10% and were not categorized. Subjects with emphysema-predominant COPD were older (65.6 vs 60.6 years, p < 0.0001) with more severe COPD based on airflow obstruction (FEV1 44.5 vs 68.4%, p < 0.0001), greater exercise limitation (6-minute walk distance 1138 vs 1331 ft, p < 0.0001) and reduced quality of life (St. George’s Respiratory Questionnaire score 43 vs 31, p < 0.0001). Self-reported diabetes was more frequent in non-emphysematous COPD (OR 2.13, p < 0.001), which was also confirmed using a strict definition of diabetes based on medication use. The association between diabetes and non-emphysematous COPD was replicated in the ECLIPSE study.
Non-emphysematous COPD, defined by airflow obstruction with a paucity of emphysema on chest CT scan, is associated with an increased risk of diabetes. COPD patients without emphysema may warrant closer monitoring for diabetes, hypertension, and hyperlipidemia and vice versa.
Clinicaltrials.gov identifiers: COPDGene NCT00608764, ECLIPSE NCT00292552.
Electronic supplementary material
The online version of this article (doi:10.1186/1471-2466-14-164) contains supplementary material, which is available to authorized users.
Airway disease; CT scan; Diabetes mellitus; Emphysema; Spirometry
Autopsy studies show that smoking contributes to airway wall hyperplasia and narrowing of the airway lumen. Studies of smoking and airway measures on computed tomography (CT) scan are limited to case-control studies of measures that combine airway lumen and wall thickness.
We hypothesized that cumulative cigarette smoking would be associated with increased airway wall thickness in a large, population-based cohort.
The Multi-Ethnic Study of Atherosclerosis enrolled participants age 45-84 years from the general population. Smoking history was assessed via standardized questionnaire items; current smoking was confirmed in half the cohort with cotinine. Airway lumen and wall thickness were measured in two dimensions in posterior basal segmental bronchi on cardiac-gated CT scans. Analyses were adjusted for age, gender, genetic ancestry, education, height, weight, asthma history, particulate matter, scanner type, and scanner current.
Half of the 7,898 participants had smoked and 14% were current smokers. Pack-years of smoking were associated with thicker airway walls (mean increase 0.002 mm per ten pack-years [95% CI: 0.00002, 0.004] p=0.03). Current smoking was associated with narrower airway lumens (mean decrease −0.11 mm [95% CI: −0.2, −0.02] p=0.02). There was no evidence that either association was modified by genetic ancestry, and findings persisted among participants without clinical disease.
Long-term cigarette smoking was associated with subclinical increases in wall thickness of sub-segmental airways whereas current smoking was associated with narrower airway lumen diameters. Smoking may contribute to airway wall thickening prior to the development of overt chronic obstructive pulmonary disease.
smoking; airway remodeling; Pi10; wall thickness; lumen; chronic obstructive pulmonary disease
Inflammation contributes to the pathogenesis of disease associated with the left ventricle (LV); yet, our understanding of the effect of inflammation on the right ventricle (RV) is quite limited.
Methods and results
The relationships of C-reactive protein (CRP), interleukin-6 (IL-6) and fibrinogen with RV morphology and function (from cardiac MRI) were examined in participants free of clinical cardiovascular disease (n=4,009) from the Multi-Ethnic Study of Atherosclerosis (MESA)-RV study. Multivariable regressions (linear, quantile [25th and 75th] and generalized additive models [GAM]) were used to examine the independent association of CRP, IL-6 and fibrinogen with RV mass, RV end-diastolic volume (RVEDV), RV end-systolic volume (RVESV), RV stroke volume (RVSV) and RV ejection fraction (RVEF). Unadjusted and adjusted analyses revealed strong inverse associations between both CRP and IL-6 with RV mass, RVEDV, RVESV and RVSV (all p<0.01); there were no associations with RVEF. These relationships remained significant after adjustment for the respective LV parameters and lung function. However, GAM models suggested that extreme values of CRP and IL-6 might have positive associations with RV parameters. Fibrinogen showed significant associations in unadjusted models, but no associations after adjustment or in sensitivity analyses.
Levels of CRP and IL-6 are independently associated with RV morphology even after adjustment for the respective LV measure in this multi-ethnic population free of cardiovascular disease. Systemic inflammation may contribute to RV structural changes independent of effects on the LV.
Systemic inflammation; right ventricle; heart failure; Multi-Ethnic Study of Atherosclerosis
Data on the relations of different types of fish meals and long-chain n-3 polyunsaturated fatty acids (n-3 PUFAs) with measures of atherosclerosis are sparse.
We examined intakes of long-chain n-3 PUFAs and fish in relation to clinical measures of subclinical atherosclerosis.
A cross-sectional study was conducted in 5,488 multiethnic adults aged 45–84 years and free of clinical cardiovascular disease. Diet was assessed using self-administered food frequency questionnaires. Subclinical atherosclerosis was determined by common carotid intima-media thickness (cCIMT, >80th percentile), internal CIMT (iCIMT, >80th percentile), coronary artery calcium score (CAC, >0) or ankle-brachial index (ABI, <0.90), respectively.
After adjustment for potential confounders, intakes of long-chain n-3 PUFAs and non-fried (broiled, steamed, baked or raw) fish were inversely related to subclinical atherosclerosis determined by cCIMT but not iCIMT, CAC or ABI. The multivariable odds ratio comparing the highest to the lowest quartile of dietary exposures in relation to subclinical atherosclerosis determined by cCIMT was 0.69 (95% CI: 0.55, 0.86; p for trend<0.01) for n-3 PUFA intake, 0.80 (95% CI: 0.64, 1.01; p=0.054) for non-fried fish and 0.90 (95% CI: 0.73, 1.10; p=0.33) for fried fish consumption.
This study indicates that dietary intake of long-chain n-3 PUFAs or non-fried fish is associated with lower prevalence of subclinical atherosclerosis classified by cCIMT although significant changes in iCIMT, CAC and ABI were not observed. Our findings also suggest that the association of fish and atherosclerosis may vary depending on the type of fish meal consumed and the measures of atherosclerosis.
long-chain n-3 polyunsaturated fatty acids; fish; fish oil; biomarker; subclinical atherosclerosis; multi-ethnicities
Rationale: Relationships between chronic health conditions and acute infections remain poorly understood. Preclinical studies suggest crosstalk between nervous and immune systems.
Objectives: To determine bidirectional relationships between cognition and pneumonia.
Methods: We conducted longitudinal analyses of a population-based cohort over 10 years. We determined whether changes in cognition increase risk of pneumonia hospitalization by trajectory analyses and joint modeling. We then determined whether pneumonia hospitalization increased risk of subsequent dementia using a Cox model with pneumonia as a time-varying covariate.
Measurements and Main Results: Of the 5,888 participants, 639 (10.9%) were hospitalized with pneumonia at least once. Most participants had normal cognition before pneumonia. Three cognition trajectories were identified: no, minimal, and severe rapid decline. A greater proportion of participants hospitalized with pneumonia were on trajectories of minimal or severe decline before occurrence of pneumonia compared with those never hospitalized with pneumonia (proportion with no, minimal, and severe decline were 67.1%, 22.8%, and 10.0% vs. 76.0%, 19.3%, and 4.6% for participants with and without pneumonia, respectively; P < 0.001). Small subclinical changes in cognition increased risk of pneumonia, even in those with normal cognition and physical function before pneumonia (β = −0.02; P < 0.001). Participants with pneumonia were subsequently at an increased risk of dementia (hazard ratio, 2.24 [95% confidence interval, 1.62–3.11]; P = 0.01). Associations were independent of demographics, health behaviors, other chronic conditions, and physical function. Bidirectional relationship did not vary based on severity of disease, and similar associations were noted for those with severe sepsis and other infections.
Conclusions: A bidirectional relationship exists between pneumonia and cognition and may explain how a single episode of infection in well-appearing older individuals accelerates decline in chronic health conditions and loss of functional independence.
pneumonia; dementia; cognitive function
Asthma originates from genetic and environmental factors with about half the risk of disease attributable to heritable causes. Genome-wide association studies, mostly in populations of European ancestry, have identified numerous asthma-associated single nucleotide polymorphisms (SNPs). Studies in populations with diverse ancestries allow both for identification of robust associations that replicate across ethnic groups and for improved resolution of associated loci due to different patterns of linkage disequilibrium between ethnic groups. Here we report on an analysis of 745 African-American subjects with asthma and 3,238 African-American control subjects from the Candidate Gene Association Resource (CARe) Consortium, including analysis of SNPs imputed using 1,000 Genomes reference panels and adjustment for local ancestry. We show strong evidence that variation near RAD50/IL13, implicated in studies of European ancestry individuals, replicates in individuals largely of African ancestry. Fine mapping in African ancestry populations also refined the variants of interest for this association. We also provide strong or nominal evidence of replication at loci near ORMDL3/GSDMB, IL1RLML18R1, and 10pl4, all previously associated with asthma in European or Japanese populations, but not at the PYHIN1 locus previously reported in studies of African-American samples. These results improve the understanding of asthma genetics and further demonstrate the utility of genetic studies in populations other than those of largely European ancestry.
epidemiology; survey; urban health