Pulmonary Disease and Age at Immigration among Hispanics. Results from the Hispanic Community Health Study/Study of Latinos

Association of Serum Lipids and Obstructive Lung Disease in Hispanic/Latino Adults of Diverse Backgrounds

Rationale

Substantial variation in the prevalences of obstructive lung disease exist between Hispanic/Latino heritage groups. Experimental studies have posited biological mechanisms linking serum lipids and lipid-lowering medications with obstructive lung disease. The aim of this study is to examine the associations of serum lipid levels with the prevalences of asthma and chronic obstructive pulmonary disease in the Hispanic Community Health Study/Study of Latinos and how these associations vary by Hispanic/Latino heritage group.

Methods

The Hispanic Community Health Study/Study of Latinos is a population-based probability sample of 16,415 self-identified Hispanic/Latino persons aged 18–74 years recruited between 2008 and 2011 from randomly selected households in four US field centers. The baseline clinical examination included comprehensive biological testing (fasting serum lipid levels), behavioral and socio-demographic assessments, medication inventory including inhalers, and respiratory data including questionnaires for asthma and standardized spirometry with post-bronchodilator measures for identification of obstructive lung disease.

Measurements and main results

Hispanic/Latinos with current asthma had lower age- and statin-use-adjusted mean serum total cholesterol, low-density lipoprotein cholesterol, and triglyceride levels than their non-asthmatic counterparts. In analysis adjusted for age plus gender, ethnicity, cigarette smoking, alcohol intake, body mass index, lipid/cholesterol-lowering medications, age at immigration, health insurance status, and use of oral corticosteroids, increasing serum levels of total cholesterol and low-density lipoprotein cholesterol were associated with lower odds of current asthma in the estimated population. Unlike asthma, Hispanic/Latinos with chronic obstructive pulmonary disease had lower mean high-density lipoprotein than their non- chronic obstructive pulmonary disease counterparts. In the fully adjusted analysis no significant associations were found between lipid levels and prevalent chronic obstructive pulmonary disease.

Conclusions

We showed a modest inverse relationship between serum lipid levels and current asthma. These results highlight some important differences in Hispanics/Latinos and certain serum lipids may be factors or markers of obstructive lung disease.

What Ancestry Can Tell Us About the Genetic Origins of Inter-Ethnic Differences in Asthma Expression

Differences in asthma prevalence have been described across different populations, suggesting that genetic ancestry can play an important role in this disease. In fact, several studies have demonstrated an association between African ancestry with increased asthma susceptibility and severity, higher immunoglobulin E levels, and lower lung function. In contrast, Native American ancestry has been shown to have a protective role for this disease. Genome-wide association studies have allowed the identification of population-specific genetic variants with varying allele frequency among populations. Additionally, the correlation of genetic ancestry at the chromosomal level with asthma and related traits by means of admixture mapping has revealed regions of the genome where ancestry is correlated with the disease. In this review, we discuss the evidence supporting the association of genetic ancestry with asthma susceptibility and asthma-related traits, and highlight the regions of the genome harboring ancestry-specific genetic risk factors.

Smoking intensity and duration is associated with cardiac structure and function: the ECHOcardiographic Study of Hispanics/Latinos

Objective

Cardiovascular disease is the leading cause of death in smokers and this relationship is complicated by the multiplicity of cardiovascular effects of smoking. However, the relationship between intensity and duration of cigarette smoking and echocardiographic measures of right and left ventricular structure and function has been poorly studied.

Methods

We examined ECHO-SOL (Echocardiographic Study of Hispanics/Latinos) participants, a subset of the Hispanic Community Health Study/Study of Latinos. Participants were administered a detailed tobacco exposure questionnaire and a comprehensive echocardiography exam. Multivariable linear regression models (adjusted for age, sex, obesity, hypertension and diabetes statuses) were performed using sampling weights. Statistical significance was defined at p<0.01.

Results

There were 1818 ECHO-SOL participants (57.4% women, mean age 56.4 years). Among current smokers (n=304), increased duration of smoking, as measured by a younger age of smoking initiation, was significantly associated with higher mean left ventricular mass (LVM) and lower right ventricular (RV) function (lower right ventricular stroke volumes). More cigarettes smoked per day was significantly associated with higher mean LVM, worse diastolic function (higher E/e′ ratio), worse LV geometry (increased relative wall thickness) and worse RV function (decreasing right ventricular stroke volume). Among current smokers, higher mean lifetime pack-years (a combined measure of smoking intensity and duration) was associated with higher LVM, worse LV geometry, worse diastolic function, greater RV dilatation and worse RV function.

Conclusions

There is a dose–response relationship between intensity and duration of cigarette tobacco smoking with unfavourable changes of multiple measures of right-sided and left-sided cardiac structure and function.

Effect of Relocation to the U.S. on Asthma Risk Among Hispanics

INTRODUCTION

Asthma prevalence is reportedly higher among U.S.-born relative to foreign-born Hispanics/Latinos. Little is known about rates of asthma onset before and after relocation to the U.S. in Latinos. Asthma rates were examined by U.S. residence and country/territory of origin.

METHODS

In 2015-2016, age at first onset of asthma symptoms was analyzed, defined retrospectively from a cross-sectional survey in 2008-2011, in relation to birthplace and U.S. residence among 15,573 U.S.-dwelling participants (aged 18-76 years) in the Hispanic Community Health Study/Study of Latinos.

RESULTS

Cumulative incidence of asthma through age 30 years ranged from 7.9% among Mexican background individuals to 29.4% among those of Puerto Rican background. Among those born outside the U.S. mainland, the adjusted hazard for asthma was 1.52-fold higher (95% CI=1.25, 1.85) after relocation versus before relocation to the U.S. mainland, with heterogeneity in this association by Hispanic/Latino background (p-interaction<0.0001). Among foreign-born Dominicans and Mexicans, rates of asthma were greater after relocation versus before relocation (adjusted hazard ratio [AHR] for after versus before relocation, 2.42, 95% CI=1.44, 4.05 among Dominicans; AHR=2.90, 95% CI=2.02, 4.16 among Mexicans). Puerto Ricans had modestly increased asthma onset associated with U.S. mainland residence (AHR=1.52, 95% CI=1.06, 2.17). No similar increase associated with U.S. residence was observed among Central/South American immigrants (AHR=0.94, 95% CI=0.53, 1.67). Asthma rates among Cuban immigrants were lower after relocation (AHR=0.45, 95% CI=0.24, 0.82).

CONCLUSIONS

The effect of relocation to the U.S. on asthma risk among Hispanics is not uniform across Hispanic/Latino groups.

How Well Does CAPTURE Translate?: An Exploratory Analysis of a COPD Case-Finding Method for Spanish-Speaking Patients

BACKGROUND

This study tested the properties of a Spanish translation of CAPTURE (COPD Assessment in Primary Care To Identify Undiagnosed Respiratory Disease and Exacerbation Risk) with selective use of peak expiratory flow (PEF).

METHODS

This study comprised analyses of data from the Spanish-speaking cohort of the cross-sectional, case-control study used to develop CAPTURE. Translation procedures included forward and backward translation, reconciliation, and cognitive interviewing to assure linguistic and cultural equivalence, yielding CAPTURE-S. Spanish-speaking participants were recruited through one center and designated as case subjects (clinically significant COPD: FEV₁ ≤ 60% predicted and/or at risk of COPD exacerbation) or control subjects (no or mild COPD). Subjects completed a questionnaire booklet that included 44 candidate items, the COPD Assessment Test (CAT), and the modified Medical Research Council (mMRC) dyspnea question. PEF and spirometry were also performed.

RESULTS

The study included 30 participants (17 case subjects and 13 control subjects). Their mean (± SD) age was 62.6 (11.49) years, and 33% were male. CAPTURE-S scores were significantly correlated with PEF (r = -0.78), the FEV₁/FVC ratio (r = -0.74), FEV₁ (r = -0.69), FEV₁ % predicted (r = -0.69), the CAT score (r = 0.70), and the mMRC dyspnea question (r = 0.59) (P < .0001), with significantly higher scores in case subjects than in control subjects (t = 6.16; P < .0001). PEF significantly correlated with FEV₁ (r = 0.89), FEV₁ % predicted (r = 0.79), and the FEV₁/FVC ratio (r = 0.75) (P < .0001), with significantly lower PEF in case subjects than in control subjects (t = 5.08; P < .0001). CAPTURE-S score + PEF differentiated case subjects and control subjects with a sensitivity of 88.2% and a specificity of 92.3%.

CONCLUSIONS

CAPTURE-S with selective use of PEF seems to be useful for identifying Spanish-speaking patients in need of diagnostic evaluation for clinically significant COPD who may benefit from initiation of COPD treatment.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01880177; URL: www.clinicaltrials.gov.

Association of systemic inflammation, adiposity, and metabolic dysregulation with asthma burden among Hispanic adults

RATIONALE

Obesity-related asthma is associated with higher disease burden than normal-weight asthma among Hispanics. Adiposity, metabolic dysregulation, and inflammation are all implicated in pathogenesis of obesity-related asthma, but their independent contributions are poorly understood.

OBJECTIVE

To examine the independent contributions of body fat distribution, metabolic abnormalities and inflammation on asthma symptoms and pulmonary function among Hispanics.

METHODS

Participants of the Hispanic Community Health Study/Study of Latinos with doctor-diagnosed asthma who completed an asthma symptom questionnaire and performed a valid spirometry were included in the analysis (n = 1126). Multivariate analysis was used to examine the independent association of general adiposity (assessed using body mass index), truncal adiposity (assessed by waist circumference), metabolic dysregulation (presence of insulin resistance and low HDL) and inflammation (high-sensitivity C-Reactive Protein≥3 mg/L) with reported asthma symptoms or pulmonary function measures (FEV₁, and FVC) while adjusting for demographic and clinical covariates.

RESULTS

Of the 1126 participants, 334 (29.5%) were overweight, and 648 (57.8%) were obese. FEV₁ and FVC were lower in obese compared to normal-weight asthmatics. In analyses controlling for metabolic and adiposity factors, high hs-CRP (>7 mg/L) was associated with more symptoms (prevalence-ratio 1.27 (95%CI 1.05, 1.54), and lower FVC (β -138 ml (95%CI -27 ml, -249 ml)) and FEV₁ (β -155 ml (95% CI -38 ml, -272 ml). Low HDL was also associated with lower FVC (β -111 ml (-22 ml, -201 ml) and FEV₁ (β -100 ml (-12 ml, -188 ml)). Results were similar in men and women.

CONCLUSIONS

Our findings suggest that hs-CRP and low HDL, rather than general and truncal adiposity, are associated with asthma burden among overweight and obese Hispanic adults.

Respiratory Health in Migrant Populations: A Crisis Overlooked

The crisis in the Middle East has raised awareness about the challenges encountered by migrant populations, in particular, health-care access and delivery. Similar challenges are encountered by migrant populations around the world, including those entering the United States as refugees and/or survivors of torture as well as Mexicans and other Latin Americans crossing the border. During the 2016 International American Thoracic Society Meeting held in San Francisco, California, a group of researchers and health-care providers discussed these challenges at a minisymposium devoted to the respiratory health of migrants. The discussion focused on the increased incidence of airway diseases among individuals migrating to more developed countries, the problems created by sleep disorders and their implications for cardiovascular and mental health, the challenges inherent in the control of infections in refugee populations, and the problems resulting from deportation. The group also discussed the potential impact of novel strategies made available by Internet-based technologies and how these strategies could be deployed to support worldwide efforts in assisting migrants and refugees, even in countries that find themselves in the direst circumstances. These presentations are summarized in this document, which is not meant to be exhaustive, but to improve awareness about the challenges confronted by migrants and their host nations regarding respiratory health-care access and delivery, and about the need for adequate investment of resources to better define these challenges through research and for the development of efficient strategies for intervention.

Differential methylation between ethnic sub-groups reflects the effect of genetic ancestry and environmental exposures

Populations are often divided categorically into distinct racial/ethnic groups based on social rather than biological constructs. Genetic ancestry has been suggested as an alternative to this categorization. Herein, we typed over 450,000 CpG sites in whole blood of 573 individuals of diverse Hispanic origin who also had high-density genotype data. We found that both self-identified ethnicity and genetically determined ancestry were each significantly associated with methylation levels at 916 and 194 CpGs, respectively, and that shared genomic ancestry accounted for a median of 75.7% (IQR 45.8% to 92%) of the variance in methylation associated with ethnicity. There was a significant enrichment (p=4.2×10-64) of ethnicity-associated sites amongst loci previously associated environmental exposures, particularly maternal smoking during pregnancy. We conclude that differential methylation between ethnic groups is partially explained by the shared genetic ancestry but that environmental factors not captured by ancestry significantly contribute to variation in methylation.

Prevalence of Asthma in School Children on the Arizona-Sonora Border

BACKGROUND

Mexican-born children living in the United States have a lower prevalence of asthma than other US children. Although children of Mexican descent near the Arizona (AZ)-Sonora border are genetically similar, differences in environmental exposures might result in differences in asthma prevalence across this region.

OBJECTIVE

The objective of this study was to determine if the prevalence of asthma and wheeze in these children varies across the AZ-Sonora border.

METHODS

The International Study of Asthma and Allergy in Children written and video questionnaires were administered to 1753 adolescents from 5 middle schools: Tucson (school A), Nogales, AZ (schools B, C), and Nogales, Sonora, Mexico (schools D, E). The prevalence of asthma and symptoms was compared, with analyses in the AZ schools limited to self-identified Mexican American students.

RESULTS

Compared with the Sonoran reference school E, the adjusted odds ratio (OR) for asthma was significantly higher in US schools A (OR 4.89, 95% confidence interval [CI] 2.72-8.80), B (OR 3.47, 95% CI 1.88-6.42), and C (OR 4.12, 95% CI 1.78-9.60). The adjusted OR for wheeze in the past year was significantly higher in schools A (OR 2.19, 95% CI 1.20-4.01) and B (OR 2.67, 95% CI 1.42-5.01) on the written questionnaire and significantly higher in A (OR 2.13, 95% CI 1.22-3.75), B (OR 1.95, 95% CI 1.07-3.53), and Sonoran school D (OR 2.34, 95% CI 1.28-4.30) on the video questionnaire compared with school E.

CONCLUSIONS

Asthma and wheeze prevalence differed significantly between schools and was higher in the United States. Environmental factors that may account for these differences could provide insight into mechanisms of protection from asthma.

Towards Equity in Health: Researchers Take Stock

For the 2016 end-of-the-year editorial, the PLOS Medicine editors asked 7 global health leaders to discuss developments relevant to the equitable provision of medical care to all populations. The result is a collection of expert views on ethical trial design, research during outbreaks, high-burden infectious diseases, diversity in research and protection of migrants.

Control for Population Structure and Relatedness for Binary Traits in Genetic Association Studies via Logistic Mixed Models

Linear mixed models (LMMs) are widely used in genome-wide association studies (GWASs) to account for population structure and relatedness, for both continuous and binary traits. Motivated by the failure of LMMs to control type I errors in a GWAS of asthma, a binary trait, we show that LMMs are generally inappropriate for analyzing binary traits when population stratification leads to violation of the LMM's constant-residual variance assumption. To overcome this problem, we develop a computationally efficient logistic mixed model approach for genome-wide analysis of binary traits, the generalized linear mixed model association test (GMMAT). This approach fits a logistic mixed model once per GWAS and performs score tests under the null hypothesis of no association between a binary trait and individual genetic variants. We show in simulation studies and real data analysis that GMMAT effectively controls for population structure and relatedness when analyzing binary traits in a wide variety of study designs.

Pulmonary Disease and Age at Immigration among Hispanics. Results from the Hispanic Community Health Study/Study of Latinos

RATIONALE

Asthma has been reported to be more prevalent among Hispanics of Puerto Rican heritage than among other Hispanics and among Hispanics born in the United States or who immigrated as children than among those who came as adults; however, direct comparisons across Hispanic groups are lacking.

OBJECTIVES

To test whether asthma is more prevalent among Hispanics of Puerto Rican heritage than among other Hispanic groups, whether asthma is associated with age of immigration, and whether chronic obstructive pulmonary disease varies by heritage in a large, population-based cohort of Hispanics in the United States.

METHODS

The Hispanic Community Health Study/Study of Latinos researchers recruited a population-based probability sample of 16,415 Hispanics/Latinos, 18-74 years of age, in New York City, Chicago, Miami, and San Diego. Participants self-reported Puerto Rican, Cuban, Dominican, Mexican, Central American, or South American heritage; birthplace; and, if relevant, age at immigration. A respiratory questionnaire and standardized spirometry were performed with post-bronchodilator measures for those with airflow limitation.

MEASUREMENTS AND MAIN RESULTS

The prevalence of physician-diagnosed asthma among Puerto Ricans (36.5%; 95% confidence interval, 33.6-39.5%) was higher than among other Hispanics (odds ratio, 3.9; 95% confidence interval, 3.3-4.6). Hispanics who were born in the mainland United States or had immigrated as children had a higher asthma prevalence than those who had immigrated as adults (19.6, 19.4, and 14.1%, respectively; P < 0.001). Current asthma, bronchodilator responsiveness, and wheeze followed similar patterns. Chronic obstructive pulmonary disease prevalence was higher among Puerto Ricans (14.1%) and Cubans (9.8%) than among other Hispanics (<6.0%), but it did not vary across Hispanic heritages after adjustment for smoking and prior asthma (P = 0.22), by country of birth, or by age at immigration.

CONCLUSIONS

Asthma was more prevalent among Puerto Ricans, other Hispanics born in the United States, and those who had immigrated as children than among other Hispanics. In contrast, the higher prevalence of chronic obstructive pulmonary disease among Puerto Ricans and Cubans was largely reflective of differential smoking patterns and asthma.

Genetic Diversity and Association Studies in US Hispanic/Latino Populations: Applications in the Hispanic Community Health Study/Study of Latinos

US Hispanic/Latino individuals are diverse in genetic ancestry, culture, and environmental exposures. Here, we characterized and controlled for this diversity in genome-wide association studies (GWASs) for the Hispanic Community Health Study/Study of Latinos (HCHS/SOL). We simultaneously estimated population-structure principal components (PCs) robust to familial relatedness and pairwise kinship coefficients (KCs) robust to population structure, admixture, and Hardy-Weinberg departures. The PCs revealed substantial genetic differentiation within and among six self-identified background groups (Cuban, Dominican, Puerto Rican, Mexican, and Central and South American). To control for variation among groups, we developed a multi-dimensional clustering method to define a "genetic-analysis group" variable that retains many properties of self-identified background while achieving substantially greater genetic homogeneity within groups and including participants with non-specific self-identification. In GWASs of 22 biomedical traits, we used a linear mixed model (LMM) including pairwise empirical KCs to account for familial relatedness, PCs for ancestry, and genetic-analysis groups for additional group-associated effects. Including the genetic-analysis group as a covariate accounted for significant trait variation in 8 of 22 traits, even after we fit 20 PCs. Additionally, genetic-analysis groups had significant heterogeneity of residual variance for 20 of 22 traits, and modeling this heteroscedasticity within the LMM reduced genomic inflation for 19 traits. Furthermore, fitting an LMM that utilized a genetic-analysis group rather than a self-identified background group achieved higher power to detect previously reported associations. We expect that the methods applied here will be useful in other studies with multiple ethnic groups, admixture, and relatedness.