Difference in airflow obstruction between Hispanic and non-Hispanic White female smokers

Racial and Ethnic Minorities Have a Lower Prevalence of Airflow Obstruction than Non-Hispanic Whites

Racial and ethnic disparities in chronic obstructive pulmonary disease (COPD) are not well-studied. Our objective was to examine differences in limited COPD-related outcomes between three minority groups-African Americans (AAs), Hispanics, and American Indians (AIs) versus non-Hispanic Whites (NHWs), as the referent group, in separate cohorts. Separate cross-sectional evaluations were performed of three US-based cohorts of subjects at risk for COPD: COPDGene Study with 6,884 NHW and 3,416 AA smokers; Lovelace Smokers' Cohort with 1,598 NHW and 378 Hispanic smokers; and Mining Dust Exposure in the United States Cohort with 2,115 NHW, 2,682 Hispanic, and 2,467 AI miners. Prebronchodilator spirometry tests were performed at baseline visits using standard criteria. The primary outcome was the prevalence of airflow obstruction. Secondary outcomes were self-reported physician diagnosis of COPD, chronic bronchitis, and modified Medical Research Council dyspnea score. All minority groups had a lower prevalence of airflow obstruction than NHWs (adjusted ORs varied from 0.29 in AIs to 0.85 in AAs; p < 0.01 for all analyses). AAs had a lower prevalence of chronic bronchitis than NHWs. In our study, all minority groups had a lower prevalence of airflow obstruction but a greater level of self-reported dyspnea than NHWs, and covariates did not explain this association. A better understanding of racial and ethnic differences in smoking-related and occupational airflow obstruction may improve prevention and therapeutic strategies.

Ethnic Variance in Prevalence of COPD among Smokers in a Real World Setting

INTRODUCTION

Chronic Obstructive Pulmonary Disease (COPD) is characterized by persistent and progressive airflow limitation generally caused by prolonged cigarette smoking. Ethnic differences have been reported regarding COPD risk from smoking. The purpose of this study was to compare COPD prevalence in Hispanic and Caucasian smokers in a real-world setting. We studied consecutive patients referred to the community-based pulmonary practice. Hispanic and Caucasian smokers were included in the study.

METHODS

The clinical diagnosis of COPD was recorded from the chart. COPD was defined by PFT using GOLD criteria. Exclusion criteria were other ethnicities, non-smokers, and patients with a history of asthma /other pulmonary conditions. We reviewed a total of 1,313 consecutive PFTs of which 797 patients met our inclusion criteria.

RESULTS AND DISCUSSION

The prevalence of COPD among Hispanics was found to be lower by both clinical diagnosis as well as by spirometry compared to Caucasians (41.6% vs 54.2%). In Hispanics, clinical diagnosis was 91% higher by PFT, whereas for Caucasians, it was 6% lower. The odds of developing COPD (diagnosed based on FEV1/FVC ratio <70%) in the Caucasians are 4.1 times higher than Hispanics (Odds Ratio: 4.1; 95%CI: 2.8-5.9). Hispanic smokers have a lower prevalence of COPD both by the clinical diagnosis as well as by PFT. There is a significant disconnection between clinical and PFT diagnosis of COPD in Hispanic patients.

CONCLUSION

The genetic basis of lower COPD risk and prevalence in Hispanics needs to be better understood. Spirometry threshold criteria for confirming a diagnosis of COPD may need to be modified based on ethnicity in clinical practice.

Resting-State Connectivity in Former, Current, and Never Smokers

INTRODUCTION

Understanding the neural mechanisms that support successful smoking cessation is vital to the development of novel treatments for nicotine dependence.

METHOD

To this end, we compared resting-state functional connectivity across three smoking groups: current, never, and former smokers. We used an independent component analysis (ICA) that allowed us to compare differences in intrinsic, large-scale networks across our groups. Using this technique, we were able to compare group differences across resting-state networks without the requirement of identifying coordinate-based regions of interest.

RESULTS

Overall, the ICA resulted in networks that were largely consistent with previous reports, including bilateral executive control networks, salience, and a default mode network. Group comparisons among the three groups revealed differences in three networks including sensorimotor, dorsal attention, and default mode networks, with differences localized to pre/postcentral gyrus, lateral occipital cortex, and superior parietal lobe. In all regions showing a difference, current smokers showed increased network amplitude compared to former and never smokers.

CONCLUSION

Although some theoretical models of recovery have suggested an important role of frontal cortex and cognitive control, the current results seem to suggest that reductions in posterior regions including superior parietal lobe and somatosensory cortex may play a key role in maintaining long-term abstinence from cigarettes.

IMPLICATIONS

The submitted research is a novel contribution to the study of successful nicotine abstinence, in part, because it includes individuals who have successfully overcome nicotine dependence. The use of ICA allowed for examination of large-scale resting-state networks throughout the brain without the need for specifying numerous regions of interest. This research supports the view that overcoming nicotine dependence may depend on reducing spontaneous activity in posterior regions of the brain rather than solely enhancing frontal control.

The Challenge of Controlling the COPD Epidemic: Unmet Needs

Many unmet needs still remain in the assessment and treatment of patients with chronic obstructive pulmonary disease (COPD), particularly in relation to its under- and misdiagnosis, which lead to under- and mistreatment. This paucity of knowledge about the importance and presence of COPD, as well as its treatment, is seen among patients and carers as well as health care providers. This review considers areas of key educational need, including the clinical characteristics of COPD; factors that contribute to the disease, effective diagnosis, and clinical management of patients; and the implementation of treatment guidelines. As COPD remains the third most frequent cause of death in the world, researchers must continue to expand the scope and reach of their efforts to improve outcomes of this debilitating disease.

A Pilot Study Linking Endothelial Injury in Lungs and Kidneys in Chronic Obstructive Pulmonary Disease

RATIONALE

Patients with chronic obstructive pulmonary disease (COPD) frequently have albuminuria (indicative of renal endothelial cell injury) associated with hypoxemia.

OBJECTIVES

To determine whether (1) cigarette smoke (CS)-induced pulmonary and renal endothelial cell injury explains the association between albuminuria and COPD, (2) CS-induced albuminuria is linked to increases in the oxidative stress-advanced glycation end products (AGEs) receptor for AGEs (RAGE) pathway, and (3) enalapril (which has antioxidant properties) limits the progression of pulmonary and renal injury by reducing activation of the AGEs-RAGE pathway in endothelial cells in both organs.

METHODS

In 26 patients with COPD, 24 ever-smokers without COPD, 32 nonsmokers who underwent a renal biopsy or nephrectomy, and in CS-exposed mice, we assessed pathologic and ultrastructural renal lesions, and measured urinary albumin/creatinine ratios, tissue oxidative stress levels, and AGEs and RAGE levels in pulmonary and renal endothelial cells. The efficacy of enalapril on pulmonary and renal lesions was assessed in CS-exposed mice.

MEASUREMENTS AND MAIN RESULTS

Patients with COPD and/or CS-exposed mice had chronic renal injury, increased urinary albumin/creatinine ratios, and increased tissue oxidative stress and AGEs-RAGE levels in pulmonary and renal endothelial cells. Treating mice with enalapril attenuated CS-induced increases in urinary albumin/creatinine ratios, tissue oxidative stress levels, endothelial cell AGEs and RAGE levels, pulmonary and renal cell apoptosis, and the progression of chronic renal and pulmonary lesions.

CONCLUSIONS

Patients with COPD and/or CS-exposed mice have pulmonary and renal endothelial cell injury linked to increased endothelial cell AGEs and RAGE levels. Albuminuria could identify patients with COPD in whom angiotensin-converting enzyme inhibitor therapy improves renal and lung function by reducing endothelial injury.

Spirometric variability in smokers: transitions in COPD diagnosis in a five-year longitudinal study

Background

Spirometrically-defined chronic obstructive pulmonary disease (COPD) is considered progressive but its natural history is inadequately studied. We hypothesized that spirometrically-defined COPD states could undergo beneficial transitions.

Methods

Participants in the Lovelace Smokers’ Cohort (n = 1553), primarily women, were longitudinally studied over 5 years. Spirometric states included normal postbronchodilator spirometry, COPD Stage I, Unclassified state, and COPD Stage II+, as defined by GOLD guidelines. Beneficial transitions included either a decrease in disease severity, including resolution of spirometric abnormality, or maintenance of non-diseased state. ‘All smokers’ (n = 1553) and subgroups with normal and abnormal spirometry at baseline (n = 956 and 597 respectively) were separately analyzed. Markov-like model of transition probabilities over an average follow-up period of 5 years were calculated.

Results

Among ‘all smokers’, COPD Stage I, Unclassified, and COPD Stage II+ states were associated with probabilities of 16, 39, and 22 % respectively for beneficial transitions, and of 16, 35, and 4 % respectively for resolution. Beneficial transitions were more common for new-onset disease than for pre-existing disease (p < 0.001). Beneficial transitions were less common among older smokers, men, or those with bronchial hyperresponsiveness but more common among Hispanics and smokers with excess weight.

Conclusions

This observational study of ever smokers, shows that spirometrically-defined COPD states, may not be uniformly progressive and can improve or resolve over time. The implication of these findings is that the spirometric diagnosis of COPD can be unstable. Furthermore, COPD may have a pre-disease state when interventions might help reverse or change its natural history.

Trial registration

NA.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0468-7) contains supplementary material, which is available to authorized users.

Differences in Health-Related Quality of Life Between New Mexican Hispanic and Non-Hispanic White Smokers

BACKGROUND

Smoking is associated with impaired health-related quality of life (HRQL) across all populations. Because decline in lung function and risk for COPD are lower in New Mexican Hispanic smokers compared with their non-Hispanic white (NHW) counterparts, the goal of this study was to ascertain whether HRQL differs between these two racial/ethnic groups and determine the factors that contribute to this difference.

METHODS

We compared the score results of the Medical Outcomes Short-Form 36 Health Survey (SF-36) and St. George's Respiratory Questionnaire (SGRQ) in 378 Hispanic subjects and 1,597 NHW subjects enrolled in the Lovelace Smokers' Cohort (LSC) from New Mexico. The associations of race/ethnicity with SGRQ and SF-36 were assessed by using multivariable regression.

RESULTS

Physical functioning (difference, -4.5; P = .0008) but not mental health or role emotional domains of the SF-36 was worse in Hispanic smokers than in their NWH counterparts in multivariable analysis. SGRQ total score and its activity and impact subscores were worse in Hispanic (vs NHW) smokers after adjustment for education level, current smoking, pack-years smoked, BMI, number of comorbidities, and FEV₁ % predicted (difference range, 2.9-5.0; all comparisons, P ≤ .001). Although the difference in the SGRQ activity domain was above the clinically important difference of four units, the total score was not.

CONCLUSIONS

New Mexican Hispanic smokers have clinically relevant, lower HRQL than their NHW counterparts. A perception of diminished physical functioning and impairment in daily life activities contribute to the poorer HRQL among Hispanic subjects.

A genome-wide association study of chronic obstructive pulmonary disease in Hispanics

RATIONALE

Genome-wide association studies (GWAS) of chronic obstructive pulmonary disease (COPD) have identified disease-susceptibility loci, mostly in subjects of European descent.

OBJECTIVES

We hypothesized that by studying Hispanic populations we would be able to identify unique loci that contribute to COPD pathogenesis in Hispanics but remain undetected in GWAS of non-Hispanic populations.

METHODS

We conducted a metaanalysis of two GWAS of COPD in independent cohorts of Hispanics in Costa Rica and the United States (Multi-Ethnic Study of Atherosclerosis [MESA]). We performed a replication study of the top single-nucleotide polymorphisms in an independent Hispanic cohort in New Mexico (the Lovelace Smokers Cohort). We also attempted to replicate prior findings from genome-wide studies in non-Hispanic populations in Hispanic cohorts.

MEASUREMENTS AND MAIN RESULTS

We found no genome-wide significant association with COPD in our metaanalysis of Costa Rica and MESA. After combining the top results from this metaanalysis with those from our replication study in the Lovelace Smokers Cohort, we identified two single-nucleotide polymorphisms approaching genome-wide significance for an association with COPD. The first (rs858249, combined P value = 6.1 × 10(-8)) is near the genes KLHL7 and NUPL2 on chromosome 7. The second (rs286499, combined P value = 8.4 × 10(-8)) is located in an intron of DLG2. The two most significant single-nucleotide polymorphisms in FAM13A from a previous genome-wide study in non-Hispanics were associated with COPD in Hispanics.

CONCLUSIONS

We have identified two novel loci (in or near the genes KLHL7/NUPL2 and DLG2) that may play a role in COPD pathogenesis in Hispanic populations.

Chronic Bronchitis Is Associated With Worse Symptoms and Quality of Life Than Chronic Airflow Obstruction

BACKGROUND

COPD includes the chronic bronchitis (CB) and emphysema phenotypes. Although it is generally assumed that emphysema or chronic airflow obstruction (CAO) is associated with worse quality of life (QOL) than is CB, this assumption has not been tested.

METHODS

The current study's analyses from the Lovelace Smokers' Cohort (LSC) were validated in the COPD Gene Cohort (COPDGene). CB without CAO (CB only) was defined as self-reported cough productive of phlegm for ≥ 3 mo/y for 2 consecutive years and postbronchodilator FEV1/FVC ≥ 70%. CAO without CB (CAO only) was defined as a postbronchodilator FEV1/FVC < 70% with no evidence of CB. QOL outcomes were obtained from the St. George's Respiratory Questionnaire (SGRQ) and the 36-Item Short Form Health Survey (SF-36) questionnaires. A priori covariates included age, sex, pack-years of smoking, current smoking, and FEV1.

RESULTS

Smokers with CB without CAO (LSC = 341; COPDGene = 523) were younger and had a greater BMI and less smoking exposure than did those with CAO only (LSC = 302; COPDGene = 2,208). Compared with the latter group, QOL scores were worse for those with CB only. Despite similar SGRQ Activity and SF-36 Role Physical and Physical Functioning, SGRQ Symptoms and Impact scores and SF-36 emotional and social measures were worse in the CB-only group, in both cohorts. After adjustment for covariates, the CB-only group remained a significant predictor for "worse" symptoms and emotional and social measures.

CONCLUSIONS

To our knowledge, this analysis is the first to suggest that among subjects with COPD, those with CB only present worse QOL symptoms and mental well-being than do those with CAO only.

Spirometry and health status worsen with weight gain in obese smokers but improve in normal-weight smokers

RATIONALE

The literature on the effect of obesity and weight gain on respiratory outcomes in smokers is contradictory.

OBJECTIVE

To examine the cross-sectional effect of body mass index (BMI) and the longitudinal effect of change in BMI upon spirometry and health status among smokers at risk for and with milder chronic obstructive pulmonary disease (COPD).

METHODS

Participants from the Lovelace Smokers' Cohort were followed for a median period of 6 years, 75% of whom were at risk and 25% of whom had COPD at baseline examination. BMI and gain in BMI were examined as continuous independent variables overall and after stratification into three categories (normal-weight, overweight, and obese) determined on the basis of baseline weight. Spirometry and health status (as assessed by St. George Respiratory Questionnaire total and subscale scores) were dependent variables. Covariates included age, sex, ethnicity, pack-years of smoking, and current smoking status. Cross-sectional analysis used linear and logistic regression; longitudinal analysis used a mixed model approach.

MEASUREMENTS AND MAIN RESULTS

In cross-sectional analyses, higher BMI was associated with worse health status among obese smokers but with better health status among normal-weight smokers. In longitudinal analyses, weight gain was associated with a decrease in FEV1 and health status among obese smokers and with an increase in these outcomes among normal-weight smokers.

CONCLUSIONS

Weight gain affects respiratory outcomes differently between obese and normal-weight smokers. Whereas FEV1 and health status decrease with weight gain among obese smokers, they improve among normal-weight smokers. The nonlinear relationship between weight gain and respiratory outcomes suggests that this effect of excess weight is unlikely to be mechanical alone.

Rapid lung function decline in smokers is a risk factor for COPD and is attenuated by angiotensin-converting enzyme inhibitor use

OBJECTIVE

Cigarette smoking is the most important risk factor for COPD in the United States. Host factors that influence the rapid rate of FEV1 decline in smokers and how decline rate influences risk for developing COPD are unknown. The aim of this study was to characterize the rate of FEV1 decline in ever smokers, compare the risk of incident COPD between those with rapid decline and others, and determine the effect of selected drugs on rapid decline.

METHODS

A total of 1,170 eligible ever smokers from the longitudinal Lovelace Smokers Cohort with repeat spirometry tests over a minimum follow-up period of 3 years (mean follow-up, 5.9 years) were examined, including 809 ever smokers without a spirometric abnormality at baseline. Longitudinal absolute decline in postbronchodilator FEV1 from the slope of the spirometric values over all examinations was annualized and classified as rapid (≥30 mL/y), normal (0-29.9 mL/y), or no (>0 mL/y) decline. Logistic regression and Kaplan-Meier survival curves were used for the analysis.

RESULTS

Approximately 32% of ever smokers exhibited rapid decline. Among ever smokers without a baseline spirometric abnormality, rapid decline was associated with an increased risk for incident COPD (OR, 1.88; P=.003). The use of angiotensin-converting enzyme (ACE) inhibitors at baseline examination was protective against rapid decline, particularly among those with comorbid cardiovascular disease, hypertension, or diabetes (ORs 0.48, 0.48, and 0.12, respectively; P≤.02 for all analyses).

CONCLUSIONS

Ever smokers with a rapid decline in FEV1 are at higher risk for COPD. Use of ACE inhibitors by smokers may protect against this rapid decline and the progression to COPD.

Obstructive lung disease in Mexican Americans and non-Hispanic whites: an analysis of diagnosis and survival in the National Health and Nutritional Examination Survey III Follow-up Study

BACKGROUND

Although obstructive lung disease (OLD), which includes COPD, affects all the populations, Hispanics seem to be protected against COPD development and progression. Whether this advantage translates into a survival benefit for this population is unknown. We aimed to determine the risk for OLD in Mexican Americans, the largest US Hispanic subgroup, compared with non-Hispanic whites and to assess all-cause mortality in subjects with OLD.

METHODS

We assessed the relationships between Mexican American ethnicity and spirometric OLD and risk of death among 6,456 US adults aged ≥ 40 years who participated in the Third National Health and Nutritional Examination Survey Follow-up Study. We used logistic and Cox regression analyses to estimate the OR for OLD among Mexican Americans and the hazard ratio (HR) for all-cause mortality among Mexican Americans with OLD, respectively.

RESULTS

After adjustment for demographic factors, socioeconomic status, and COPD risk factors, Mexican Americans had decreased odds of OLD diagnosis compared with whites (OR, 0.72 [95% CI, 0.54-0.95]). Among the 1,734 participants with OLD, 1,054 (60.8%) died during median follow-up of 12 years. In an adjusted model, Mexican Americans had no advantage in mortality from all causes (HR, 0.88 [95% CI, 0.69-1.13]). After accounting for the fact that some Mexican Americans may have moved back to Mexico and died there (thus, had no US death certificate), there was still no difference in mortality between these groups.

CONCLUSIONS

Although Mexican Americans appear to have lower risk for OLD, subjects of this ethnicity with OLD do not seem to have a survival advantage.

Methylated Genes in Sputum Among Older Smokers With Asthma

OBJECTIVE

The epigenetic basis for human asthma is not well studied, particularly among older adults. This study investigated the methylation profiles in sputum DNA among older adults with asthma, using a population of smokers.

METHODS

This was a cross-sectional study using the Lovelace Smokers Cohort, a population of former and current smokers aged ≥ 40 years in New Mexico. One hundred eighty-four smokers with asthma were compared with 511 smoker control subjects with a similar smoking history, after carefully excluding those with COPD. Environmental exposures were assessed by a standard questionnaire. Postbronchodilator spirometry was performed. Induced sputum was analyzed for the methylation prevalence of 12 selected asthma-related genes using nested methylation-specific polymerase chain reaction assay.

RESULTS

Asthma was associated with a greater number of methylated genes and, specifically, with methylated protocadherin-20 gene in sputum DNA compared with control subjects with a similar smoking history. These associations remained significant after adjustment for covariates as well as Bonferroni correction. A synergistic interaction was noted between two methylated genes (protocadherin-20 and paired box protein transcription factor-5α) in sputum DNA on the odds for asthma (P = .009). Interestingly, the epigenetic-asthma associations were not explained by the environmental factors studied. Further, methylated genes in sputum DNA, including the protocadherin-20 gene, identified a symptomatically more severe asthma phenotype in a subgroup analysis.

CONCLUSIONS

Asthma is associated with methylation of selected genes, such as protocadherin-20 gene, in sputum DNA. If future studies establish causality, novel demethylating interventions to prevent and treat asthma among older smokers may be possible.

Identification of FGF7 as a novel susceptibility locus for chronic obstructive pulmonary disease

RATIONALE

Traditional genome-wide association studies (GWASs) of large cohorts of subjects with chronic obstructive pulmonary disease (COPD) have successfully identified novel candidate genes, but several other plausible loci do not meet strict criteria for genome-wide significance after correction for multiple testing.

OBJECTIVES

The authors hypothesise that by applying unbiased weights derived from unique populations we can identify additional COPD susceptibility loci. Methods The authors performed a homozygosity haplotype analysis on a group of subjects with and without COPD to identify regions of conserved homozygosity haplotype (RCHHs). Weights were constructed based on the frequency of these RCHHs in case versus controls, and used to adjust the p values from a large collaborative GWAS of COPD.

RESULTS

The authors identified 2318 RCHHs, of which 576 were significantly (p<0.05) over-represented in cases. After applying the weights constructed from these regions to a collaborative GWAS of COPD, the authors identified two single nucleotide polymorphisms (SNPs) in a novel gene (fibroblast growth factor-7 (FGF7)) that gained genome-wide significance by the false discovery rate method. In a follow-up analysis, both SNPs (rs12591300 and rs4480740) were significantly associated with COPD in an independent population (combined p values of 7.9E-7 and 2.8E-6, respectively). In another independent population, increased lung tissue FGF7 expression was associated with worse measures of lung function.

CONCLUSION

Weights constructed from a homozygosity haplotype analysis of an isolated population successfully identify novel genetic associations from a GWAS on a separate population. This method can be used to identify promising candidate genes that fail to meet strict correction for multiple testing.

New Mexican Hispanic smokers have lower odds of chronic obstructive pulmonary disease and less decline in lung function than non-Hispanic whites

RATIONALE

The epidemiology of cigarette smoking-related chronic obstructive pulmonary disease (COPD) is not well characterized in Hispanics in the United States. Understanding how ethnicity influences COPD is important for a number of reasons, from informing public health policies to dissecting the genetic and environmental effects that contribute to disease.

OBJECTIVES

The present study assessed differences in risk between Hispanics and non-Hispanic whites for longitudinal and cross-sectional COPD phenotypes. Genetic ancestry was used to verify findings based on self-reported ethnicity. Hispanics in New Mexico are primarily differentiated from non-Hispanic whites by their proportion of Native American ancestry.

METHODS

The study was performed in a New Mexican cohort of current and former smokers. Self-reported Hispanic and non-Hispanic white ethnicity was validated by defining genetic ancestry proportions at the individual level using 48 single-nucleotide polymorphism markers. Self-reported ethnicity and genetic ancestry were independently used to assess associations with cross-sectional and longitudinal measures of lung function. Multivariable models were adjusted for indicators of smoking behavior.

MEASUREMENTS AND MAIN RESULTS

Self-reported Hispanic ethnicity was significantly associated with lower odds of COPD (odds ratio, 0.49; 95% confidence interval, 0.35-0.71; P = 0.007), and this protection was validated by the observation that Hispanic smokers have reduced risk of rapid decline in lung function (odds ratio, 0.48; 95% confidence interval, 0.30-0.78; P = 0.003). Similar findings were noted when Native American genetic ancestry proportions were used as predictors instead of self-report of Hispanic ethnicity.

CONCLUSIONS

Hispanic ethnicity is inversely associated with cross-sectional and longitudinal spirometric COPD phenotypes even after adjustment for smoking. Native American genetic ancestry may account for this "Hispanic protection."

Wood smoke exposure and gene promoter methylation are associated with increased risk for COPD in smokers

RATIONALE

Wood smoke-associated chronic obstructive pulmonary disease (COPD) is common in women in developing countries but has not been adequately described in developed countries.

OBJECTIVES

Our objective was to determine whether wood smoke exposure was a risk factor for COPD in a population of smokers in the United States and whether aberrant gene promoter methylation in sputum may modify this association.

METHODS

For this cross-sectional study, 1,827 subjects were drawn from the Lovelace Smokers' Cohort, a predominantly female cohort of smokers. Wood smoke exposure was self-reported. Postbronchodilator spirometry was obtained, and COPD outcomes studied included percent predicted FEV₁, airflow obstruction, and chronic bronchitis. Effect modification of wood smoke exposure with current cigarette smoke, ethnicity, sex, and promoter methylation of lung cancer-related genes in sputum on COPD outcomes were separately explored. Multivariable logistic and poisson regression models were used for binary and rate-based outcomes, respectively.

MEASUREMENTS AND MAIN RESULTS

Self-reported wood smoke exposure was independently associated with a lower percent predicted FEV₁ (point estimate [± SE] -0.03 ± 0.01) and a higher prevalence of airflow obstruction and chronic bronchitis (odds ratio, 1.96; 95% confidence interval, 1.52-2.52 and 1.64 (95% confidence interval, 1.31-2.06, respectively). These associations were stronger among current cigarette smokers, non-Hispanic whites, and men. Wood smoke exposure interacted in a multiplicative manner with aberrant promoter methylation of the p16 or GATA4 genes on lower percent predicted FEV₁.

CONCLUSIONS

These studies identify a novel link between wood smoke exposure and gene promoter methylation that synergistically increases the risk for reduced lung function in cigarette smokers.

Wood smoke exposure and gene promoter methylation are associated with increased risk for COPD in smokers

RATIONALE

Wood smoke-associated chronic obstructive pulmonary disease (COPD) is common in women in developing countries but has not been adequately described in developed countries.

OBJECTIVES

Our objective was to determine whether wood smoke exposure was a risk factor for COPD in a population of smokers in the United States and whether aberrant gene promoter methylation in sputum may modify this association.

METHODS

For this cross-sectional study, 1,827 subjects were drawn from the Lovelace Smokers' Cohort, a predominantly female cohort of smokers. Wood smoke exposure was self-reported. Postbronchodilator spirometry was obtained, and COPD outcomes studied included percent predicted FEV₁, airflow obstruction, and chronic bronchitis. Effect modification of wood smoke exposure with current cigarette smoke, ethnicity, sex, and promoter methylation of lung cancer-related genes in sputum on COPD outcomes were separately explored. Multivariable logistic and poisson regression models were used for binary and rate-based outcomes, respectively.

MEASUREMENTS AND MAIN RESULTS

Self-reported wood smoke exposure was independently associated with a lower percent predicted FEV₁ (point estimate [± SE] -0.03 ± 0.01) and a higher prevalence of airflow obstruction and chronic bronchitis (odds ratio, 1.96; 95% confidence interval, 1.52-2.52 and 1.64 (95% confidence interval, 1.31-2.06, respectively). These associations were stronger among current cigarette smokers, non-Hispanic whites, and men. Wood smoke exposure interacted in a multiplicative manner with aberrant promoter methylation of the p16 or GATA4 genes on lower percent predicted FEV₁.

CONCLUSIONS

These studies identify a novel link between wood smoke exposure and gene promoter methylation that synergistically increases the risk for reduced lung function in cigarette smokers.

MMP12, lung function, and COPD in high-risk populations

BACKGROUND

Genetic variants influencing lung function in children and adults may ultimately lead to the development of chronic obstructive pulmonary disease (COPD), particularly in high-risk groups.

METHODS

We tested for an association between single-nucleotide polymorphisms (SNPs) in the gene encoding matrix metalloproteinase 12 (MMP12) and a measure of lung function (prebronchodilator forced expiratory volume in 1 second [FEV(1)]) in more than 8300 subjects in seven cohorts that included children and adults. Within the Normative Aging Study (NAS), a cohort of initially healthy adult men, we tested for an association between SNPs that were associated with FEV(1) and the time to the onset of COPD. We then examined the relationship between MMP12 SNPs and COPD in two cohorts of adults with COPD or at risk for COPD.

RESULTS

The minor allele (G) of a functional variant in the promoter region of MMP12 (rs2276109 [-82A-->G]) was positively associated with FEV(1) in a combined analysis of children with asthma and adult former and current smokers in all cohorts (P=2x10(-6)). This allele was also associated with a reduced risk of the onset of COPD in the NAS cohort (hazard ratio, 0.65; 95% confidence interval [CI], 0.46 to 0.92; P=0.02) and with a reduced risk of COPD in a cohort of smokers (odds ratio, 0.63; 95% CI, 0.45 to 0.88; P=0.005) and among participants in a family-based study of early-onset COPD (P=0.006).

CONCLUSIONS

The minor allele of a SNP in MMP12 (rs2276109) is associated with a positive effect on lung function in children with asthma and in adults who smoke. This allele is also associated with a reduced risk of COPD in adult smokers.