Sex differences in severe pulmonary emphysema

Sex-Related Differences in Pulmonary Function following 6 Months of Cigarette Exposure: Implications for Sexual Dimorphism in Mild COPD

Female smokers have increased risk of chronic obstructive pulmonary disease (COPD) compared with male smokers who have a similar history of cigarette smoke exposure. We have shown previously that chronic smoke exposure for 6 months leads to increased airway wall remodeling in female C57BL/6 mice compared with male C57BL/6 mice. These differences, however, were not evident in female ovariectomized mice exposed to cigarette smoke. Herein, we report on the pulmonary function test results from the flexiVent system, which was used to determine the potential functional consequences of the histologic changes observed in these mice. We found that tissue damping (G) was increased in female compared to male or ovariectomized female mice after smoke exposure. At low oscillating frequencies, complex input resistance (Zrs) and impedance (Xrs) of the respiratory system was increased and decreased, respectively, in female but not in male or ovariectomized female mice after smoke exposure. Quasistatic pressure-volume curves revealed a reduction in inspiratory capacity in female mice but not in male or ovariectomized female mice after smoke exposure. The remaining lung function measurements including quasistatic compliance were similar amongst all groups. This is the first study characterizing a sexual dimorphism in respiratory functional properties in a mouse model of COPD. These findings demonstrate that increased airway remodeling in female mice following chronic smoke exposure is associated with increased tissue resistance in the peripheral airways. These data may explain the importance of female sex hormones and the increased risk of airway disease in female smokers.

Current Smoking Status Is Associated With Lower Quantitative CT Measures of Emphysema and Gas Trapping

PURPOSE

The purposes of this study were to evaluate the effect of smoking status on quantitative computed tomography CT measures of low-attenuation areas (LAAs) on inspiratory and expiratory CT and to provide a method of adjusting for this effect.

MATERIALS AND METHODS

A total of 6762 current and former smokers underwent spirometry and volumetric inspiratory and expiratory CT. Quantitative CT analysis was completed using open-source 3D Slicer software. LAAs were defined as lung voxels with attenuation values ≤-950 Hounsfield units (HU) on inspiratory CT and ≤-856 HU on expiratory CT and were expressed as percentage of CT lung volume (%LAAI-950 and %LAAE-856). Multiple linear regression was used to determine the effect of smoking status on %LAAI-950 and %LAAE-856 while controlling for demographic variables, spirometric lung function, and smoking history, as well as total lung capacity (%LAAI-950) or functional residual capacity (%LAAE-856). Quantile normalization was used to align the %LAAI-950 distributions for current and former smokers.

RESULTS

Mean %LAAI-950 was 4.2±7.1 in current smokers and 7.7±9.7 in former smokers (P<0.001). After adjusting for confounders, %LAAI-950 was 3.5 percentage points lower and %LAAE-856 was 6.0 percentage points lower in current smokers than in former smokers (P<0.001). After quantile normalization, smoking status was an insignificant variable in the inspiratory regression model, with %LAAI-950 being 0.27 percentage points higher in current smokers (P=0.13).

CONCLUSIONS

After adjusting for patient demographics and lung function, current smokers display significantly lower %LAAI-950 and %LAAE-856 than do former smokers. Potential methods for adjusting for this effect would include adding a fixed value (eg, 3.5%) to the calculated percentage of emphysema in current smokers, or quantile normalization.

Sex Differences in Airway Remodeling in a Mouse Model of Chronic Obstructive Pulmonary Disease

RATIONALE

After adjustment for the amount of smoking, women have a 50% increased risk of chronic obstructive pulmonary disease (COPD) compared with men. The anatomic basis and/or mechanism(s) of these sex-related differences in COPD are unknown.

OBJECTIVES

To characterize the impact of female sex hormones on chronic cigarette smoke-induced airway remodeling and emphysema in a mouse model of COPD.

METHODS

Airway remodeling and emphysema were determined morphometrically in male, female, and ovariectomized mice exposed to 6 months of cigarette smoke. Antioxidant- and transforming growth factor (TGF)-β-related genes were profiled in airway tissues. The selective estrogen receptor modulator tamoxifen was also administered during smoke exposure in a short-term model. Airway wall thickness of male and female human smokers at risk of or with mild COPD was measured using optical coherence tomography.

MEASUREMENTS AND MAIN RESULTS

Small airway wall remodeling was increased in female but not male or ovariectomized mice and was associated with increased distal airway resistance, down-regulation of antioxidant genes, increased oxidative stress, and activation of TGF-β1. These effects were prevented by ovariectomy. Use of tamoxifen as a therapeutic intervention mitigated smoke-induced increase in oxidative stress in female mice. Compared with male human smokers, female human smokers had significantly thicker airway walls.

CONCLUSIONS

The excess risk of small airway disease in female mice after chronic smoke exposure was associated with increased oxidative stress and TGF-β1 signaling and also was related to the effects of female sex hormones. Estrogen receptor antagonism might be of value in reducing oxidative stress in female smokers.

Sex Difference in Chronic Obstructive Lung Disease. Does it Matter? A Concise Review

Chronic obstructive lung disease (COPD) primarily affects men; however, its epidemiology has been changing because more women have become smokers. Recently, investigators found that although women and men were exposed to the same amount of smoke fume, women tended to have more severe disease and higher mortality rate. They also complain of more dyspnoea and may experience more severe exacerbations than men. This led to the question of whether sex has an impact on COPD course and whether women have a higher susceptibility to smoke fumes than men. That may be explained by multiple complex factors highlighting the relationship between sex, epidemiology, method of diagnostics and the clinical course of the disease. In this review, sex differences in epidemiology, clinical presentation, exacerbation, co-morbidities and treatment are covered.

Association of plasma adipokines with chronic obstructive pulmonary disease severity and progression

RATIONALE

Two adipokines, leptin and adiponectin, regulate metabolic and inflammatory systems reciprocally. The role of adiponectin in chronic obstructive pulmonary disease (COPD) has been studied. However, there are few data evaluating the relationship of plasma leptin with COPD severity or progression.

OBJECTIVES

The objective of this study was to evaluate the relationship of leptin, adiponectin, and the leptin/adiponectin ratio with COPD severity and progression according to COPD phenotypes.

METHODS

Plasma leptin and adiponectin levels were measured in 196 subjects with COPD selected from the Korean Obstructive Lung Disease cohort. Using a linear regression model and mixed linear regression, we determined the relationship of plasma leptin and adiponectin levels and the leptin/adiponectin ratio to COPD severity and progression over 3 years.

MEASUREMENTS AND MAIN RESULTS

The concentration of adiponectin in plasma positively correlated with percent emphysema on initial computed tomography (CT) (adjusted P = 0.022), whereas plasma leptin concentrations and the leptin/adiponectin ratio exhibited a significant inverse correlation with initial FEV1 (adjusted P = 0.013 for leptin and adjusted P = 0.041 for leptin/adiponectin ratio). Increased plasma leptin and leptin/adiponectin ratio were significantly associated with change in percent emphysema over 3 years (adjusted P = 0.037 for leptin and adjusted P = 0.029 for leptin/adiponectin ratio), whereas none of the adipokines demonstrated an association with FEV1 decline over the 3-year period.

CONCLUSIONS

Plasma adiponectin and leptin vary according to COPD phenotypes. Plasma leptin and the leptin/adiponectin ratio, but not adiponectin, were significantly associated with changes in CT-assessed emphysema, suggesting a potential role as a biomarker in emphysema progression in patients with COPD.

Emphysema prevalence related air pollution caused by a cement plant

Background

To identify adverse pulmonary health effects due to air pollution derived from a cement plant in Korea. The emphysema prevalence in residents around a cement plant was compared to that in the group who live far away from the plant by chest films (PA and lateral view) and high-resolution computed tomography (HRCT) lung images.

Methods

From June to August in 2013 and from August to November in 2014, chest films and HRCT scan were conducted on residents over the age of 40 who lived around a cement plant. The residents were divided into two groups; a “more exposed group (MEG)” which consisted of 1,046 people who lived within a 1 km radius and a “less exposed group (LEG)” which consisted of 317 people who lived more than 5 km away from the same plant. We compared the emphysema prevalence and estimated the OR of this between the MEG and the LEG by using a chi-square and logistic regression on chest films and HRCT.

Results

The emphysema prevalence was 9.1 % in the LEG, 14.3 % in the MEG on chest films and 11.4 %, 17.8 % on the HRCT, respectively. The OR of the emphysema prevalence in MEG was 2.92 (95 % CI 1.77-4.83) on the chest films, 2.56 (95 % CI 1.64–3.99) on the HRCT after sex, age, body mass index (BMI), smoking history, residency period and firewood used history were adjusted. The OR in the less than 29 pack-years smoking history was 1.66 (95 % CI 0.92–3.06) and in the more than 30 pack-years was 3.05 (95 % CI 1.68–5.52) on the chest films, and was 1.68 (95 % CI 0.98–2.90), 2.93 (95 % CI 1.72–4.98) on the HRCT, respectively.

Conclusion

The emphysema prevalence seems to be affected by the level of exposure to air pollution derived from the cement plant as well as sex, age, BMI, and smoking history in this study. Moreover, the OR of the case of the more exposed to the air pollution was similar to that of the case in smoking.

Prevalence of thoracic pain in patients with chronic obstructive pulmonary disease and relationship with patient characteristics: a cross-sectional observational study

BACKGROUND

Objectives of this study were to evaluate the prevalence of thoracic pain in patients with chronic obstructive pulmonary disease (COPD) and its relationship with Forced Expiratory Volume in the first second (FEV1), static hyperinflation, dyspnoea, functional exercise capacity, disease-specific health status, anxiety, and depression.

METHODS

This cross-sectional observational study included patients with COPD entering pulmonary rehabilitation. Participants underwent spirometry, plethysmography, and measurement of single breath diffusion capacity. Pain was assessed using a multidimensional, structured pain interview. In addition, dyspnoea severity (Modified Medical Research Council Dyspnoea Scale (mMRC)), functional exercise capacity (six-minute walking distance (6MWD)), disease-specific health status (COPD Assessment Test (CAT)), and symptoms of anxiety and depression (Hospital Anxiety Depression Scale (HADS)) were recorded.

RESULTS

55 of the included 67 participants reported chronic pain (82.1%). 53.7% had thoracic pain. After considering multiple comparisons, only younger age and worse CAT scores were related with the presence of thoracic pain (p = 0.01). There were no relationships between thoracic pain and FEV1, static lung hyperinflation, diffusion capacity, mMRC score, 6MWD, anxiety or depression.

CONCLUSION

Thoracic pain is highly prevalent in COPD patients and is related to impaired disease-specific health status, but there is no relationship with FEV1, static hyperinflation, dyspnoea severity or functional exercise capacity.

Mother's smoking and complex lung function of offspring in middle age: A cohort study from childhood

BACKGROUND AND OBJECTIVE

Existing evidence that supports maternal smoking to be a potential risk factor for chronic obstructive pulmonary disease (COPD) for adult offspring has barely been mentioned in major guideline documents, suggesting a need for more robust and consistent data. We aimed to examine whether such early life exposure can predispose to COPD in middle age, possibly through its interaction with personal smoking.

METHODS

The fifth-decade follow-up of the Tasmanian Longitudinal Health Study cohort, which was first studied in 1968 (n = 8583), included a 2004 postal survey (n = 5729 responses) and subsequent laboratory attendance (n = 1389) for comprehensive lung function testing between 2006 and 2008. Multivariable linear and logistic regression models included sampling weights.

RESULTS

Post-bronchodilator airflow obstruction (less than fifth percentile) was detected for 9.3% (n = 123) of middle-aged offspring. Its association with heavy maternal smoking (>20 cigarettes/day) during childhood was 2.7-fold higher than for those without exposure (95% confidence interval [1.3, 5.7] P = 0.009). Maternal smoking per se approximately doubled the adverse effect of personal smoking on gas transfer factor (z-score -0.46 [-0.6 to -0.3] vs -0.25 [-0.4 to -0.1], P[interaction] = 0.048) and was paradoxically associated with reduced residual volumes for non-smokers.

CONCLUSIONS

Heavy maternal smoking during childhood appears to predispose to spirometrically defined COPD. The interplay between maternal and personal smoking on gas transfer factor suggests that early life exposure increases an individual's susceptibility to adult smoking exposure. These findings provide further evidence to suggest that maternal smoking might be a risk factor for COPD and reinforce the public health message advocating smoking abstinence.

Sex-specific IL-6-associated signaling activation in ozone-induced lung inflammation

Background

Acute ozone (O₃) exposure has known deleterious effects on the respiratory system and has been linked with respiratory disease and infection. Inflammatory lung disease induced by air pollution has demonstrated greater severity and poorer prognosis in women vs. men. Both severe damage to the bronchial-alveolar epithelium and malfunctioning of bronchial-blood barrier have been largely attributed to the pathobiology of O₃-induced inflammatory response, but the associated mechanisms in the male and female lung remain unknown.

Methods

Here, we investigated sex-based differential regulation of lung interleukin-6 (IL-6) and its downstream signaling pathways JAK2/STAT3 and AKT1/NF-κB in response to O₃ exposure in a mouse model. We exposed male and female mice (in different stages of the estrous cycle) to 2 ppm of O₃ or filtered air (FA) for 3 h, and we harvested lung tissue for protein expression analysis by Western blot.

Results

We found significant up-regulation of IL-6 and IL-6R in females and IL-6 in males in response to O₃ vs. FA. Ozone exposure induced a significant increase in STAT3-Y705 phosphorylation in both females and males. Males exposed to O₃ had decreased levels of JAK2, but increased JAK2 (Y1007+Y1008) phosphorylation, while females exposed to O₃ showed significant up-regulation of both proteins. Both NF-κB (p105/p50) and AKT1 protein levels were significantly increased only in females exposed to O₃. In addition, females exposed to O₃ during proestrus displayed increased expression of selected genes when compared to females exposed to O₃ in other estrous cycle stages.

Conclusions

Together, our observations indicate a sex-based and estrous cycle-dependent differential lung inflammatory response to O₃ and involvement of two converging JAK2/STAT3 and AKT1/NF-κB pathways. To our knowledge, this is the first study specifically addressing the impact of the estrous cycle in O₃-associated lung inflammatory pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/s13293-016-0069-7) contains supplementary material, which is available to authorized users.

Effects on pulmonary rehabilitation in patients with COPD or ILD: A retrospective analysis of clinical and functional predictors with particular emphasis on gender

BACKGROUND

The response of patients in a pulmonary rehabilitation (PR) is essentially good. However, not all patients benefit from PR to the same extent. In this analysis we wanted to identify the impact of gender and other factors on PR outcomes in patients with chronic obstructive pulmonary disease (COPD) or interstitial lung disease (ILD).

METHODS

Patients suffering from COPD (n = 1492) or ILD (n = 599), treated during an inpatient PR between 1997 and 2015, were analysed according to the effects of PR on exercise capacity and quality of life with regard to the impact of gender or other predictors by univariate and multivariate analyzes.

RESULTS

In the group of COPD patients, 30% did not achieve the expected physical performance during the 6-min walk test (28% of female and 32% of male patients). However, the non-responders initially have had a higher 6-min walking distance (6-MWD) (p < 0.001) and both male and female showed a significant lower BODE index (p = 0.025) in the multivariate analysis. In the ILD-group, 37% females and 43% males were classified as non-responders with regard to the 6-MWD. Also in this group, the non-responders initially have had a higher 6-MWD (p < 0.001). All other variables (age, BMI, lung function, blood gases, C-reactive Protein, Haemoglobin or rehabilitation duration) had no influence on the outcome.

CONCLUSION

Our study supports the positive effects of PR in COPD and ILD patients. In both groups, patients with the biggest limitations benefit most from PR. However, relevant gender differences or other predictors could not be found.

Impact of individualized care on readmissions after a hospitalization for acute exacerbation of COPD

BACKGROUND

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) increase COPD morbidity and mortality and impose a great burden on health care systems. Early readmission following a hospitalization for AECOPD remains an important clinical problem. We examined how individualized comprehensive care influences readmissions following an index hospital admission for AECOPD.

METHODS

We retrospectively reviewed data of patients admitted for AECOPD to two inner-city teaching hospitals to determine the impact of a comprehensive and individualized care management strategy on readmissions for AECOPD. The control group consisted of 271 patients whose index AECOPD occurred the year before the comprehensive program, and the experimental group consisted of 191 patients who received the comprehensive care. The primary outcome measure was the total number of readmissions in 30- and 90-day postindex hospitalizations. Secondary outcome measures included the length of time between the index admission and first readmission and all-cause mortality.

RESULTS

The two groups were similar in terms of age, sex, forced expiratory volume in 1 second, body mass index (BMI), pack-years, and the number and types of comorbidities. Comprehensive care significantly reduced 90-day readmission rates in females (P=0.0205, corrected for age, BMI, number of comorbidities, substance abuse, and mental illness) but not in males or in the whole group (P>0.05). The average times between index admission and first readmission were not different between the two groups. Post hoc multivariate analysis showed that substance abuse (P<0.01) increased 30- and 90-day readmissions (corrected for age, sex, BMI, number of comorbidities, and mental illness). The 90-day all-cause in-hospital mortality rates were significantly less in the care package group (2.67% versus 7.97%, P=0.0268).

CONCLUSION

Comprehensive individualized care for subjects admitted to hospital for AECOPD did not reduce 30- and 90-day readmission rates but did reduce 90-day total mortality. Interestingly, it reduced 90-day readmission rate in females. We speculate that an individualized care package could impact COPD morbidity and mortality after an acute exacerbation.

Increasing awareness of sex differences in airway diseases

There is growing epidemiologic data demonstrating sex differences with respect to prevalence and progression of airway diseases, including asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF) and non-CF-related bronchiectasis. In asthma, for example, young boys have increased exacerbations and higher morbidity than girls which distinctly reverses after adolescence and into adulthood. In COPD, a disease that was historically considered an illness of men, the number of women dying per year is now greater than in men. Finally, women with CF-related bronchiectasis have a decreased median life expectancy relative to men and a higher risk of respiratory infections despite equal prevalence of the disease. A number of studies now exist demonstrating mechanisms behind these sex differences, including influences of genetic predisposition, sex hormones and comorbidities. The notable sex disparity has potential diagnostic, therapeutic and prognostic implications and for the practicing respiratory or general physician, a familiarity with these distinctions may augment effective management of patients with airway diseases. This review seeks to concisely summarize the data regarding gender-based differences in airway diseases, outline the current understanding of contributing factors and discuss therapeutic implications for clinicians.

Sex-specific features of emphysema among current and former smokers with COPD

Recent studies suggest that males with chronic obstructive pulmonary disease (COPD) have more emphysema than females. It is not known if these differences persist across degrees of COPD severity. Our aim was to identify sex-specific differences in quantitative emphysema within COPD subgroups based on COPD severity.We included non-Hispanic white and African-American subjects from the COPDGene study with at least 10 pack-years of smoking and COPD Global Initiative for Chronic Obstructive Lung Disease (GOLD) spirometry grade II or greater. We examined sex-specific differences in log-transformed emphysema (log per cent low-attenuation area (%LAA)) by GOLD spirometry grade among subjects with early-onset COPD (<55 years old) and advanced emphysema (>25% emphysema).Compared with females, males had higher log %LAA: overall (1.97±1.4 versus 1.69±1.6, β=0.32 (0.04), p=1.34×10(-14)), and among non-Hispanic white (p=8.37×10(-14)) and African-American subjects (p=0.002). Females with early-onset COPD, severe emphysema and GOLD grade IV COPD had similar emphysema as males, but markedly fewer pack-years smoking (early-onset, p=0.01; severe emphysema and GOLD grade IV, p<0.001).This study identifies subsets of female smokers with COPD who are particularly susceptible to parenchymal destruction.

Smoking-Associated Site-Specific Differential Methylation in Buccal Mucosa in the COPDGene Study

DNA methylation is a complex, tissue-specific phenomenon that can reflect both endogenous factors and exogenous exposures. Buccal brushings represent an easily accessible source of DNA, which may be an appropriate surrogate tissue in the study of environmental exposures and chronic respiratory diseases. Buccal brushings were obtained from a subset of current and former smokers from the COPDGene study. Genome-wide DNA methylation data were obtained in the discovery cohort (n = 82) using the Illumina HumanMethylation450K array. Empirical Bayes methods were used to test for differential methylation by current smoking status at 468,219 autosomal CpG sites using linear models adjusted for age, sex, and race. Pyrosequencing was performed in a nonoverlapping replication cohort (n = 130). Current smokers were significantly younger than former smokers in both the discovery and replication cohorts. Seven CpG sites were associated with current smoking at a false discovery rate less than 0.05 in the discovery cohort. Six of the seven significant sites were pyrosequenced in the replication cohort; five CpG sites, including sites annotated to CYP1B1 and PARVA, were replicated. Correlations between cumulative smoke exposure and time since smoking cessation were observed in a subset of the significantly associated CpG sites. A significant correlation between reduced lung function and increased radiographic emphysema with methylation at cg02162897 (CYP1B1) was observed among female subjects. Site-specific methylation of DNA isolated from buccal mucosa is associated with exposure to cigarette smoke, and may provide insights into the mechanisms underlying differential susceptibility toward the development of smoking-related chronic respiratory diseases.

Prevalence and Comorbidities of Chronic Obstructive Pulmonary Disease Among Adults in Kentucky Across Gender and Area Development Districts, 2011

Background: Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality in Kentucky, and precise estimates of the prevalence of this disease and its comorbidities are needed. This study aimed to determine the prevalence of both COPD and its comorbidities and risk differences of COPD comorbidities across Area Development Districts (ADDs) and gender. Methods: The demographic characteristics, prevalence of self- reported COPD and its comorbidities were determined by using data from the 2011 Kentucky Behavioral Risk Factor Survey (KyBRFS). Logistic regression was used to estimate adjusted odds ratios (ORs) for COPD and comorbidities. Results: The overall prevalence of age adjusted COPD was 10.09% (95% confidence interval [CI] 9.99, 10.19), 8.85% for men (95% CI 8.76, 8.93), and 10.78% for women (95% CI 10.67, 10.88). Odds ratios for risk of angina or coronary heart disease (CHD), and arthritis among patients with COPD, by sex and ADDs varied significantly (pooled overall OR=3.43, 95% CI 2.70-4.34, heterogeneity p=0.0001) and (pooled overall OR=2.16, 95% CI 1.75-2.67, heterogeneity p=0.0001), respectively. ORs for risk of depression (pooled OR=2.61, 95% CI 1.78-3.70, heterogeneity p=0.028) and hypertension (pooled OR=1.67, 95% CI 1.16-2.42, heterogeneity p=0. 006) only varied significantly in men. Odds ratios for risk of diabetes was not significant across ADDs and gender (pooled overall OR=2.02, 95% CI 1.61-2.53, heterogeneity p=0.709). Conclusion: Gender differences account for the discrepancy in the risk of comorbidities in patients with COPD across Kentucky's Area Development Districts. This should guide public health officials and physicians to create gender-based prevention interventions.

Sex differences in the expression of lung inflammatory mediators in response to ozone

Sex differences in the incidence of respiratory diseases have been reported. Women are more susceptible to inflammatory lung disease induced by air pollution and show worse adverse pulmonary health outcomes than men. However, the mechanisms underlying these differences remain unknown. In the present study, we hypothesized that sex differences in the expression of lung inflammatory mediators affect sex-specific immune responses to environmental toxicants. We focused on the effects of ground-level ozone, a major air pollutant, in the expression and regulation of lung immunity genes. We exposed adult male and female mice to 2 ppm of ozone or filtered air (control) for 3 h. We compared mRNA levels of 84 inflammatory genes in lungs harvested 4 h postexposure using a PCR array. We also evaluated changes in lung histology and bronchoalveolar lavage fluid cell counts and protein content at 24 and 72 h postexposure. Our results revealed sex differences in lung inflammation triggered by ozone exposure and in the expression of genes involved in acute phase and inflammatory responses. Major sex differences were found in the expression of neutrophil-attracting chemokines (Ccl20, Cxcl5, and Cxcl2), the proinflammatory cytokine interleukin-6, and oxidative stress-related enzymes (Ptgs2, Nos2). In addition, the phosphorylation of STAT3, known to mediate IL-6-related immune responses, was significantly higher in ozone-exposed mice. Together, our observations suggest that a differential regulation of the lung immune response could be implicated in the observed increased susceptibility to adverse health effects from ozone observed in women vs. men.

Sex differences in the intensity and qualitative dimensions of exertional dyspnea in physically active young adults

Understanding sex differences in the qualitative dimensions of exertional dyspnea may provide insight into why women are more affected by this symptom than men. This study explored the evolution of the qualitative dimensions of dyspnea in 70 healthy, young, physically active adults (35 M and 35 F). Participants rated the intensity of their breathing discomfort (Borg 0-10 scale) and selected phrases that best described their breathing from a standardized list (work/effort, unsatisfied inspiration, and unsatisfied expiration) throughout each stage of a symptom-limited incremental-cycle exercise test. Following exercise, participants selected phrases that described their breathing at maximal exercise from a list of 15 standardized phrases. Intensity of breathing discomfort was significantly higher in women for a given ventilation, but differences disappeared when ventilation was expressed as a percentage of maximum voluntary ventilation. The dominant qualitative descriptor in both sexes throughout exercise was increased work/effort of breathing. At peak exercise, women were significantly more likely to select the following phrases: "my breathing feels shallow," "I cannot get enough air in," "I cannot take a deep breath in," and "my breath does not go in all the way." Women adopted a more rapid and shallow breathing pattern and had significantly higher end-inspiratory lung volumes relative to total lung capacity throughout exercise relative to men. These findings suggest that men and women do not differ in their perceived quality of dyspnea during submaximal exercise, but subjective differences appear at maximal exercise and may be related, at least in part, to underlying sex differences in breathing patterns and operating lung volumes during exercise.

Gender differences of chronic obstructive pulmonary disease associated with manifestations on HRCT

BACKGROUND AND AIMS

Patients with chronic obstructive pulmonary disease (COPD) have been shown to have significant gender differences in terms of susceptibility, severity and response to therapy. We hypothesized that this was due to differences in functional and pathologic changes in the airway, which can be revealed by high-resolution computed tomography (HRCT) in addition to pulmonary function test (PFT).

METHODS

A total of 84 patients with COPD were enrolled in the study. Within 1 week of enrollment, a history of each patient's current illness was obtained. PFT and chest HRCT scan were performed.

RESULTS

The patients were classified as phenotype A, E and M based on the chest HRCT presentations. No significant gender differences were found in COPD severity (χ²  = 4.993, P = 0.172). Male patients have more smoking history and smaller average age compared with female patients. Female patients showed a significantly higher FEV₁ /FVC, lower inspiratory capacity and milder residual volume/total lung capacity than that of male patients. Based on the HRCT results, more males were classified as phenotype M, whereas females tended to be phenotype A. Males had a greater grade of low attenuation areas and were more likely to show evidence of emphysema on a HRCT scan than females (χ²  = 15.373, P = 0.001), whereas females had less airway wall thickening than males, although this change had no statistical significance. (χ²  = 0.163, P = 0.922).

CONCLUSION

Gender differences of COPD patients were seen in ages of onset, smoking history, and PFT and HRCT presentations. The use of HRCT imaging indicates that there are significant gender differences in the clinical manifestations of COPD.

Relation between respiratory function tests and life habits of the university students

Among the university students especially in adolescence period, smoking habits and unhealthy lifestyles are major problems in social life. In this study, it is intended to reveal smoking habits and lifestyles of the students from Suleyman Demirel University and to determine the effects of smoking and lifestyles on pulmonary functions.

Materials and methods:

Participants were 94 university students who were getting formal education in the Suleyman Demirel University central campus. Data were analysed by analysis of variance and chi-square tests. For all analysis, p value of <0.05 was considered significant.

Results:

Students’ mean age was 19.9 ± 0.9 years, and of all the students 74 (78.7%) were undergraduate students; remaining 20 (21.3%) were graduate students. Of all the students, 27 (28.7%), which comprised the largest group of the students, were living in state dormitory. Body mass index (BMI) was examined for the study group; according to BMI, body weight was generally within normal limits but 17.39% of girls’ were found to be underweight.

Conclusions:

Respiratory parameters can be affected by many factors. Smoking habit of university students can be prevented, and it is an important point that they have a healthy lifestyle both for their own health and for future generations.

Obesity and extent of emphysema depicted at CT

AIM

To investigate the underlying relationship between obesity and the extent of emphysema depicted at CT.

METHODS AND MATERIALS

A dataset of 477 CT examinations was retrospectively collected from a study of chronic obstructive pulmonary disease (COPD). The low attenuation areas (LAAs; ≤950 HU) of the lungs were identified. The extent of emphysema (denoted as %LAA) was defined as the percentage of LAA divided by the lung volume. The association between log-transformed %LAA and body mass index (BMI) adjusted for age, sex, the forced expiratory volume in one second as percent predicted value (FEV1% predicted), and smoking history (pack years) was assessed using multiple linear regression analysis.

RESULTS

After adjusting for age, gender, smoking history, and FEV1% predicted, BMI was negatively associated with severe emphysema in patients with COPD. Specifically, one unit increase in BMI is associated with a 0.93-fold change (95% CI: 0.91-0.96, p<0.001) in %LAA; the estimated %LAA for males was 1.75 (95% CI: 1.36-2.26, p<0.001) times that of females; per 10% increase in FEV1% predicated is associated with a 0.72-fold change (95% CI: 0.69-0.76, p<0.001) in %LAA.

CONCLUSION

Increasing obesity is negatively associated with severity of emphysema independent of gender, age, and smoking history.

ALAT-2014 Chronic Obstructive Pulmonary Disease (COPD) Clinical Practice Guidelines: questions and answers

ALAT-2014 COPD Clinical Practice Guidelines used clinical questions in PICO format to compile evidence related to risk factors, COPD screening, disease prognosis, treatment and exacerbations. Evidence reveals the existence of risk factors for COPD other than tobacco, as well as gender differences in disease presentation. It shows the benefit of screening in an at-risk population, and the predictive value use of multidimensional prognostic indexes. In stable COPD, similar benefits in dyspnea, pulmonary function and quality of life are achieved with LAMA or LABA long-acting bronchodilators, whereas LAMA is more effective in preventing exacerbations. Dual bronchodilator therapy has more benefits than monotherapy. LAMA and combination LABA/IC are similarly effective, but there is an increased risk of pneumonia with LABA/IC. Data on the efficacy and safety of triple therapy are scarce. Evidence supports influenza vaccination in all patients and anti-pneumococcal vaccination in patients <65years of age and/or with severe airflow limitation. Antibiotic prophylaxis may decrease exacerbation frequency in patients at risk. The use of systemic corticosteroids and antibiotics are justified in exacerbations requiring hospitalization and in some patients managed in an outpatient setting.

Sexually-dimorphic targeting of functionally-related genes in COPD

BACKGROUND

There is growing evidence that many diseases develop, progress, and respond to therapy differently in men and women. This variability may manifest as a result of sex-specific structures in gene regulatory networks that influence how those networks operate. However, there are few methods to identify and characterize differences in network structure, slowing progress in understanding mechanisms driving sexual dimorphism.

RESULTS

Here we apply an integrative network inference method, PANDA (Passing Attributes between Networks for Data Assimilation), to model sex-specific networks in blood and sputum samples from subjects with Chronic Obstructive Pulmonary Disease (COPD). We used a jack-knifing approach to build an ensemble of likely networks for each sex. By adapting statistical methods to compare these network ensembles, we were able to identify strong differential-targeting patterns associated with functionally-related sets of genes, including those involved in mitochondrial function and energy metabolism. Network analysis also identified several potential sex- and disease-specific transcriptional regulators of these pathways.

CONCLUSIONS

Network analysis yielded insight into potential mechanisms driving sexual dimorphism in COPD that were not evident from gene expression analysis alone. We believe our ensemble approach to network analysis provides a principled way to capture sex-specific regulatory relationships and could be applied to identify differences in gene regulatory patterns in a wide variety of diseases and contexts.

Influence of sex on chronic obstructive pulmonary disease risk and treatment outcomes

Chronic obstructive pulmonary disease (COPD), one of the most common chronic diseases and a leading cause of death, has historically been considered a disease of men. However, there has been a rapid increase in the prevalence, morbidity, and mortality of COPD in women over the last two decades. This has largely been attributed to historical increases in tobacco consumption among women. But the influence of sex on COPD is complex and involves several other factors, including differential susceptibility to the effects of tobacco, anatomic, hormonal, and behavioral differences, and differential response to therapy. Interestingly, nonsmokers with COPD are more likely to be women. In addition, women with COPD are more likely to have a chronic bronchitis phenotype, suffer from less cardiovascular comorbidity, have more concomitant depression and osteoporosis, and have a better outcome with acute exacerbations. Women historically have had lower mortality with COPD, but this is changing as well. There are also differences in how men and women respond to different therapies. Despite the changing face of COPD, care providers continue to harbor a sex bias, leading to underdiagnosis and delayed diagnosis of COPD in women. In this review, we present the current knowledge on the influence of sex on COPD risk factors, epidemiology, diagnosis, comorbidities, treatment, and outcomes, and how this knowledge may be applied to improve clinical practices and advance research.

Dietary patterns and pulmonary function in Korean women: findings from the Korea National Health and Nutrition Examination Survey 2007-2011

In the present study, we evaluated the association between dietary patterns and pulmonary functions in Korean women older than 40 years. This study analyzed the data from the Korea National Health and Nutrition Examination Survey IV and V (2007-2010). In total, 7615 women were included in the analysis. Using principal component analysis, two dietary patterns were identified, namely a balanced diet pattern (vegetables, fish, meat, seaweed, and mushrooms) and a refined diet (snacks, bread, milk, dairy products, and fast food). The refined diet pattern was positively associated with energy from fat but negatively associated with vitamin A, β-carotene, niacin, and fiber. After adjusting for potential confounders, the refined diet pattern was negatively associated with levels of predicted forced vital capacity (odds ratio (OR): 0.84, 95% confidence intervals (CIs): 0.70, 0.99) and predicted forced expiratory volume in 1 second (OR: 0.79, 95% CIs: 0.66, 0.93). In conclusion, the refined diet pattern was associated with decreased pulmonary function in Korean women. This information may be useful toward the development of nutritional guidelines for improving pulmonary function in Korean women.

Quantitative Emphysema Distribution in Anatomic and Non-anatomic Lung Regions

PURPOSE

The change of emphysema distribution with increasing COPD severity is not yet assessed. Especially, involvement of the upper aspect of the lower lobe is unknown. The primary aim was to quantitatively determine regional distribution of emphysema in anatomically (lung lobes) and non-anatomically defined lung regions (upper/lower lung halves as well as core and rind regions) in a cohort covering equally all COPD severity stages using CT.

MATERIAL AND METHODS

Basically 100 CT data sets were quantitatively evaluated for regional distribution of emphysema. Emphysema characteristics (emphysema index, mean lung density and 15th percentile of the attenuation values of lung voxels) were compared (t-test) in: upper lobes vs. upper halves, lower lobes vs. lower halves, core vs. rind region.

RESULTS

In patients with ≤ GOLD II, a significantly higher emphysema burden was found in the upper lobes as compared to upper halves. In subjects with GOLD III/IV the differences were not significant for all emphysema characteristics. A high difference between lobes and halves in subjects with ≤ GOLD II was found, in contrast to low difference in higher GOLD stages.

CONCLUSIONS

Lobar segmentation provides improved characterization of cranio-caudal emphysema distribution compared to a non-anatomic approach in subjects up to GOLD stage II.

Ratios of peripheral-to-central airway lumen area and percentage wall area as predictors of severity of chronic obstructive pulmonary disease

OBJECTIVE

The purpose of this study was to assess the ability of the ratios of peripheral-to-central airway lumen area (hereafter referred to as LA) and percentage wall area (hereafter referred to as %WA) to predict the severity of chronic obstructive pulmonary disease (COPD) according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines.

SUBJECTS AND METHODS

We examined 32 patients (27 men and five women; mean age ± SD, 70.0 ± 6.8 years; seven GOLD stage 0 [at risk for COPD], 19 GOLD stage 1-2 [mild to moderate airflow limitation], and six GOLD stage 3-4 [severe to very severe airflow limitation]) using inspiratory CT. Mean LA and %WA were measured for the first (main bronchi), third, and fifth generations of five bronchi in each lobe and the ratios of peripheral to central airways were calculated (third to first, fifth to first, and fifth to third) and statistically compared.

RESULTS

The fifth-generation LA, LA fifth to first, and LA fifth to third significantly decreased and fifth %WA, %WA fifth to first, and %WA fifth to third also increased with progression of GOLD stage (p < 0.05), but central measurements, including first and third generations, did not. There were significant differences between GOLD 0 and GOLD 1-2 for %WA fifth to third and LA fifth to third and between GOLD 0 and GOLD 3-4 for all six parameters (p < 0.05); %WA fifth to third had the best cutoff value of 1.02 (sensitivity, 92%; specificity, 86%) for diagnosis of COPD (GOLD 1-4). The %WA fifth to first of 1.51 (sensitivity, 83%; specificity, 89%) was best for diagnosis of GOLD 3-4.

CONCLUSION

Ratios of peripheral-to-central airway LA and %WA show improved correlation with COPD severity.

The relationships of self-efficacy, physical activity, and paid work to health-related quality of life among patients with chronic obstructive pulmonary disease (COPD)

Purpose

Although chronic obstructive pulmonary disease (COPD) primarily affects the lungs, it is regarded as a systemic disorder associated with comorbidity and physical deterioration, which often results in reduced levels of health-related quality of life (HRQoL). Self-efficacy is an important concept in self-management, which is vital for improving HRQoL in patients with COPD. The purpose of this study was to examine how general self-efficacy, leisure time physical activity, and sociodemographic variables such as employment status are related to the physical and mental health components of HRQoL in patients with COPD.

Patients and methods

In this cross-sectional study, 97 COPD patients (54.6% male, mean age 64.6 years, standard deviation [SD] 9.5) beginning a pulmonary rehabilitation program completed three self-report questionnaires: the short form (SF)-12v2 Health Survey as a measure of HRQoL; the General Self-Efficacy Scale; and a standardized instrument measuring regular leisure time physical activity.

Results

The physical health component median score was 31.3 (interquartile range [IQR] 16.3) and the mental health component median score was 45.9 (IQR 21.5). Two sets of linear regression analyses were performed, one predicting physical health and the other predicting mental health. The first analysis showed that better physical health was directly related to being in paid work (P-value <0.001), but was not significantly related to age, sex, marital status, education, work status, physical activity, or self-efficacy. In the second analysis, better mental health was directly related to living with a partner, being physically active, and having higher self-efficacy (P-value <0.001).

Conclusion

The findings suggest that general self-efficacy has differential relationships to the two dimensions of HRQoL. Our results indicate that general self-efficacy, physical activity, and paid work might be important factors for improving HRQoL of persons with COPD, and should be taken into consideration in pulmonary rehabilitation.

COPD patients with exertional desaturation are at a higher risk of rapid decline in lung function

PURPOSE

A recent study demonstrated that exertional desaturation is a predictor of rapid decline in lung function in patients with chronic obstructive pulmonary disease (COPD); however, the study was limited by its method used to detect exertional desaturation. The main purpose of this study was to explore whether exertional desaturation assessed using nadir oxygen saturation (SpO₂) during the 6-minute walk test (6MWT) can predict rapid lung function decline in patients with COPD.

MATERIALS AND METHODS

A retrospective analysis was performed on 57 patients with moderate to very severe COPD who underwent the 6MWT. Exertional desaturation was defined as a nadir SpO₂ of <90% during the 6MWT. Rapid decline was defined as an annual rate of decline in forced expiratory volume in 1 second (FEV₁)≥50 mL. Patients were divided into rapid decliner (n=26) and non-rapid decliner (n=31) groups.

RESULTS

A statistically significant difference in exertional desaturation was observed between rapid decliners and non-rapid decliners (17 vs. 8, p=0.003). No differences were found between the groups for age, smoking status, BODE index, and FEV₁. Multivariate analysis showed that exertional desaturation was a significant independent predictor of rapid decline in patients with COPD (relative risk, 6.8; 95% CI, 1.8 to 25.4; p=0.004).

CONCLUSION

This study supports that exertional desaturation is a predictor of rapid lung function decline in male patients with COPD.

Lung density on high resolution computer tomography (HRCT) reflects degree of inflammation in smokers

Background

Smokers have increased cell concentration in the lower respiratory tract indicating a chronic inflammatory state, which in some individuals may lead to development of chronic obstructive pulmonary disease (COPD). Computer tomography (CT) imaging provides means of quantifying pulmonary structure and early signs of disease. We investigated whether lung density on high resolution CT differs between smokers and never-smokers and if this were associated to intensity of inflammation.

Methods

Forty smoking volunteers with normal pulmonary function, 40 healthy never-smokers and 40 patients with COPD of GOLD stage I-II, were included. Mean lung attenuation and percentage of pixels in the lung with attenuation between −750 and −900 HU (percentage higher density spectrum (%HDS)) were calculated on inspiratory CT-scans. Markers of systemic inflammation in blood and cell counts in bronchoalveolar lavage (BAL) fluid were recorded.

Results

Lung density expressed as %HDS was increased in smokers (44.0 ± 5.8%) compared to both never-smokers (38.3 ± 5.8%) and patients with COPD (39.1 ± 5.8%), (p < 0.001, for both). Females had denser lungs than males, which was dependent on body height. Cell concentration in BAL were correlated to lung density in smokers (r = 0.50, p < 0.001).

Conclusions

Lung density on CT is associated with cell concentration in BAL in smokers and may mirror an inflammatory response in the lung. Gender difference in lung density is dependent on height. In COPD with emphysema, loss of lung tissue may counterbalance the expected increase in density due to inflammation. The findings may help to interpret high resolution CT in the context of smoking and gender and highlight the heterogeneity of structural changes in COPD.

Cluster analysis in the COPDGene study identifies subtypes of smokers with distinct patterns of airway disease and emphysema

BACKGROUND

There is notable heterogeneity in the clinical presentation of patients with COPD. To characterise this heterogeneity, we sought to identify subgroups of smokers by applying cluster analysis to data from the COPDGene study.

METHODS

We applied a clustering method, k-means, to data from 10 192 smokers in the COPDGene study. After splitting the sample into a training and validation set, we evaluated three sets of input features across a range of k (user-specified number of clusters). Stable solutions were tested for association with four COPD-related measures and five genetic variants previously associated with COPD at genome-wide significance. The results were confirmed in the validation set.

FINDINGS

We identified four clusters that can be characterised as (1) relatively resistant smokers (ie, no/mild obstruction and minimal emphysema despite heavy smoking), (2) mild upper zone emphysema-predominant, (3) airway disease-predominant and (4) severe emphysema. All clusters are strongly associated with COPD-related clinical characteristics, including exacerbations and dyspnoea (p<0.001). We found strong genetic associations between the mild upper zone emphysema group and rs1980057 near HHIP, and between the severe emphysema group and rs8034191 in the chromosome 15q region (p<0.001). All significant associations were replicated at p<0.05 in the validation sample (12/12 associations with clinical measures and 2/2 genetic associations).

INTERPRETATION

Cluster analysis identifies four subgroups of smokers that show robust associations with clinical characteristics of COPD and known COPD-associated genetic variants.

Sex discrepancies in COPD patients and burden of the disease in females: a nationwide study in Greece (Greek Obstructive Lung Disease Epidemiology and health ecoNomics: GOLDEN study)

Background

The prevalence of chronic obstructive pulmonary disease (COPD) in females appears to be increasing. Recent studies have revealed that the percentage of women with COPD in Greece is approximately 12.5%.

Aims

To evaluate the burden of COPD among males and females in Greece through a nationwide cross-sectional survey and to explore sex differences regarding functional characteristics and exacerbation frequency.

Methods

Data collection was completed in a 6-month period. The present study followed a nationwide sampling approach of respiratory medicine physicians. The sampling approach included three steps: 1) estimation of expected incidence and prevalence of COPD cases in each prefecture of Greece and in total; 2) estimation of expected incidence of COPD cases per physician in each prefecture; and 3) creation of a frame of three different sampling zones. Following this sampling, data were provided by 199 respiratory physicians.

Results

The participating physicians provided data from 6,125 COPD patients. Female patients represented 28.7% of the study participants. Female COPD patients were, on average, 5 years younger than male COPD patients. Never smokers accounted for 9.4% within female patients, compared to 2.7% of males (P<0.001). Female patients were characterized by milder forms of the disease. Comorbidities were more prevalent in men, with the exception of gastroesophageal reflux (14.6% versus 17.1% for men and women, respectively, P=0.013). Female COPD patients had a higher expected number of outpatient visits per year (by 8.9%) than males (P<0.001), although hospital admissions did not differ significantly between sexes (P=0.116). Females had fewer absences from work due to COPD per year, by 19.0% (P<0.001), compared to males.

Conclusion

The differences observed between male and female COPD patients provide valuable information which could aid the prevention and management of COPD in Greece.

Pathogenesis of hyperinflation in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a preventable and treatable lung disease characterized by airflow limitation that is not fully reversible. In a significant proportion of patients with COPD, reduced lung elastic recoil combined with expiratory flow limitation leads to lung hyperinflation during the course of the disease. Development of hyperinflation during the course of COPD is insidious. Dynamic hyperinflation is highly prevalent in the advanced stages of COPD, and new evidence suggests that it also occurs in many patients with mild disease, independently of the presence of resting hyperinflation. Hyperinflation is clinically relevant for patients with COPD mainly because it contributes to dyspnea, exercise intolerance, skeletal muscle limitations, morbidity, and reduced physical activity levels associated with the disease. Various pharmacological and nonpharmacological interventions have been shown to reduce hyperinflation and delay the onset of ventilatory limitation in patients with COPD. The aim of this review is to address the more recent literature regarding the pathogenesis, assessment, and management of both static and dynamic lung hyperinflation in patients with COPD. We also address the influence of biological sex and obesity and new developments in our understanding of hyperinflation in patients with mild COPD and its evolution during progression of the disease.

COPD and gender differences: an update

Chronic obstructive lung disease (COPD) is one of the most prevalent health conditions, and a major cause of morbidity and mortality around the globe. Once thought of primarily as a disease of men, COPD is now known to be increasingly prevalent among women. Although increasing tobacco consumption among women during the past several decades might explain some of this increase, the relationship may be more complex, including factors such as differential susceptibility to tobacco, anatomic and hormonal differences, behavioral differences, and differences in response to available therapeutic modalities. Moreover, women with COPD may present differently, may have a different pattern of comorbidities, and may have a better survival after acute exacerbations. Care providers continue to have a gender bias that may affect both diagnosis and treatment. Future work should focus on factors that lead to gender differences in COPD as well as gender-specific treatment strategies.

Association of biomarkers of inflammation and cell adhesion with lung function in the elderly: a population-based study

Background

Low lung function is associated with increased morbidity and mortality. It is therefore of interest to identify biomarkers that are associated with impaired lung function. The aim of the study was to analyse associations of biomarkers and combinations of biomarkers with lung function in an elderly general population.

Methods

Lung function (FEV₁ and FVC) and a panel of 15 inflammatory markers from blood samples were analysed in 888 subjects aged 70 years. Biomarkers included cytokines, chemokines, adhesion molecules, C-reactive protein (CRP) and leukocyte count.

Results

Leukocyte count and CRP were independently associated with FEV₁ after adjustments for other inflammatory markers, sex, BMI, current smoking and pack-years of smoking. In a similar model, leukocyte count and vascular cell adhesion protein 1 (VCAM-1) were the biomarkers that were significantly associated with FVC. Subjects that had both leukocyte count and CRP in the lowest tertile had a FEV₁ that was 9% of predicted higher than subjects with leukocyte count and CRP in the highest tertile (103±16 vs. 94±21% of predicted, p=0.0002) (mean±SD). A difference of 8% of predicted in FVC was found between subjects with leukocyte count and VCAM-1 in the lowest and highest tertiles, respectively (106±18 vs. 98±19% of predicted, p=0.002).

Conclusion

Leucocyte count, CRP and VCAM-1 were found to relate to poorer lung function. A dose related association was found for the combination leukocyte count and CRP towards FEV₁ and leukocyte and VCAM-1 towards FVC. This indicates that combination of two biomarkers yielded more information than assessing them one by one when analysing the association between systemic inflammation and lung function.

Effects of home-based pulmonary rehabilitation with a metronome-guided walking pace in chronic obstructive pulmonary disease

Despite documented efficacy and recommendations, pulmonary rehabilitation (PR) in chronic obstructive pulmonary disease (COPD) has been underutilized. Home-based PR was proposed as an alternative, but there were limited data. The adequate exercise intensity was also a crucial issue. The aim of this study was to investigate the effects of home-based PR with a metronome-guided walking pace on functional exercise capacity and health-related quality of life (HRQOL) in COPD. The subjects participated in a 12-week home-based PR program. Exercise intensity was initially determined by cardiopulmonary exercise test, and was readjusted (the interval of metronome beeps was reset) according to submaximal endurance test. Six-minute walk test, pulmonary function test, cardiopulmonary exercise test, and St. George's Respiratory Questionnaire (SGRQ) were done before and after the 12-week program, and at 6 months after completion of rehabilitation. Thirty-three patients participated in the program. Six-minute walking distance was significantly increased (48.8 m; P = 0.017) and the SGRQ score was also improved (-15; P < 0.001) over the six-month follow-up period after rehabilitation. There were no significant differences in pulmonary function and peak exercise parameters. We developed an effective home-based PR program with a metronome-guided walking pace for COPD patients. This rehabilitation program may improve functional exercise capacity and HRQOL.

Bayesian predictors of very poor health related quality of life and mortality in patients with COPD

Background

Chronic obstructive pulmonary disease (COPD) is associated with increased mortality and poor health-related quality of life (HRQoL) compared with the general population. The objective of this study was to identify clinical characteristics which predict mortality and very poor HRQoL among the COPD population and to develop a Bayesian prediction model.

Methods

The data consisted of 738 patients with COPD who had visited the Pulmonary Clinic of the Helsinki and Turku University Hospitals during 1995–2006. The data set contained 49 potential predictor variables and two outcome variables: survival (dead/alive) and HRQoL measured with a 15D instrument (very poor HRQoL < 0.70 vs. typical HRQoL ≥ 0.70).

In the first phase of model validation we randomly divided the material into a training set (n = 538), and a test set (n = 200). This procedure was repeated ten times in random fashion to obtain independently created training sets and corresponding test sets. Modeling was performed by using the training set, and each model was tested by using the corresponding test set, repeated in each training set. In the second phase the final model was created by using the total material and eighteen most predictive variables. The performance of six logistic regressions approaches were shown for comparison purposes.

Results

In the final model, the following variables were associated with mortality or very poor HRQoL: age at onset, cerebrovascular disease, diabetes, alcohol abuse, cancer, psychiatric disease, body mass index, Forced Expiratory Volume (FEV₁) % of predicted, atrial fibrillation, and prolonged QT time in ECG. The prediction accuracy of the model was 77%, sensitivity 0.30, specificity 0.95, positive predictive value 0.68, negative predictive value 0.78, and area under the ROC curve 0.69. While the sensitivity of the model reminded limited, good specificity, moderate accuracy, comparable or better performance in classification and better performance in variable selection and data usage in comparison to the logistic regression approaches, and positive and negative predictive values indicate that the model has potential in predicting mortality and very poor HRQoL in COPD patients.

Conclusion

We developed a Bayesian prediction model which is potentially useful in predicting mortality and very poor HRQoL in patients with COPD.