Summary
Background
Chronic obstructive pulmonary disease (COPD) and cardiovascular diseases (CVD) share risk factors and impair each other’s prognosis.
Aims
To assess the prevalence of airflow limitation (AL) compatible with COPD in a population at cardiovascular risk and to identify determinants of AL.
Methods
All consecutive patients referred to the cardiovascular prevention unit of a university hospital in 2009 were studied in a cross-sectional analysis. Patients answered questionnaires on socioeconomic status, medical history and lifestyle, and underwent extensive physical examinations, biological measures and spirometry testing. AL was defined as FEV1/FVC < 0.70, without any history of asthma. Determinants of AL were assessed using logistic regression.
Results
The sample comprised 493 participants (mean age 57.4 ± 11.1 years); 60% were men, 18% were current smokers, 42% were ex-smokers and 10% of patients had a history of CVD. Ten-year risk of coronary heart disease (CHD) according to the Framingham equation was intermediate (10–20%) for 25% of patients and high (> 20%) for 10%. Prevalence of AL was 5.9% (95% confidence interval [CI] 4.0–8.3%) in the whole population and 4.3% (2.6–6.6%) among subjects in primary cardiovascular prevention. AL was independently associated with CVD (adjusted odds ratio 4.18, 95% CI 1.72–10.15; P = 0.002) but not with Framingham CHD risk. More than 80% of patients screened with AL had not been diagnosed previously and more than one in two patients was asymptomatic.
Conclusion
Patients with CVD are at increased risk of AL and thus should benefit from AL screening as they are frequently asymptomatic.
Résumé
Contexte
La broncho-pneumopathie chronique ostructive (BPCO) et les maladies cardiovasculaires (CV) présentent des facteurs de risques communs et leur association chez un même patient grève le pronostic.
L’objectif
A été d’évaluer la prévalence des troubles ventilatoires obstructifs (TVO) dans une population à risque CV et d’analyser les déterminants de l’obstruction bronchique.
Méthodes
Notre étude est basée sur les patients adressés au centre de détection et de prévention de l’athérosclérose du CHU de Toulouse en 2009. Les participants ont répondu à un questionnaire évaluant le niveau socioéconomique, les antécédents médicaux et le style de vie. Ils ont bénéficié d’un examen clinique et d’une spirométrie. Un TVO était diagnostiqué si VEMS/CV était inférieur à 0,70 sans antécédent d’asthme. Les déterminants du TVO ont été évalués par régression logistique.
Résultats
L’échantillon comprend 493 participants (âge moyen : 57,4 ± 11,1 ans), dont 60 % d’hommes, 18 % des fumeurs actuels, 42 % d’anciens fumeurs et 10 % de sujets atteints de maladies CV. Le risque de maladie coronarienne à dix ans selon l’équation de Framingham était intermédiaire (10–20 %) pour 25 % des sujets et élevé (> 20 %) pour 10 %. La prévalence des TVO était de 5,9 % [IC95 % : 4,0–8,3 %] (4,3 % [IC95 % : 2,6 %–6,6 %] chez les sujets en prévention CV primaire). Le TVO était indépendamment associé aux maladies CV (OR ajusté = 4,18 [1,72–10,15] ; p = 0,002) mais pas au score de Framingham. Plus de 80 % des patients dépistés avec un TVO n’en avaient pas connaissance et un patient sur deux était asymptomatique.
Conclusion
Les patients atteints de maladies CV ont un risque accru de BPCO qui est souvent asymptomatique. Ils devraient donc bénéficier d’un dépistage spirométrique.
Introduction
COPD affects approximately 7.5% of the adult population. By 2020, COPD is expected to be the third most common cause of death and the fifth most common cause of disability in the world . Paradoxically, this disease is widely under-diagnosed , in part because symptoms appear progressively and become obvious only when lung function is already significantly impaired . Besides, COPD is strongly associated with CVD and, among subjects with CVD, the coexistence of COPD is associated with a raised morbidity including more frequent hospitalizations and worsening of symptoms . In addition, cardiovascular deaths account for a significant part of the mortality in COPD patients.
COPD prevalence has been estimated in several studies among patients with CVD , but remains unknown in asymptomatic subjects at cardiovascular risk for whom the combination with COPD may worsen prognosis . Such a situation should be avoided today as COPD is now considered as a preventable and treatable disease .
The aim of this study was to assess the prevalence of AL in a population at cardiovascular risk and to identify determinants of AL in this population.
Methods
Patients
This report is based on a cross-sectional study comprising 519 consecutive subjects referred to a preventive cardiology unit in a French university hospital between January 2009 and January 2010. Patients were either self-referred or referred by their primary care physician or cardiologist for cardiovascular risk assessment, management of risk factors and routine ambulatory screening for CVD. All of the patients were invited to participate in the study; 502 (97%) accepted. The study was approved by the appropriate ethics committee, in accordance with French law ( Comité de protection des personnes Sud-Ouest et Outre-Mer II , number 2-08-25) and all participants signed an informed consent form attesting they had received information about the study and agreed to participate.
Data collection
An extensive questionnaire, derived from the questionnaire used in the French MONICA (monitoring trends and determinants in CVD) population surveys carried out in the same region, was administered to each participant by a trained and certified medical staff member. Data concerning socioeconomic status, personal and family medical history (including family history of premature myocardial infarction, i.e. before 55 years for the father or 65 years for the mother), drug intake, cardiovascular risk factors, pulmonary symptoms (cough, sputum, dyspnoea), lifestyle and quality of life were recorded. Educational level was assessed by the level of graduation or school dropout. Smoking status was described as never smoking (0 pack-years), past smoking (smoking cessation ≥ 1 year before inclusion in the study) or current smoking (estimated in pack-years). All subjects underwent a physical examination, blood sample collection, electrocardiography, exercise test and spirometry test. A maximal exercise test was defined as a peak heart rate ≥ 85% of the maximal predicted heart rate for a given age . The exercise test was stopped when the participant was unable to continue or in the case of electrocardiographic or blood pressure abnormalities. Height, weight and arterial blood pressure (mean of two measurements performed with an automatic sphygmomanometer in a sitting position after ≥ 5 min of rest) were measured according to standardized protocols by the medical staff. Body mass index was calculated as weight divided by height squared (kg/m 2 ). Dyspnoea was quantified according to the modified Medical Research Council (MRC) scale . Symptoms of chronic bronchitis were assessed using questions derived from the European Community Respiratory Health Survey . Quality of life was measured by the EuroQol 5D scale .
Blood samples were taken after ≥ 10 h of overnight fast. LDL-C was determined by the Friedewald formula . Diabetes was assessed for people with fasting blood glucose ≥ 7 mmol/L (126 mg/dL) or under hypoglycaemic drug treatment. The 10-year risk of CHD (hard event, i.e. myocardial infarction, coronary insufficiency or CHD death) was estimated with the Framingham equation (charts using LDL-C categories) in subjects without CVD (i.e., ischaemic heart disease, history of cerebrovascular disease or atherosclerosis in other arteries such as aorta, renal or lower limb arteries) .
Spirometry
Spirometry was conducted according to ATS/ERS guidelines by means of a portable spirometer (MINISPIR, MIR Medical, Rome, Italy). All spirometric measurements were reviewed individually and graded for quality by an experienced senior pulmonologist (R.E.).
AL compatible with COPD was defined according to the Global initiative for Obstructive Lung Disease (GOLD) guidelines , when forced expiratory volume in 1 s (FEV 1 ) divided by forced vital capacity (FVC) was < 0.70, without any history of asthma. The severity of AL was staged according to the GOLD guidelines as mild (stage I), moderate (stage II), severe (stage III) or very severe (stage IV), respectively, for percent predicted FEV 1 ≥ 80%, 50% ≤ FEV1 < 80%, 30% ≤ FEV1 < 50%, and FEV1 < 30% (or FEV1 < 50% plus chronic respiratory failure), respectively. Because our population was at cardiovascular risk and because a maximal stress test was included in the check-up (performed on a single day) , postbronchodilator reversibility to beta-2 agonists could not be tested.
Statistical analysis
The statistical analysis was performed with Stata statistical software (version 9.2, STATA Corporation, College station, TX, USA). Prevalence of AL is given with 95% confidence interval (CI). In bivariate analysis, qualitative variables were compared with the χ 2 -test (or bilateral Fisher’s exact test, when necessary). Student’s t -test (or the Mann-Whitney’s test when the distribution of continuous variables was skewed or the hypothesis of homoscedasticity was not respected) was used to compare quantitative data according to categories of qualitative variables. As bivariate analyses were performed only to screen variables that should be introduced in multivariable models, no adjustment for multiple comparisons was performed. Independent determinants of AL were assessed with logistic regression. Variables associated with AL in bivariate analysis ( P < 0.20) were introduced in the multivariable model. A backward procedure was applied to assess variables that were significantly and independently associated with AL ( P < 0.05). Age and smoking status were kept in the model despite a P -value > 0.05 as they are well known risk factors for AL.
Results
Population sample
Overall, 502 of the 519 eligible subjects (97%) agreed to participate. Nine patients with FEV 1 /FVC < 0.70 and a history of asthma were excluded from the analysis, as asthma and COPD could not be differentiated in these patients due to the lack of reversibility testing. Table 1 describes the 493 patients at cardiovascular risk enrolled in the study. Mean age was 57.4 ± 11.1 years. Of the study population, 60% were men, 18% were current smokers, 42% were ex-smokers and 10% had CVD. The 10-year risk of a CHD event (calculated only in patients without CVD), according to the Framingham equation (LDL-C chart) , was intermediate (between 10 and 20%) for 25% of patients and high (> 20%) for 10% of the sample.
| Patients at cardiovascular risk ( n = 493) | |
|---|---|
| Age (years) | 57.4 ± 11.1 |
| Men | 294 (60) |
| Educational level ≥ high school completion | 285 (58) |
| Smoking status | |
| Never | 200 (41) |
| Past | 206 (42) |
| Current | 87 (18) |
| Diabetes | 37 (8) |
| Antihypertensive drug treatment | 126 (26) |
| Lipid-lowering drug | 216 (44) |
| Body mass index (kg/m 2 ) | 26 ± 4.6 |
| C-reactive protein (mg/L) | 2.9 ± 4.6 |
| Family history of premature myocardial infarction a | 29 (6) |
| Framingham hard CHD risk b | |
| < 10% | 256 (54) |
| 10–20% | 120 (25) |
| > 20% | 49 (10) |
| History of cardiovascular disease c | 47 (10) |
| History of COPD d | 12 (2) |
a Family history of premature myocardial infarction, i.e. before 55 years old for the father or 65 for the mother.
b 10-year risk of hard coronary heart disease event according to the Framingham equation (chart using LDL-cholesterol categories) in subjects without any history of cardiovascular disease.
c Ischaemic heart disease, history of cerebrovascular disease, atherosclerosis in other arteries such as
Prevalence of airflow limitation
A total of 29 patients exhibited AL. Fig. 1 shows the prevalence of AL according to the GOLD classification and the prevalence of AL or reported COPD. The overall prevalence of FEV 1 /FVC < 0.70 (AL) was 5.9% (95% CI 4.0–8.3%). Twenty-three patients (79.5%) presented in GOLD stage I, 17% ( n = 5) in GOLD stage II and 3.5% ( n = 1) in GOLD stage III. None of the AL patients reached stage IV. The prevalence of FEV 1 /FVC < 0.70 without previously known COPD (screened AL) was 5.1% (95% CI 3.3–7.4%) (i.e., 86% [ n = 25] of AL patients had not been diagnosed previously). The prevalence of FEV 1 /FVC < 0.70 or reported COPD (with FEV 1 /FVC ≥ 0.70) was 7.5% (95% CI 5.3–10.2%) (eight patients reported COPD but exhibited a normal FEV 1 /FVC ratio).
