Table 1.
Association between Symptoms and Lung Function Decline among Individuals at GOLD Stage 0
| Study | Prevalence of Symptoms | Outcome |
|---|---|---|
| Copenhagen City Heart (8, 25) | Baseline prevalence of CB: 7.1% of men and 4.8% of women | • After 5 and 15 yr, COPD developed in 13.2% and 20.5% of smokers at GOLD stage 0 at enrollment, respectively |
| • At 5 and 15 yr, respectively, 11.6% and 18.5% of smokers without respiratory symptoms also were at GOLD stage 1 or worse | ||
| • Symptoms at GOLD stage 0 were associated with excess loss of 19 ml/yr in addition to the FEV1 decline seen in unobstructed smokers without these symptoms | ||
| ECRHS (26, 27) | At baseline, 9.2% subjects reported chronic cough and phlegm | • The incidence of COPD in subjects who confirmed the presence of chronic cough and phlegm at the end of the follow-up (9.4 cases of 1,000/yr; 95% CI, 5.6–15.9) was fourfold higher than the incidence in subjects who had never reported these symptoms (2.3 cases of 1,000/yr; 95% CI, 1.9–2.9) (incidence rate ratio, 1.85; 95% CI, 1.17–2.93) |
| • The incidence of COPD in subjects with persistent dyspnea (3.2 cases of 1,000/yr; 95% CI, 1.6–6.5) was not significantly different from the incidence of COPD in subjects who had never reported this symptom (2.4 cases of 1,000/yr; 95% CI, 1.9–3.0) | ||
| Northern Swedish cohort (17) | At baseline, 41.9% of subjects reported chronic productive cough | • The 10-yr cumulative incidence of COPD was 13.5%. The cumulative incidence of COPD among persistent smokers was close to three times the incidence among persistent nonsmokers (24.5% vs. 9.4%, respectively) |
| • When analyzed as an entire cohort, every type of symptom was associated with increased risk for COPD | ||
| • However, when men and women were analyzed separately, cough, sputum production, and chronic productive cough were significantly associated with incident COPD in women, whereas dyspnea and wheeze were significantly associated with incident COPD in men | ||
| SAPALDIA cohort (22) | At baseline, among those without airflow obstruction, 8.1% of subjects reported CB symptoms | • CB was associated with incident COPD as defined by prebronchodilator spirometric results (rate ratio, 1.23; 95% CI, 1.00–1.51) |
| UK MRC cohort (19) | Among smokers, CB prevalence escalated between the ages of 36 and 43 yr from 7.6% to 13.0% | • Symptoms were associated with a higher risk of subsequent airflow limitation (ORs, 3.70 and 4.11, respectively) |
| • The longer CB was present across three occasions (ages 43, 53, and 60–64 yr), the greater the concurrent FEV1 decline, corresponding to an additional decrement of 3.6 ml/yr per occasion that CB was present (P = 0.005) | ||
| TESAOD (20) | CB present in 6.9% (majority current or former smokers) | • Incident airflow obstruction among those with CB, 1.37 (P = 0.07) |
| • Mortality risk was higher among smokers (adjHR, 1.50) than nonsmokers (0.80) and among subjects <50 yr of age (2.22) vs. >50 yr of age (0.96) | ||
| ARIC (23) | The prevalence of GOLD stage 0 was 14.5% in a population-based cohort based on prebronchodilator spirometric results and any respiratory symptom, including cough, phlegm, wheeze, and breathlessness. Overall, 20% of those with normal spirometric results reported symptoms | • HR, 1.6 for death among participants at GOLD stage 0 as compared with unobstructed individuals without symptoms |
| Oslo Norway cohort (24) | The prevalence of GOLD stage 0 was 8.1% in a population-based cohort of men in Oslo, Norway. Overall, 9.7% of those without airflow obstruction demonstrated respiratory symptoms | • Subjects at GOLD stage 0 using a modified definition (prebronchodilator spirometric results and any respiratory symptom, including dyspnea and phlegm) had increased risk for mortality (HR, 1.35) |
| CARDIA cohort (18) | The prevalence of any respiratory symptom in a population-based cohort at baseline and Year 2 was 43.9% | • Respiratory symptoms, including cough or phlegm, episodes of bronchitis, wheeze, shortness of breath, and chest illness were assessed at baseline and Year 2 and examined in conjunction with lung function from Year 5 to Year 30 |
| • Report of any symptom was associated with a 2.71-ml/yr excess decline in FEV1 (P < 0.001) and a 2.18-ml/yr excess decline in FVC (P < 0.001) as well as a 1.63 OR for development of incident obstruction | ||
| • Cough-related symptoms in particular were associated with a 1.56 OR for development of visually assessed emphysema on Year 25 CT scans |
Definition of abbreviations: adjHR = adjusted HR; ARIC = Atherosclerosis Risk in Communities; CARDIA = Coronary Artery Risk Development in Young Adults; CB = chronic bronchitis; CI = confidence interval; COPD = chronic obstructive pulmonary disease; CT = computed tomography; ECRHS = European Community Respiratory Health Survey; GOLD = Global Initiative for Chronic Obstructive Lung Disease; HR = hazard ratio; MRC = Medical Research Council; OR = odds ratio; SAPALDIA = Swiss Study on Air Pollution and Lung Disease in Adults; TESAOD = Tucson Epidemiological Study of Airway Obstructive Disease; UK = United Kingdom.