Determinants of respiratory symptom development in patients with chronic airflow obstruction

Background: This study was undertaken to identify the determinants of respiratory symptom development in patients with chronic airflow obstruction (CAO). Methods: Categories of symptomatic and asymptomatic CAO were defined using questionnaire responses and spirometric results. We analyzed data obtained as part of the second South Korean National Health and Nutrition Examination Survey (Korean NHANES II). Results: Among 187 patients with CAO, 69 had no respiratory symptoms. CAO patients with symptoms were significantly older than those without symptoms (P = 0.026), and hypertension was more common among symptomatic CAO patients than among asymptomatic CAO patients (P = 0.005). According to questionnaire responses, symptomatic CAO patients had more difficulty in walking or lifting (P < 0.001), required more help with personal care (P = 0.01), and had poorer general health than asymptomatic CAO patients (P = 0.008). Symptomatic CAO patients had higher fasting blood glucose levels than asymptomatic CAO patients (P = 0.028). Symptomatic CAO patients had significantly lower forced expiratory volume in 1 s (FEV₁) (P = 0.001), forced vital capacity (FVC) (P = 0.008), and a ratio of FEV₁/FVC than asymptomatic CAO patients (P < 0.001). Statistically significant predictors of symptom development were as follows: age (odds ratio (OR) 1.04, P = 0.028), hypertension (OR 4.41, P = 0.008), fasting blood glucose (OR 1.02, P = 0.034), FEV₁ (OR 0.07, P = 0.002), FVC (OR 0.08, P = 0.009), FEV₁/FVC (OR 0.00, P = 0.001). Multiple logistic regression analyses revealed two independent factors associated with symptom development: FEV₁/FVC (OR 0.001, P = 0.002) and hypertension (OR 5.95, P = 0.005). Conclusions: In CAO, respiratory symptom development is significantly associated with low FEV₁/FVC and the presence of hypertension.