Relationships between respiratory symptoms and FEV₁ in men and women with normal lung function: The Korean health and genome study

Although the prevalence of chronic obstructive pulmonary disease (COPD) and its relationship with respiratory symptoms are well documented, few studies have focused on individuals with normal lung function, particularly in developed regions of Asia. The purpose of this report is to examine the relationship between respiratory symptoms and FEV₁ in a population-based sample of Korean men and women with normal lung function. Subjects comprised 7518 individuals aged 40-69 years without airflow obstruction based on spirometric testing and in the absence of a medical history of pulmonary disease. Respiratory symptoms included chronic cough, chronic phlegm, wheezing, and shortness of breath. In men, the age-adjusted mean FEV₁ was lower by 165 ml in smokers and 133 ml in nonsmokers in the presence versus the absence of wheezing (p < 0.05). While walking at a usual pace, FEV₁ in smoking men was 210 ml lower in the presence versus the absence of shortness of breath (p < 0.05). Among nonsmoking men, overall shortness of breath and shortness of breath while walking uphill were associated with a lower FEV ₁ by 56 and 80 ml, respectively) versus those who reported having no shortness of breath (p < 0.05). Respiratory symptoms were unrelated to FEV₁ in women smokers, although only 3.5% smoked cigarettes. In nonsmoking women, FEV₁ was lower by an average of 89 ml in the presence versus the absence of wheezing (p < 0.001). Nonsmoking women also had a lower FEV₁ in the presence of shortness of breath (overall, while at rest, and while walking uphill or at a usual pace, p < 0.001). Our findings suggest that respiratory symptoms are associated with a lower FEV ₁ in men and nonsmoking women with normal lung function. Whether respiratory symptoms can be used to identify individuals at risk for developing COPD needs further study.