Background: According to the Fletcher-Peto curve, rate of decline in forced expiratory volume in 1-second (FEV1) accelerates as age increases. However, recent studies have not demonstrated that the rate of FEV1 decline accelerates with age among COPD patients. The objective of the study is to evaluate annual rate of FEV1 decline as age increases among COPD patients.
Methods: In this retrospective cohort study, we enrolled COPD patients who were followed up at two tertiary care university hospitals from January 2000 to August 2013. COPD was defined as post-bronchodilator (BD) FEV1/forced vital capacity (FVC) of <0.7. All participants had more than two spirometries, including BD response. Age groups were categorized as follows: below versus above median age or four quartiles.
Results: A total of 518 participants (94.2% male; median age, 67 years; range, 42-90 years) were included. Mean absolute and predictive values of post-BD FEV1 were 1.57±0.62 L and 52.53%±18.29%, respectively. Distribution of Global initiative for Chronic Obstructive Lung Disease groups did not show statistical differences between age groups categorized by two different criteria. After grouping the population by age quartiles, the rate of FEV1 decline was faster among older patients than younger ones whether expressed as absolute value (-10.60±5.57 mL/year, -15.84±6.01 mL/year, -18.63±5.53 mL/year, 32.94±6.01 mL/year, respectively; P=0.048) or predicted value (-0.34%±0.19%/year, -0.53%±0.21%/year, -0.62%±0.19%/year, -1.26%±0.21%/year, respectively, P=0.010).
Conclusion: As suggested conceptually by the Fletcher-Peto curve, annual FEV1 decline among COPD patients is accelerated among older patients than younger ones.
Keywords: age; chronic obstructive lung disease; respiratory function tests.