Objective: To compare the lifetime pattern of physical activity (PA) in chronic obstructive pulmonary disease (COPD) patients and sedentary healthy subjects (SHS) using a PA questionnaire with a lifetime period of recall (Quantification de l'Activite Physique [QUANTAP] system), and to compare the pattern of PA reduction in COPD patients with the onset of breathlessness and other relevant clinical events in this disease (diagnosis, first rehabilitation, onset of smoking). Design: Cross-sectional comparative study. Settings: Outpatient university hospital and inpatient pulmonary rehabilitation center. Participants: COPD patients (n=129; mean age +/- SD, 61 +/- 10y; forced expiratory volume in Is, 57 +/- 23%) and SHS (n=29; mean age +/- SD, 61 +/- 5y; <150min.wk(-1) of moderate-vigorous PA). Interventions: Not applicable. Main Outcome Measures: Lifetime PA was compared in COPD patients and SHS using the QUANTAP system. The patients with COPD and SHS underwent pulmonary function, exercise, and quadriceps endurance testing. The current PA level was assessed with a triaxial accelerometer and the Voorrips questionnaire. The age at the onset of breathlessness was also recorded. Results: Accelerometry showed no significant difference between patients and SHS (in vector magnitude units, 136 +/- 56 vs 135 +/- 47; P=.95). Within the past 15 years, the cumulated PA level was not different for each 5-year period. Then, from the period of 16 to 40 years ago, it was systematically higher in patients compared with SHS (in metabolic equivalent/y(-1); median [interquartile range], 6973 [5400-12,207] vs 4248 [3545-5919]; P<.05). The COPD patients reduced their PA earlier than the SHS (45y vs 55y; P<.01), and the PA was dropped before the onset of breathlessness (45y vs 49y; P<.001). Conclusions: The observation of an early PA reduction, preceding the onset of breathlessness, suggests the implication of prior pathologic mechanisms in the PA reduction of COPD patients.