Trajectory of Preserved Ratio Impaired Spirometry: Natural History and Long-Term Prognosis

Rationale: Natural history of Preserved Ratio Impaired Spirometry (PRISm), often defined as FEV1/FVC≥lower limit of normal and FEV1<80% of predicted value, is not well-described. Objective: To investigate natural history and long-term prognosis of PRISm trajectories: persistent PRISm trajectory (individuals with PRISm both as young and as middle-aged); normal-to-PRISm trajectory (individuals developing PRISm from normal spirometry in young adulthood); and PRISm-to-normal trajectory (individuals recovering from PRISm in young adulthood by normalizing spirometry while middle-aged). Methods: We followed 1160 individuals aged 20-40 years from the Copenhagen City Heart Study from 1976-83 until 2001-03 to determine their lung function trajectory: 72 had persistent PRISm trajectory, 76 normal-to-PRISm trajectory, 155 PRISm-to-normal trajectory, and 857 had normal trajectory. From 2001-03 until 2018, we determined risk of cardiopulmonary disease and death. Measurements and Main Results: We recorded 198 admissions for heart disease, 143 for pneumonia, and 64 for COPD, and 171 deaths. Compared to individuals with normal trajectory, hazards ratios for individuals with persistent PRISm trajectory were 1.55 (95% CI, 0.91—2.65) for heart disease admission, 2.86 (1.70—4.83) for pneumonia admission, 6.57 (3.41—12.66) for COPD admission, and 3.68 (2.38—5.68) for all-cause mortality. Corresponding hazards ratios for individuals with normal-to-PRISm trajectory were 1.91 (1.24—2.95), 2.74 (1.70—4.42), 6.03 (3.41—10.64), and 2.96 (1.94—4.51), respectively. Prognosis of individuals with PRISm-to-normal trajectory did not differ from those with normal trajectory. Conclusions: PRISm in middle-aged individuals is associated with increased risk of cardiopulmonary disease and all-cause mortality, but individuals who recover from PRISm during their adult life are no longer at increased risk.