Harmonization of Respiratory Data From Nine US Population-Based Cohorts: The NHLBI Pooled Cohorts Study

Abstract

Chronic lower respiratory diseases (CLRD) are the fourth leading cause-of-death in the US. To support investigations into CLRD risk determinants and new approaches to primary prevention, we aimed to harmonize and pool respiratory data from US general population-based cohorts. Data were obtained from prospective cohorts that performed pre-bronchodilator spirometry, which was harmonized following 2005 ATS/ERS standards. In cohorts conducting follow-up for non-cardiovascular events, CLRD events were defined as hospitalizations/deaths adjudicated as CLRD-related or assigned relevant administrative codes. Coding and variable names were applied uniformly. The pooled sample included 65,251 adults in nine cohorts followed-up for CLRD-related mortality over 653,380 person-years from 1983-2016. Average baseline age was 52 years; 56% were female; 49% were never-smokers; and racial/ethnic composition was 44% White, 22% Black, 28% Hispanic/Latino, and 5% American-Indians. Over 96% had complete data on smoking, clinical CLRD diagnoses, and dyspnea. After excluding invalid spirometry exams (13%), there were 105,696 valid exams (median 2 per participant). Of 29,351 participants followed-up for CLRD hospitalizations, median follow-up was 14 years; only 5% were lost-to-follow-up at 10 years. Hence, the NHLBI Pooled Cohorts Study provides a harmonization standard applied to a large, US population-based sample that may be used to advance epidemiologic research on CLRD.