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Table 1 Characteristics of Doetinchem cohort and Vlagtwedde-Vlaardingen cohort

From: Level and course of FEV1 in relation to polymorphisms in NFE2L2 and KEAP1 in the general population

  Doetinchem cohort
(n = 1,152)
Vlagtwedde-Vlaardingen cohort
(n = 1,390)
Total duration of follow-up (years) 10 25
Number of visits (median) 3 7
The total number of FEV 1 measurements across all visits 3,115 8,159
Follow-up time frame, years 1997–2007 1965–1990
Males, n (%) 541 (47.0) 714 (51.4)
FEV 1 change in ml/year, mean (SD) -26.2 (33.4) -20.8 (22.9)
Last available:   
FEV 1 level in liters, mean (SD) 3.31 (0.80) 2.86 (0.77)
Age in years, median (range) 53.7 (32–76) 52.0 (35–79)
Never smokers, n (%) 372 (32.3) 445 (32.0)
Packyears smoked in ever smokers, median (range) 13.2 (0.004–84.0) 18.9 (0.1–262.2)
  1. FEV1 = Forced Expiratory Volume in 1 second
  2. SD = Standard Deviation