Figure 2 Relative annual change in FEV₁ (expressed as percentage of baseline) and responsiveness to methacholine in 1991. The scatter plot shows the unadjusted relative annual change in FEV₁ in participants who underwent a bronchial challenge at baseline and spirometric tests at both surveys. The line plot shows the mean annual change in FEV₁ by methacholine slope adjusted for FEV₁ at baseline, sex, height, pack years, exposure to environmental tobacco smoke, area, weight change, and occupation exposure to dust and fumes by smoking status at SAPALDIA 2. The vertical line indicates the PD₂₀ at 2 mg methacholine and thus separates participants with and without bronchial hyperresponsiveness to methacholine.