Fig. 2

Observational associations of serum urate with FEV₁ and lung cancer incidence in regular smokers by sex adjusted for age, calendar year, ethnicity (first 40 principal components), packyears of smoking, height and recruitment centre (Model 1), additionally for weight (Model 2) and waist circumference, alcohol consumption, exposure to smoke at home, social deprivation, air pollution levels (nitrogen dioxide), and intake of antioxidant supplements (Model 3). Non-linear relationships were captured using restricted cubic spline transformation with three knots placed at the 10th, 50th and 90th percentiles of urate level