FIGURE 1.

OR (95% CIs) for the association between serum cysteine and cancer risk relative to the median of the first quartile. We calculated estimates from models with both linear and quadratic terms for serum cysteine with adjustment for age, alcohol intake, BMI, energy intake, cigarettes smoked per day, years of cigarette smoking, education, fruit intake, vegetable intake, gastric adenocarcinomas, and Helicobacter pylori seropositivity. For gastric adenocarcinomas, we observed evidence of a nonlinear association with a P value for the quadratic term of 0.037 and the overall 2-df test for an association of 0.036. For esophageal squamous tumors, we showed no evidence of a deviation from linearity (for the quadratic term: P value= 0.46; for the 2-df test: P = 0.19). For head and neck squamous tumors, we showed no evidence of a deviation from linearity (for the quadratic term: P = 0.19; for the 2-df test: P = 0.34). Q, quartile.