Figure 2. Quartiles of H. pylori antibody titer and seroprevalence according to history of eradication treatment for H. pylori among ever-infected subjects in the JPHC–NEXT Study. Subjects were classified according to self-reported treatment history for H. pylori as follows: none: untreated; treated less than 1 year: <1Y; treated 1 to 5 years ago: 1–5Y; and treated 6 or more years ago: 6Y+. A) Spline-smoothed lines connecting the 25^th, 50^th, and 75^th percentiles of antibody titers in each group, respectively. B) Spline-smoothed lines for seroprevalence of H. pylori according to treatment history. H. pylori antibody titers of <3 U/mL, ≥3 to <10 U/mL, and ≥10 U/mL were defined as low-negative, high-negative and positive, respectively.