Limitations of this study
The study was limited to patients who underwent gastroscopy with biopsy for clinical indications. This group may differ from the general population in several ways, and our findings cannot be readily generalised to non-patients (or healthy people who undergo screening). On the other hand, only patients presently undergo gastroscopy, and in the study we aimed to create a basis for predictions for this particular group. The fact that virtually all patients who undergo biopsy in Sweden were included in the cohort vouches for reasonable external validity of this group. The standardised incidence ratio for gastric cancer among people with normal mucosa was 1.0, which contradicts a strong link between lifestyle or genetic determinants for gastroscopic examinations and future risk of gastric cancer.