Almost all persons are infected with HP during childhood. Infection with the bacteria in adulthood is rare. Only few persons spontaneously turn HP-negative. From OPED we will know which individuals who have been prescribed HP-eradication treatment. Thus the participants in the control group, who are HP-positive at 12-yr follow-up, have had the infection the whole period. Provided they have not received HP-eradication treatment, those who are tested HP-negative have been so the whole period.