AIM:To study the natural history and prevalence of heartburn at a 10-year interval,and to study the effect of heartburn on various symptoms and activities.METHODS:A population-based postal study was carried out.Questionnaires were mailed to the same age-and gender-stratified random sample of the Icelandic population(aged 18-75 years) in 1996 and again in 2006.Subjects were classified with heartburn if they reported heartburn in the preceding year and/or week,based on the definition of heartburn.RESULTS:Heartburn in the preceding year was reported in 42.8%(1996) and 44.2%(2006) of subjects,with a strong relationship between those who experienced heartburn in both years.Heartburn in the preceding week was diagnosed in 20.8%.There was a significant relationship between heartburn,dyspepsia and irritable bowel syndrome.Individuals with a body mass index(BMI) below or higher than normal weight were more likely to have heartburn.Heartburn caused by food or beverages was reported very often by 20.0% of subjects.CONCLUSION:Heartburn is a common and chronic condition.Subjects with a BMI below or higher than normal weight are more likely to experience heartburn.Heartburn has a great impact on daily activities,sleep and quality of life. AIM: To study the natural history and prevalence of heartburn at a 10-year interval, and to study the effect of heartburn on various symptoms and activities. METHHODS: A population-based postal study was carried out. Questionednaires were mailed to the same age -and gender-stratified random sample of the Icelandic population (aged 18-75 years) in 1996 and again in 2006. Subjects were classified with heartburn if they reported heartburn in the previous year and / or week, based on the definition of heartburn. RESULTS: Heartburn in the preceding year was reported in 42.8% (1996) and 44.2% (2006) of subjects, with a strong relationship between those who experienced heartburn in both years. Heartburn in the preceding week was diagnosed in 20.8%. There was a significant relationship between heartburn, dyspepsia and irritable bowel syndrome. Individuals with a body mass index (BMI) below or higher than normal weight were more likely to have heartburn. Heartburn caused by food or beverages was reported very often by 20.0% of subjects.CONCLUSION: Heartburn is a common and chronic condition.Subjects with a BMI below or higher than normal weight are more likely to experience heartburn. Heartburn has a great impact on daily activities, sleep and quality of life.