Lifestyle Factors and Risk for Symptomatic Gastroesophageal Reflux in Monozygotic Twins

Background & Aims: Lifestyle and genetic factors dominate the etiology of gastroesophageal reflux disease. We investigated associations between lifestyle factors and gastroesophageal reflux (GER) symptoms, with and without controlling for genetic predisposition. Methods: In 1967 and 1973, questionnaires including lifestyle exposures were mailed to twins in the Swedish Twin Registry, and data on GER symptoms were collected by telephone interview during 1998–2002. Two analytic methods were used: external control analysis (4083 twins with GER symptoms and 21,383 controls) and monozygotic co-twin control analysis (869 monozygotic twin pairs discordant for GER symptoms). Results: In the external control analysis, leanness (body mass index [BMI] <20), upper normal weight (BMI 22.5–24.9), overweight (BMI 25–29.9), and obese (BMI ≥30) conferred −19%, 25%, 46%, and 59% increased risk of frequent GER symptoms compared with normal weight (BMI 20–22.4), respectively, among women, whereas no such associations were evident among men. When adjusted for genetic and nongenetic familial factors, these estimates were −28%, 44%, 187%, and 277%, respectively, among men. Frequent smoking rendered a 37% increased risk of frequent GER symptoms among women and 53% among men compared with nonsmokers. Physical activity at work was dose dependently associated with increased risk of frequent GER symptoms, and recreational physical activity decreased this risk. Conclusions: BMI, tobacco smoking, and physical activity at work appear to be risk factors for frequent GER symptoms, whereas recreational physical activity appears to be beneficial. Association between BMI and frequent GER symptoms among men seems to be attenuated by genetic factors.