title: Physical activity, obesity and gastroesophageal reflux disease in the general population.
abstract: OBJECTIVE
  To clarify the association between physical activity and gastroesophageal reflux disease (GERD) in non-obese and obese people.
  
  
  METHODS
  A Swedish population-based cross-sectional survey was conducted. Participants aged 40-79 years were randomly selected from the Swedish Registry of the Total Population. Data on physical activity, GERD, body mass index (BMI) and the covariates age, gender, comorbidity, education, sleeping problems, and tobacco smoking were obtained using validated questionnaires. GERD was self-reported and defined as heartburn or regurgitation at least once weekly, and having at least moderate problems from such symptoms. Frequency of physical activity was categorized into three groups: (1) "high" (several times/week); (2) "intermediate" (approximately once weekly); and (3) "low" (1-3 times/mo or less). Analyses were stratified for participants with "normal weight" (BMI < 25 kg/m²), "overweight" (BMI 25 to ≤ 30 kg/m²) and "obese" (BMI > 30 kg/m²). Multivariate logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (CIs), adjusted for potential confounding by covariates.
  
  
  RESULTS
  Of 6969 eligible and randomly selected individuals, 4910 (70.5%) participated. High frequency of physical activity was reported by 2463 (50%) participants, GERD was identified in 472 (10%) participants, and obesity was found in 680 (14%). There were 226 (5%) individuals with missing information about BMI. Normal weight, overweight and obese participants were similar regarding distribution of gender and tobacco smoking status, while obese participants were on average slightly older, had fewer years of education, more comorbidity, slightly more sleeping problems, lower frequency of physical activity, and higher occurrence of GERD. Among the 2146 normal-weight participants, crude point estimates indicated a decreased risk of GERD among individuals with high frequency of physical activity (OR: 0.59, 95% CI: 0.39-0.89), compared to low frequency of physical activity. However, after adjustment for potential confounding factors, neither intermediate (OR: 1.30, 95% CI: 0.75-2.26) nor high (OR: 0.99, 95% CI: 0.62-1.60) frequency of physical activity was followed by decreased risk of GERD. Sleeping problems and high comorbidity were identified as potential confounders. Among the 1859 overweight participants, crude point estimates indicated no increased or decreased risk of GERD among individuals with intermediate or high frequency of physical activity, compared to low frequency. After adjustment for confounding, neither intermediate (OR: 0.75, 95% CI: 0.46-1.22) nor high frequency of physical activity were followed by increased or decreased risk of GERD compared to low frequency among nonobese participants. Sleeping problems and high comorbidity were identified as potential confounders for overweight participants. In obese individuals, crude ORs were similar to the adjusted ORs and no particular confounding factors were identified. Intermediate frequency of physical activity was associated with a decreased occurrence of GERD compared to low frequency of physical activity (adjusted OR: 0.41, 95% CI: 0.22-0.77).
  
  
  CONCLUSIONS
  Intermediate frequency of physical activity might decrease the risk of GERD among obese individuals, while no influence of physical activity on GERD was found in non-obese people.
authors.affiliation: Unit of Upper Gastrointestinal Research, Department of Molecular Medicine and Surgery, Karolinska Institutet, SE-17176 Stockholm, Sweden. therese.djarv@ki.se
authors.forename: Therese
authors.initials: T
authors.lastname: Djärv
authors.forename: Anna
authors.initials: A
authors.lastname: Wikman
authors.forename: Helena
authors.initials: H
authors.lastname: Nordenstedt
authors.forename: Asif
authors.initials: A
authors.lastname: Johar
authors.forename: Jesper
authors.initials: J
authors.lastname: Lagergren
authors.forename: Pernilla
authors.initials: P
authors.lastname: Lagergren
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D015897:Comorbidity; D003430:Cross-Sectional Studies; D005260:Female; D005764:Gastroesophageal Reflux / Q000150:complications / Q000453:epidemiology* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D009765:Obesity / Q000150:complications / Q000453:epidemiology* / Q000503:physiopathology*; D016017:Odds Ratio; D050177:Overweight; D012042:Registries; D012044:Regression Analysis; D012307:Risk Factors; D011795:Surveys and Questionnaires; D013548:Sweden