title: Body mass index and physical activity and the risk of diverticular disease: a systematic review and meta-analysis of prospective studies.
abstract: OBJECTIVE
  We conducted a systematic review and meta-analysis of prospective studies of the association between body mass index (BMI) and physical activity and diverticular disease risk.
  
  
  METHODS
  PubMed and Embase databases were searched up to February 7, 2017. Summary relative risks and 95% confidence intervals (95% CIs) were calculated using a random effects model and nonlinear associations were modeled using fractional polynomial models.
  
  
  RESULTS
  Six cohort studies of BMI and diverticular disease risk (28,915 cases, 1,636,777 participants) and five cohort studies of physical activity and diverticular disease risk (2080 cases, 147,869 participants) were included. The summary relative risk (RR) of incident diverticular disease for a 5 unit BMI increment was 1.28 (95% CI: 1.18-1.40, I2= 77%, n = 6) for diverticular disease, 1.31 (95% CI: 1.09-1.56, I2= 74%, n = 2) for diverticulitis, and 1.20 (95% CI: 1.04-1.40, I2= 56%, n = 3) for diverticular disease complications. There was no evidence of a nonlinear association between BMI and diverticular disease risk (pnonlinearity= 0.22), and risk increased even within the normal weight range. Compared to a BMI of 20, the summary RR for a BMI of 22.5, 25.0, 27.5, 30.0, 32.5, 35.0, 37.5, and 40.0 was 1.15 (1.07-1.23), 1.31 (1.17-1.47), 1.50 (1.31-1.71), 1.71 (1.52-1.94), 1.96 (1.77-2.18), 2.26 (2.00-2.54), 2.60 (2.11-3.21), and 3.01 (2.06-4.39), respectively. The summary RR was 0.76 (95% CI: 0.63-0.93, I2= 54%, n = 5) for high vs. low physical activity and 0.74 (95% CI: 0.57-0.97, I2= 39.5%, pheterogeneity= 0.20, n = 2) for high vs. low vigorous physical activity.
  
  
  CONCLUSIONS
  These results suggest that even moderate increases in BMI may increase the risk of diverticular disease as well as diverticular disease complications and that a higher level of physical activity may reduce the risk.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, St. Mary's Campus, Norfolk Place, Paddington, London, W2 1PG, UK. d.aune@imperial.ac.uk.|Department of Public Health and General Practice, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway. d.aune@imperial.ac.uk.|Bjørknes University College, Oslo, Norway. d.aune@imperial.ac.uk.
authors.forename: Dagfinn
authors.initials: D
authors.lastname: Aune
authors.affiliation: Department of Public Health and General Practice, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Abhijit
authors.initials: A
authors.lastname: Sen
authors.affiliation: Department of Epidemiology and Preventive Medicine, Regensburg University Medical Center, Regensburg, Germany.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Leitzmann
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, St. Mary's Campus, Norfolk Place, Paddington, London, W2 1PG, UK.
authors.forename: Teresa
authors.initials: T
authors.lastname: Norat
authors.affiliation: Department of Preventive Cardiology, Oslo University Hospital, University of Oslo, Oslo, Norway.
authors.forename: Serena
authors.initials: S
authors.lastname: Tonstad
authors.affiliation: Department of Public Health and General Practice, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Lars J
authors.initials: LJ
authors.lastname: Vatten
mesh_terms: D015992:Body Mass Index; D000076385:Diverticular Diseases / Q000150:complications / Q000453:epidemiology*; D015444:Exercise; D006801:Humans; D015994:Incidence; D009765:Obesity / Q000150:complications / Q000453:epidemiology*; D012307:Risk Factors; D012680:Sensitivity and Specificity; D055105:Waist Circumference; D049629:Waist-Hip Ratio
keywords: Body mass index; Diverticular disease; Meta-analysis; Physical activity; Systematic review