title: Inverse Association Between Poor Oral Health and Inflammatory Bowel Diseases.
abstract: OBJECTIVE
  The hygiene hypothesis (a lack of childhood exposure to microorganisms increases susceptibility to allergic diseases by altering immune development) has been proposed as an explanation for the increasing incidence of inflammatory bowel disease (IBD). However, there are few data on the relationship between oral hygiene and development of IBD, and study results have been inconsistent. We investigated the association between poor oral health and risks of IBD, ulcerative colitis (UC), and Crohn's disease (CD).
  
  
  METHODS
  We performed a population-based cohort study of 20,162 individuals followed for 40 years (from 1973 to 2012). Residents of 2 municipalities of Uppsala County, Sweden (N = 30,118), 15 years or older, were invited, and among them 20,333 were examined for tooth loss, dental plaques, and oral mucosal lesions at the time of study entry. Other exposure data were collected from questionnaires. Patients who later developed IBD (UC or CD) were identified by international classification codes from Swedish National Patient and Cause of Death Registers. Cox proportional hazards regression was used to estimate hazard ratios for IBD, UC, and CD.
  
  
  RESULTS
  From National Patient and Cause of Death Registers, we identified 209 individuals who developed IBD (142 developed UC and 67 developed CD), with an incidence rate of 37.3 per 100,000 person-years. We found an inverse relationship between poor oral health and IBD, especially in individuals with severe oral problems. Loss of 5-6 teeth of the 6 teeth examined was associated with a lower risk of IBD (hazard ratio, 0.56; 95% confidence interval, 0.32-0.98). Having dental plaques that covered more than 33% of tooth surface was negatively associated with CD (hazard ratio, 0.32; 95% confidence interval, 0.10-0.97).
  
  
  CONCLUSIONS
  In a population-based cohort study of more than 20,000 people in Sweden, we associated poor oral health with reduced risk of future IBD.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; Department of Reproductive Endocrinology, West China Second University Hospital, Sichuan University, Chengdu, China. Electronic address: weiyao.yin@ki.se.
authors.forename: Weiyao
authors.initials: W
authors.lastname: Yin
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; Department of Pediatrics, Örebro University Hospital, Örebro, Sweden.
authors.forename: Jonas F
authors.initials: JF
authors.lastname: Ludvigsson
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Dental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Ann
authors.initials: A
authors.lastname: Roosaar
authors.affiliation: Maxillofacial Unit, Halmstad Hospital Halland, Halmstad, Sweden.
authors.forename: Tony
authors.initials: T
authors.lastname: Axéll
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden. Electronic address: weimin.ye@ki.se.
authors.forename: Weimin
authors.initials: W
authors.lastname: Ye
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D015994:Incidence; D015212:Inflammatory Bowel Diseases / Q000453:epidemiology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009909:Oral Health; D011446:Prospective Studies; D018570:Risk Assessment; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult
keywords: Dental Care; Epidemiology; Microbiota; Risk Factor