title: Body mass index and risk of autoimmune diseases: a study within the Danish National Birth Cohort.
abstract: BACKGROUND
  A possible aetiological link between obesity and certain autoimmune diseases (ADs) has been suggested. We investigated the associations between body mass index (BMI, kg/m2) and 43 ADs.
  
  
  METHODS
  75,008 women participating in the Danish National Birth Cohort were followed during a median time of 11 years. Diagnoses on ADs were retrieved from the Danish National Patient Register. Cox proportional hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated adjusting for potential confounders (smoking, alcohol, parity and socio-occupational status).
  
  
  RESULTS
  During follow-up, 2430 women (3.2%) developed a total of 2607 new-onset ADs. Risk of any autoimmune disease was increased in obese women (HR, 1.27; 95% CI, 1.11 to 1.46) compared with normal weight women (18.5-≤25 kg/m2). Obese women (BMI≥30 kg/m2) were at increased risk of sarcoidosis (HR 3.59; 95% CI, 2.31 to 5.57) and type 1 diabetes mellitus (HR 2.67; 95% CI, 1.71 to 4.17). Risk of dermatitis herpetiformis increased by 14% (95% CI, 1% to 30%) per BMI unit. Conversely, risk of celiac disease and Raynaud's phenomenon decreased by 7% (95% CI, 1% to 13%) and 12% (95% CI, 4% to 19%) per BMI unit, respectively. Further associations between BMI and risk of psoriasis, rheumatoid arthritis and Crohn's disease were suggested.
  
  
  CONCLUSIONS
  BMI was found to be associated with several Ads. This was most pronounced between obesity and risk of sarcoidosis and and risk of type 1 diabetes mellitus. These novel findings need confirmation and the possible role of adipose tissue-derived immunological changes in the development of autoimmune reactions needs consideration.
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark, Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, and Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark and Research Centre for Prevention and Health, Glostrup University Hospital, Glostrup, Denmark rrh@ssi.dk.
authors.forename: Maria C
authors.initials: MC
authors.lastname: Harpsøe
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark, Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, and Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark and Research Centre for Prevention and Health, Glostrup University Hospital, Glostrup, Denmark.
authors.forename: Saima
authors.initials: S
authors.lastname: Basit
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark, Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, and Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark and Research Centre for Prevention and Health, Glostrup University Hospital, Glostrup, Denmark.
authors.forename: Mikael
authors.initials: M
authors.lastname: Andersson
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark, Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, and Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark and Research Centre for Prevention and Health, Glostrup University Hospital, Glostrup, Denmark.
authors.forename: Nete M
authors.initials: NM
authors.lastname: Nielsen
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark, Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, and Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark and Research Centre for Prevention and Health, Glostrup University Hospital, Glostrup, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Frisch
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark, Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, and Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark and Research Centre for Prevention and Health, Glostrup University Hospital, Glostrup, Denmark.
authors.forename: Jan
authors.initials: J
authors.lastname: Wohlfahrt
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark, Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, and Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark and Research Centre for Prevention and Health, Glostrup University Hospital, Glostrup, Denmark.
authors.forename: Ellen A
authors.initials: EA
authors.lastname: Nohr
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark, Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, and Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark and Research Centre for Prevention and Health, Glostrup University Hospital, Glostrup, Denmark.
authors.forename: Allan
authors.initials: A
authors.lastname: Linneberg
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark, Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, and Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark and Research Centre for Prevention and Health, Glostrup University Hospital, Glostrup, Denmark.
authors.forename: Tine
authors.initials: T
authors.lastname: Jess
mesh_terms: D000328:Adult; D001327:Autoimmune Diseases / Q000453:epidemiology*; D015992:Body Mass Index; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D015438:Health Behavior; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D009765:Obesity / Q000453:epidemiology*; D012307:Risk Factors; D012959:Socioeconomic Factors
keywords: Body mass index; autoimmune disease; inflammation; leptin; obesity