title: Smoking and environmental iodine as risk factors for thyroiditis among parous women.
abstract: OBJECTIVE
  To elucidate whether exposure to some environmental factors, i.e. cigarette smoking and iodine deficiency influence the risk of thyroiditis.
  
  
  METHODS
  We identified a cohort of 874, 507 parous women with self-reported information on smoking during pregnancy registered in the Swedish Medical Birth Registry from September 1983 through December 1997. Hospital diagnoses of thyroiditis (n = 286) and hypothyroidism (n = 690) following entry into the cohort were identified by record-linkage with the national Inpatient Registry. The hazard ratio (HR) of smokers compared to non-smokers and the corresponding 95% confidence limits (CL) were estimated by Cox regression.
  
  
  RESULTS
  Smoking was inversely associated with risk of overt thyroiditis (adjusted HR = 0.72; CL = 0.54-0.95), even when diagnoses of primary hypothyroidism were included. However, a diagnosis of thyroiditis within 6 months from a childbirth was positively associated with smoking (adjusted HR = 1.88; CL = 0.94-3.76). Being born in areas of endemic goiter was not associated to hospital admission for thyroiditis. Thyroiditis patients who were smokers had more often than non-smokers a co-morbidity with other autoimmune disorders.
  
  
  CONCLUSIONS
  Smoking may increase the risk of thyroiditis occurring in the post-partum period and influence the clinical expression of other thyroiditis, especially when occurring as part of a polymorphic autoimmune disease.
authors.affiliation: Clinical Epidemiology Unit, Department of Medicine, Karolinska Institutet, Karolinska Hospital M9:01, Stockholm, 171 76, Sweden. rosaria.galanti@sll.se
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Galanti
authors.forename: Sven
authors.initials: S
authors.lastname: Cnattingius
authors.forename: Fredrik
authors.initials: F
authors.lastname: Granath
authors.forename: Annika
authors.initials: A
authors.lastname: Ekbom-Schnell
authors.forename: Anders
authors.initials: A
authors.lastname: Ekbom
mesh_terms: D001327:Autoimmune Diseases / Q000453:epidemiology; D001719:Birth Certificates; D015897:Comorbidity; D019353:Endemic Diseases; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000175:diagnosis / Q000453:epidemiology / Q000276:immunology; D007455:Iodine / Q000172:deficiency*; D050032:Postpartum Thyroiditis / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology; D011247:Pregnancy; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D013548:Sweden / Q000453:epidemiology
chemical_list: D007455:Iodine