European Journal of Epidemiology

, Volume 22, Issue 7, pp 467–472

Smoking and environmental iodine as risk factors for thyroiditis among parous women

  • Maria Rosaria Galanti
  • Sven Cnattingius
  • Fredrik Granath
  • Annika Ekbom-Schnell
  • Anders Ekbom
Review Paper

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.

Keywords

Thyroiditis Hypothyroidism Cigarette smoking Iodine deficiency Cohort study Sweden 

Abbreviations

ATD

Autoimmune thyroid disease

CL

Confidence limits

HR

Hazard ratio

HT

Hashimoto thyroiditis

ICD

International classification of diseases and causes of death

PPT

Post-partum thyroiditis

TPO-Ab

Thyroid peroxidase antibodies

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Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  • Maria Rosaria Galanti
    • 1
    • 2
  • Sven Cnattingius
    • 3
  • Fredrik Granath
    • 1
  • Annika Ekbom-Schnell
    • 4
  • Anders Ekbom
    • 1
  1. 1.Clinical Epidemiology Unit, Department of MedicineKarolinska InstitutetStockholmSweden
  2. 2.Stockholm Centre for Public Health/Tobacco PreventionStockholmSweden
  3. 3.Department of Medical Epidemiology and BiostatisticsKarolinska InstitutetStockholmSweden
  4. 4.Department of MedicineUppsala University HospitalUppsalaSweden

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