Cigarette smoking and the risk of goitre and thyroid nodules amongst parous women.
OBJECTIVE
To clarify the mechanisms by which smoking is associated to toxic and nontoxic goitre and thyroid nodules.


METHODS
Cohort study.


METHODS
Sweden.


METHODS
A cohort of 874,507 parous women identified through the Medical Birth Registry, with smoking behaviour assessed through self-reported information at the first pre-natal visit, and follow-up between 1983 and 1997.


METHODS
Hospital diagnoses of toxic and nontoxic goitre and thyroid nodules, identified by record-linkage with the national Inpatient Registry. Cox regression was employed to estimate the hazard ratio (HR) of smokers compared with nonsmokers and the corresponding 95% confidence limits (CL).


RESULTS
There was a significantly increased risk of goitre and nodules amongst smokers. The positive association was stronger for toxic (age adjusted HR = 1.94, CL = 1.74-2.16) than for nontoxic goitre and nodules (age-adjusted HR = 1.26; CL = 1.14-1.38). There was generally no clear risk trend with regard to amount smoked (below and above 10 cigarettes per day). Elevated body mass attenuated these associations, whilst being born in Swedish areas of endemic goitre enhanced the association with nontoxic goitre and nodules.


CONCLUSIONS
Smoking enhances the risk of thyroid goitre and nodules requiring hospital admission. Iodine deficiency and body weight are likely to be important modifiers of the risk of thyroid hyperplastic diseases amongst smokers.
Galanti
M R
MR
Department of Medicine, Clinical Epidemiology Unit, Karolinska Institutet, Stockholm, Sweden. rosaria.galanti@sll.se
Granath
F
F
Cnattingius
S
S
Ekbom-Schnell
A
A
Ekbom
A
A
D000328:Adult; D015992:Body Mass Index; D001835:Body Weight; D005260:Female; D006042:Goiter / Q000209:etiology / Q000473:pathology; D006801:Humans; D006965:Hyperplasia / Q000473:pathology; D010298:Parity; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012042:Registries; D012907:Smoking / Q000009:adverse effects*; D013548:Sweden; D013959:Thyroid Diseases / Q000209:etiology* / Q000473:pathology; D013961:Thyroid Gland / Q000473:pathology; D016606:Thyroid Nodule / Q000209:etiology / Q000473:pathology