Subclinical hypothyroidism is an independent risk factor for atherosclerosis and myocardial infarction in elderly women: the Rotterdam Study.
BACKGROUND
Overt hypothyroidism has been found to be associated with cardiovascular disease. Whether subclinical hypothyroidism and thyroid autoimmunity are also risk factors for cardiovascular disease is controversial.


OBJECTIVE
To investigate whether subclinical hypothyroidism and thyroid autoimmunity are associated with aortic atherosclerosis and myocardial infarction in postmenopausal women.


METHODS
Population-based cross-sectional study.


METHODS
A district of Rotterdam, The Netherlands.


METHODS
Random sample of 1149 women (mean age +/- SD, 69.0 +/- 7.5 years) participating in the Rotterdam Study.


METHODS
Data on thyroid status, aortic atherosclerosis, and history of myocardial infarction were obtained at baseline. Subclinical hypothyroidism was defined as an elevated thyroid-stimulating hormone level (>4.0 mU/L) and a normal serum free thyroxine level (11 to 25 pmol/L [0.9 to 1.9 ng/dL]). In tests for antibodies to thyroid peroxidase, a serum level greater than 10 IU/mL was considered a positive result.


RESULTS
Subclinical hypothyroidism was present in 10.8% of participants and was associated with a greater age-adjusted prevalence of aortic atherosclerosis (odds ratio, 1.7 [95% CI, 1.1 to 2.6]) and myocardial infarction (odds ratio, 2.3 [CI, 1.3 to 4.0]). Additional adjustment for body mass index, total and high-density lipoprotein cholesterol level, blood pressure, and smoking status, as well as exclusion of women who took beta-blockers, did not affect these estimates. Associations were slightly stronger in women who had subclinical hypothyroidism and antibodies to thyroid peroxidase (odds ratio for aortic atherosclerosis, 1.9 [CI, 1.1 to 3.6]; odds ratio for myocardial infarction, 3.1 [CI, 1.5 to 6.3]). No association was found between thyroid autoimmunity itself and cardiovascular disease. The population attributable risk percentage for subclinical hypothyroidism associated with myocardial infarction was within the range of that for known major risk factors for cardiovascular disease.


CONCLUSIONS
Subclinical hypothyroidism is a strong indicator of risk for atherosclerosis and myocardial infarction in elderly women.
Hak
A E
AE
Department of Epidemiology and Biostatistics, Erasmus University Medical School, Rotterdam, The Netherlands.
Pols
H A
HA
Visser
T J
TJ
Drexhage
H A
HA
Hofman
A
A
Witteman
J C
JC
D000368:Aged; D001018:Aortic Diseases / Q000209:etiology*; D001161:Arteriosclerosis / Q000209:etiology*; D001323:Autoantibodies / Q000097:blood; D001327:Autoimmune Diseases / Q000150:complications*; D016009:Chi-Square Distribution; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007037:Hypothyroidism / Q000150:complications*; D007453:Iodide Peroxidase / Q000276:immunology; D009203:Myocardial Infarction / Q000209:etiology*; D009426:Netherlands; D012044:Regression Analysis; D012307:Risk Factors; D013959:Thyroid Diseases / Q000150:complications*
D001323:Autoantibodies; D007453:Iodide Peroxidase