SAN FRANCISCO – Subclinical hypothyroidism is a strong independent predictor of cardiovascular mortality in a healthy population at baseline, a national study indicated.
Among 7,883 participants in the National Health and Nutrition Examination Survey III (NHANES III) who were over age 40 years and free of overt hyper- or hypothyroidism, 5.3% had subclinical hypothyroidism as defined by a thyroid-stimulating hormone level of 5-19.99 mIU/L and a thyroxine level of 5-12 mcg/dL. During a mean 12.3 years of follow-up, 25.2% of the subclinical hypothyroid group died of cardiovascular causes, compared with 16.9% of euthyroid controls, Dr. Tushar A. Tuliani reported at the annual meeting of the American College of Cardiology.
Similarly, death due specifically to ischemic heart disease occurred in 15.4% of the subjects with subclinical hypothyroidism, compared with 9.6% of euthyroid controls, added Dr. Tuliani of Wayne State University–Detroit Medical Center.
In a multivariate analysis that adjusted for standard cardiovascular risk factors and demographic variables, individuals with subclinical hypothyroidism had a 20% increased risk of all-cause mortality, a 24% increase in cardiovascular mortality, and a 34% increased risk of death from ischemic heart disease. All of these increases were statistically significant and clinically meaningful, he noted.
NHANES III is an in-depth weighted survey conducted by the Centers for Disease Control and Prevention in a nationally representative population.
Dr. Tuliani reported having no financial conflicts.