Abstract P200: Validity of self-reported hypothyroidism: Associations with cardiovascular risk factors in the CARDIA Study
BACKGROUND: Hypothyroidism (HYPOT), defined as having low levels of free thyroxine and elevated levels of thyroid-stimulating hormone (TSH), is a common condition linked to many adverse cardiovascular risk factors. Observational studies often rely on self-reported medical history that may or may not accurately reflect the presence of a condition or its adequate control.
METHODS: We examined the association between self-reported HYPOT and levels of risk factors commonly altered by HYPOT using the Year 25 (2010-2011) CARDIA Study data. Systolic blood pressure, total, LDL- and HDL-cholesterol, triglycerides, body mass index (BMI), and Center for Epidemiologic Studies Depression (CES-D) score were measured using standardized methods. Crude means or geometric means were compared by HYPOT status with t-tests. Least-squared means adjusted for age, race, sex, center, smoking status, education, and BMI were estimated by HYPOT status using linear regression, and repeated with additional adjustment for levothyroxine or synthyroid use.
RESULTS: After excluding 48 cases of hyperthyroidism, 4.6% (131/2851) of participants self-reported having HYPOT; mean age was 50.1 years, 55.3% were women, and 52.4% were white. Compared to those without HYPOT, those with HYPOT were more likely to be white (75.6% vs. 51.3%) and women (85.5% vs. 53.9%); crude mean systolic blood pressure was lower (114.9 vs. 120.3 mmHg, p=0.0002) and HDL-c was higher (61.7 vs. 57.9 mg/dL, p=0.03). After multivariable adjustment (Table), only BMI and triglycerides differed by HYPOT status. Adjustment for thyroid medication use did not materially alter mean differences.
CONCLUSION: Self-reported hypothyroidism was inconsistently associated with risk factors commonly altered by thyroid abnormalities, regardless of medication status. These data suggest that TSH measurement is necessary to accurately identify individuals with low thyroid function leading to risk factor disturbances.
- © 2012 by American Heart Association, Inc.