Thyroid-stimulating hormone and risk of sudden cardiac death, total mortality and cardiovascular morbidity.

BackgroundPrevious data on the association of thyroid function with total mortality, cardiovascular disease (CVD) outcomes and sudden cardiac death (SCD) are conflicting or limited. We investigated associations of thyroid-stimulating hormone (TSH) with these outcomes in a nationwide population-based prospective cohort study. MethodsWe examined 5211 participants representative of the Finnish population aged 30years in 2000-2001 and followed them for a median of 13.2years. Using Cox proportional hazards regression models adjusted for baseline age, gender, smoking, diabetes, systolic blood pressure and total and high-density lipoprotein cholesterol, we assessed the associations of continuous baseline TSH and TSH categories (low [<0.4mU/L], reference range [0.4-3.4mU/L] and high [>3.4mU/L]) with incident total mortality, SCD, coronary heart disease events, stroke, CVD, major adverse cardiac events and atrial fibrillation. ResultsHigh TSH at baseline was related to a greater risk of total mortality (HR 1.34, 95% CI 1.02-1.76) and SCD (HR 2.28, 95% CI 1.13-4.60) compared with TSH within the reference range. High TSH was not associated with the other outcomes (P.51), whereas low TSH was not associated with any of the outcomes (P.09). TSH at baseline over the full range did not have a linear relation with any of the outcomes (P.17). TSH showed a U-shaped association with total mortality after a restricted cubic spline transformation (P=.01). ConclusionsThyroid function abnormalities could be linked with higher risks of total mortality and SCD. Large-scale randomized studies are needed for evidence-based recommendations regarding treatment of mild thyroid failure.