Cardiovascular Health Protects against Thyroid Dysfunction: Findings from the UK Biobank

Background: Few studies have investigated the association between cardiovascular health (CVH) and thyroid dysfunction, and the modifying role of depression or anxiety remains unclear. Methods: This longitudinal study included 360,332 UK Biobank participants without thyroid disease at baseline and with complete CVH scores. We examined the associations between CVH and the risks of hyperthyroidism and hypothyroidism using Cox proportional hazards regression models, quantified the relative contributions of CVH components using weighted quantile sum regression, and evaluated the mediating role of inflammatory markers. Furthermore, we investigated the modifying effects of depression and anxiety on these associations. A multi-state model was used to explore disease trajectories. Results: During a median follow-up of 12.53 years, 1,533 and 7,542 participants developed hyperthyroidism and hypothyroidism, respectively. After multivariable adjustment, each 5-point increase in CVH score was associated with a 7% (95% confidence interval [CI], 4% to 9%) lower risk of hyperthyroidism and an 8% (95% CI, 7% to 9%) lower risk of hypothyroidism. A high CVH score was associated with a 50% (95% CI, 37% to 60%) lower risk of hyperthyroidism and a 45% (95% CI, 38% to 50%) lower risk of hypothyroidism. Among the CVH components, obesity and tobacco exposure contributed most to disease risk. Inflammatory markers partially mediated these associations. Depression and anxiety modified the association between CVH and hypothyroidism, and CVH showed a protective effect across the disease trajectories. Conclusion: Maintaining favorable CVH was associated with a lower risk of thyroid dysfunction, particularly among individuals with good mental health.