[Associations of Life's Crucial 9 and the risk of thyroid dysfunction: a cohort study]

Objective: Exploring the association between Life's Crucial 9 (LC9) and the risk of thyroid dysfunction (TD), as well as its potential predictive capacity. Methods: A total of 247 600 TD-free participants from the UK Biobank were enrolled in the study. The LC9 score was divided into three CVH groups: low (0-), medium (50-), and high (80-100). Cox proportional hazards regression models were used to calculate the HRs and 95%CIs of the risk of TD with LC9 CVH status. Calculate Harrell's concordance index (C-index), net reclassification improvement (NRI), and integrated discrimination improvement (IDI) to evaluate the predictive ability of the LC9 score and Life's Essential 8 (LE8) score. Results: During a median follow-up of 12.3 years, 5 515, 911, and 4 869 new cases of TD, hyperthyroidism, and hypothyroidism were documented, respectively. Participants with a high LE8 CVH group had 57.00% (HR=0.43, 95%CI: 0.38-0.49), 55.00% (HR=0.45, 95%CI: 0.34-0.60), and 58.00% (HR=0.42, 95%CI: 0.37-0.47) lower risk of TD, hyperthyroidism, and hypothyroidism, respectively, than those with low CVH group. Compared with the LE8 score, the improvement in C-index for the LC9 score predicted TD risk was 0.004 (95%CI: 0.001-0.007), the NRI was 0.101 (95%CI: 0.021-0.103), and the IDI was 0.001 (95%CI: 0.000-0.001). Conclusions: The better CVH status, defined by LC9, was associated with a lower risk of TD. Compared to the LE8 score, the LC9 score demonstrated a significant enhancement in both risk discrimination and reclassification capability for TD risk.