Table 4.

HRs (95% CI) of Dementia by Categorical Distribution of Thyroid Hormone Levels, ARIC 1990 - 2017

TSH	Lowest 5%, ≤ 0.54 mIU/L (number of total = 626; number of events = 116)	Middle 90%, 0.55 - 5.97 mIU/L (number of total = 11,226; number of events = 1,998)	Highest 5%, ≥ 5.98 mIU/L (number of total = 629; number of events = 121)	TSH per 6.35 mIU/L (number of total = 12,481; number of events = 2,235)
Model 1 HR	1.24* (1.03 - 1.50)	1 (Ref)	0.93 (0.77 - 1.12)	1.03 (0.98 - 1.07)
Model 2 HR	1.13 (0.92 - 1.39)	1 (Ref)	0.94 (0.77 - 1.14)	1.03 (0.98 - 1.07)
Model 3 HR	1.09 (0.87 - 1.36)	1 (Ref)	0.90 (0.73 - 1.11)	1.02 (0.97 - 1.07)
FT4	Lowest 5%, ≤ 0.89 ng/dL (number of total = 628; number of events = 123)	Middle 90%, 0.90 - 1.35 ng/dL (number of total = 11,170; number of events = 1,981)	Highest 5%, ≥ 1.36 ng/dL (number of total = 683; number of events = 131)	FT4 per SD (0.19 ng/dL) (number of total = 12,481; number of events = 2,235)
Model 1 HR	0.96 (0.79 - 1.18)	1 (Ref)	1.30* (1.08 - 1.55)	1.06* (1.02 - 1.09)
Model 2 HR	0.96 (0.78 - 1.17)	1 (Ref)	1.26* (1.05 - 1.51)	1.05* (1.01 - 1.09)
Model 3 HR	0.95 (0.77 - 1.16)	1 (Ref)	1.23* (1.02 - 1.48)	1.05* (1.01 - 1.09)

^*P-value < 0.05. Model 1: age, sex, race-center, APOE ε4, income, education and TSH or FT4. Model 2: model 1 + BMI, smoking status, hypertension, diabetes, drinking status, HDL cholesterol and total cholesterol. Model 3: model 2 + prevalent CVD and baseline thyroid medication use. HR: hazard ratio; CI: confidence interval; ARIC: Atherosclerosis Risk in Communities; TSH: thyroid-stimulating hormone; FT4: free thyroxine; BMI: body mass index; HDL: high-density lipoprotein; CVD: cardiovascular disease.