Free Triiodothyronine Levels are Related to Executive Function and Scene Memory in Type 2 Diabetes Mellitus Patients Without Diagnosed Thyroid Diseases

Figures & data

Table 1 Comparation of Clinical Parameters and Neuropsychological Test Results Between MCI and Non-MCI Group

	All Individuals	MCI (n=108)	Non-MCI (n=147)	P
Age (year)	59 (53–66)	61 (56–68)	57 (52–63)	0.002^‡*
Female (n, %)	101 (39.6)	53 (49.1)	48 (32.7)	0.108^§
Education (year)	11 (9–12)	9 (9–12)	12 (9–13)	0.008^‡*
BMI (Kg/m2)	24.68 (22.76–27.04)	24.48 (22.67–27.05)	24.81 (22.97–26.87)	0.919^‡
DM Duration (year)	10 (6–15)	8 (10–15)	10 (6–14)	0.044^‡*
HBP Duration (year)	5 (0–12)	8 (0–16)	8 (0–10)	0.007^‡*
Smoking (n, %)	91 (35.7)	33 (30.6)	58 (39.5)	0.182^§
HbA1c	8.7 (7.6–10.4)	9.0 (8.0–10.0)	8.4 (7.3–10.0)	0.012^‡*
FPG (mmol/l)	7.80 (6.57–10.00)	7.90 (6.40–10.50)	7.70 (6.60–9.72)	0.444^‡
FCP (pmol/l)	0.82 (0.47–1.32)	0.92 (0.521–1.378)	0.77 (0.45–1.23)	0.054^‡
HOMA-IR	0.28 (0.16–0.49)	0.33 (0.18–0.55)	0.261 (0.15–0.46)	0.033^‡*
TG (mmol/l)	1.50 (1.00–2.25)	1.67 (0.94–2.57)	1.47 (1.04–2.11)	0.292^‡
TC (mmol/l)	4.5±1.16	4.53±1.18	4.51±1.13	0.901^†
HDL (mmol/l)	1.10 (0.94–1.27)	1.09 (0.93–1.27)	1.10 (0.94–1.28)	0.907^‡
LDL (mmol/l)	2.74 (2.18–3.39)	2.72 (2.27–3.37)	2.77 (2.17–3.39)	0.924^‡
FT3 (pg/mL)	3.86 (2.87–4.62)	3.49 (2.74–4.38)	4.05 (3.04–4.72)	0.004^‡*
FT4 (ng/dl)	15.48 (1.39–18.22)	14.08 (1.34–17.39)	16.14 (1.44–18.38)	0.038^‡*
TSH (uIU/l)	2.00 (1.30–3.02)	2.15 (1.45–3.15)	1.90 (1.24–2.69)	0.099^‡
FT3/TSH	1.93 (1.11–2.88)	1.66 (0.95–2.62)	2.07 (1.35–3.33)	0.016^‡*
FT4/TSH	5.42 (0.85–10.10)	2.92 (0.71–8.14)	6.90 (1.19–11.37)	0.002^‡*
MoCA	26 (24–28)	23 (21–24)	27 (26–28)	<0.001^‡*
DST	13 (10–13)	11 (9–12)	29 (29–30)	<0.001^‡*
VFT	16 (14–19)	14 (13–17)	17 (14–21)	<0.001^‡*
CDT	4 (3–4)	3 (2–4)	4 (3–4)	<0.001^‡*
TMTA	58 (48–75)	70 (55–84)	55 (45–65)	<0.001^‡*
TMTB	148 (114–200)	176 (141–234)	127 (100–168)	<0.001^‡*
AVLT-IR	18 (15–21)	16 (13–19)	19 (16–23)	<0.001^‡*
AVLT-DR	6 (4–7)	5 (3–6)	6 (5–9)	<0.001^‡*
LMT	10 (7–13)	8 (4–10)	12 (9–15)	<0.001^‡*

Notes: The data are presented as n (%), the mean ± SD, or the median (inter-quartile range) unless otherwise specified. ^†Student’s t-test was employed for normally distributed variables. ^‡The Mann–Whitney U-test was employed for asymmetrically distributed variables. ^§The Chi-square test was employed for categorical variables. *p<0.05.

Abbreviations: MCI, individuals with mild cognitive impairment; Non-MCI, individuals without mild cognitive impairment; BMI, body mass index; DM, diabetes mellitus; HBP, high blood pressure; FPG, fasting plasma glucose; FCP, fasting C peptide; HOMA-IR, Homeostasis model assessment for insulin resistance; TG, triglycerides; TC, Total cholesterol; LDL, low density lipoprotein cholesterol; HDL, high density lipoprotein cholesterol; FT3, Free triiodothyronine; FT4, free thyroxine; TSH, thyroid stimulating hormone; MoCA, Montreal Cognitive Assessment; DST, Digit Span Test; VFT, Verbal Fluency Test; CDT, Clock Drawing Test; TMTA, Trail Making Test-A; TMTB, Trail Making Test-B; AVLT-IR, Auditory Verbal Learning test- immediate recall; AVLT-DR, Auditory Verbal Learning test-delayed recall; LMT, logical memory test.

Table 2 Binary Logistic Regression Analysis of Independent Risk Factor for MCI Risk

	P	OR	95% CL of OR
			Lower	Higher
Age	0.215	0.977	0.942	1.014
Education	<0.001*	1.208	1.103	1.323
DM Duration	0.163	0.965	0.918	1.014
HBP Duration	0.041*	0.971	0.943	0.999
HbA1c	0.043*	0.886	0.788	0.996
HOMA-IR	0.038*	0.394	0.163	0.948

Note: *p<0.05.

Abbreviations: MCI, mild cognitive impairment; DM, diabetes mellitus; HBP, high blood pressure; HOMA-IR, Homeostasis model assessment for insulin resistance.

Table 3 Association Between FT3 and Cognitive Function

	Model 1 ^a		Model 2 ^b
	R	P	R	P
MoCA	0.145	0.023*	0.092	0.152
DST	0.137	0.031*	0.117	0.067
VFT	0.244	<0.001*	0.229	<0.001*
CDT	0.092	0.149	0.066	0.299
TMTA	0.013	0.835	0.017	0.787
TMTB	−0.134	0.035*	−0.121	0.057
AVLT-IR	0.059	0.360	0.020	0.756
AVLT-DR	−0.002	0.971	−0.025	0.695
LMT	0.201	<0.001*	0.166	0.009*

Notes: ^aAdjusted for age, education, DM duration, HBP duration and HbA1c. ^bAdjusted for age, education, DM duration, HBP duration, HbA1c and HOMA-IR. *p<0.05.

Abbreviations: FT3, Free triiodothyronine; MoCA, Montreal Cognitive Assessment; DST, Digit Span Test; VFT, Verbal Fluency Test; CDT, Clock Drawing Test; TMTA, Trail Making Test-A; TMTB, Trail Making Test-B; AVLT-IR, Auditory Verbal Learning test- immediate recall; AVLT-DR, Auditory Verbal Learning test-delayed recall; LMT, logical memory test; DM, diabetes mellitus; HBP, high blood pressure; HOMA-IR, Homeostasis model assessment for insulin resistance.

Table 4 Multiple Linear Regression Analysis of the Factors Influencing VFT or LMT

	VFT			LMT
	P	95% CL of β		P	95% CL of β
		Lower	Higher		Lower	Higher
Age	0.306	−0.099	0.031	0.282	−0.114	0.033
Education	<0.001*	0.243	0.540	0.007*	0.066	0.402
DM Duration	0.874	−0.096	0.081	0.498	−0.135	0.066
HBP Duration	0.853	−0.055	0.046	0.317	−0.087	0.028
HbA1c	0.004*	−0.539	−0.106	0.778	−0.280	0.210
HOMA-IR	0.452	−2.115	0.945	0.016*	−3.870	−0.405
FT3	<0.001*	0.408	1.302	0.009*	0.171	1.183

Note: *p<0.05.

Abbreviations: DM, diabetes mellitus; HBP, high blood pressure; HOMA-IR, Homeostasis model assessment for insulin resistance; FT3, Free triiodothyronine; VFT, Verbal Fluency Test; LMT, logical memory test; BMI, body mass index.