Research Article

Association between the Systemic Immune-Inflammation Index and Thyroid Function in U.S. Adults

Table 1

Baseline characteristics of the NHANES (2007–2012) study population in SII tertiles.

CharacteristicsTotalSystemic immune-inflammatory indexp-Value
Tertile 1 (13.750–387.529)Tertile 2 (387.545–596.077)Tertile 3 (596.111–4085.000)

Numbers6,8752,2922,2912,292
Age (years)46.87 ± 0.4046.04 ± 0.5547.07 ± 0.4747.45 ± 0.530.064
Sex<0.001
 Male49.81 (48.69, 50.93)53.86 (51.09, 56.60)50.57 (47.82, 53.32)45.22 (42.90, 47.57)
 Female50.19 (49.07, 51.32)46.14 (43.40, 48.91)49.43 (46.68, 52.18)54.78 (52.44, 57.10)
Race<0.001
 Mexican American7.75 (5.98, 9.98)7.77 (6.12, 9.81)8.02 (6.02, 10.61)7.45 (5.47, 10.06)
 Non-Hispanic Black9.87 (7.72, 12.53)14.50 (11.38, 18.31)7.95 (6.20, 10.15)7.42 (5.58, 9.81)
 Non-Hispanic White71.74 (66.99, 76.05)67.75 (62.74, 72.39)72.23 (67.49, 76.53)75.00 (69.67, 79.66)
 Other Hispanic4.87 (3.52, 6.70)4.68 (3.45, 6.33)5.22 (3.68, 7.34)4.70 (3.17, 6.90)
 Other race5.78 (4.75, 7.02)5.30 (4.00, 6.98)6.58 (5.11, 8.43)5.44 (4.15, 7.11)
Marital status0.006
 Nonsingle64.14 (61.18, 67.00)66.31 (62.70, 69.74)65.18 (61.40, 68.78)61.05 (57.59, 64.39)
 Single35.86 (33.00, 38.82)33.69 (30.26, 37.30)34.82 (31.22, 38.60)38.96 (35.61, 42.41)
Education level0.221
 <High school5.77 (4.94, 6.72)5.79 (4.83, 6.93)6.11 (5.02, 7.43)5.39 (4.38, 6.63)
 Graduated from high school35.82 (32.65, 39.11)34.11 (30.50, 37.90)35.28 (32.30, 38.39)37.96 (33.04, 43.14)
 College education or above58.42 (54.84, 61.92)60.11 (56.24, 63.85)58.61 (54.94, 62.18)56.65 (51.40, 61.75)
 Family PIR3.05 ± 0.063.07 ± 0.073.14 ± 0.072.93 ± 0.080.010
Family PIR groups0.004
 <113.85 (12.06, 15.86)13.90 (11.95, 16.11)13.28 (11.19, 15.68)14.39 (12.21, 16.88)
 ≥1, <335.61 (32.73, 38.60)35.33 (31.71, 39.13)32.94 (29.66, 36.40)38.54 (34.96, 42.26)
 ≥350.54 (46.80, 54.28)50.77 (46.60, 54.93)53.78 (49.45, 58.05)47.07 (42.36, 51.83)
Alcohol use0.406
 Never10.38 (9.10, 11.82)11.26 (9.32, 13.55)9.21 (7.91, 10.70)10.73 (9.00, 12.75)
 Former16.14 (14.15, 18.35)14.79 (13.07, 16.70)16.43 (13.77, 19.48)17.12 (14.36, 20.29)
 Mild34.54 (31.96, 37.22)34.76 (31.39, 38.28)35.62 (32.53, 38.82)33.26 (29.23, 37.54)
 Moderate16.90 (15.33, 18.60)17.55 (15.21, 20.17)17.23 (15.33, 19.31)15.95 (13.29, 19.03)
 Heavy22.04 (20.47, 23.69)21.64 (19.21, 24.28)21.52 (19.35, 23.86)22.94 (20.70, 25.35)
Smoking status0.002
 Never53.26 (50.95, 55.57)56.11 (53.62, 58.57)53.32 (50.17, 56.44)50.53 (46.37, 54.68)
 Former25.19 (23.86, 26.55)24.46 (22.18, 26.88)26.84 (24.57, 29.24)24.21 (22.12, 26.43)
 Now21.55 (19.58, 23.66)19.44 (16.76, 22.42)19.84 (17.41, 22.52)25.26 (22.13, 28.67)
 BMI (kg/m2)28.67 ± 0.1127.87 ± 0.1928.69 ± 0.1629.40 ± 0.20<0.001
BMI groups0.010
 ≤18.51.54 (1.15, 2.06)2.06 (1.36, 3.11)1.22 (0.78, 1.92)1.37 (0.88, 2.12)
 >18.5, ≤25.030.01 (28.35, 31.71)32.43 (29.64, 35.34)28.59 (25.92, 31.42)29.15 (26.33, 32.14)
 >25.0, ≤30.034.15 (32.47, 35.87)35.19 (32.13, 38.38)35.13 (32.33, 38.03)32.19 (29.42, 35.09)
 >3034.31 (32.57, 36.08)30.33 (27.20, 33.65)35.06 (32.61, 37.59)37.29 (34.10, 40.59)
Diabetes0.283
 No86.34 (84.95, 87.62)86.86 (85.15, 88.40)86.91 (85.02, 88.60)85.27 (82.85, 87.40)
 Yes13.66 (12.38, 15.05)13.14 (11.60, 14.85)13.09 (11.40, 14.98)14.73 (12.60, 17.15)
 UIC (µg/L)382.75 ± 122.44252.37 ± 35.44222.54 ± 11.42666.56 ± 357.350.290
UIC groups0.560
 <10032.60 (30.96, 34.29)33.47 (30.45, 36.63)32.35 (29.35, 35.50)32.04 (29.64, 34.55)
 ≥100, <30048.39 (46.31, 50.48)49.10 (46.37, 51.84)47.63 (44.28, 50.99)48.48 (45.83, 51.14)
 ≥30019.01 (17.23, 20.92)17.43 (15.44, 19.62)20.02 (16.61, 23.94)19.47 (17.70, 21.38)
HbA1c (%)5.60 ± 0.025.57 ± 0.025.60 ± 0.025.62 ± 0.030.238
ALT (IU/L)26.19 ± 0.2626.83 ± 0.4826.46 ± 0.5025.32 ± 0.470.071
AST (IU/L)26.21 ± 0.2627.25 ± 0.5025.92 ± 0.4325.51 ± 0.400.022
Cr (mg/dL)0.88 ± 0.000.88 ± 0.010.88 ± 0.010.87 ± 0.010.383
TC (mmol/L)5.10 ± 0.025.02 ± 0.035.16 ± 0.035.11 ± 0.030.009
FT3 (pg/mL)3.18 ± 0.013.21 ± 0.013.18 ± 0.013.16 ± 0.010.002
FT4 (ng/dL)0.80 ± 0.010.80 ± 0.010.79 ± 0.010.81 ± 0.010.044
TT3 (nmol/L)1.79 ± 0.011.80 ± 0.021.80 ± 0.021.77 ± 0.020.139
TT4 (µg/dL)7.84 ± 0.047.74 ± 0.067.79 ± 0.047.97 ± 0.05<0.001
TSH (μIU/mL)2.04 ± 0.062.03 ± 0.042.03 ± 0.122.06 ± 0.090.925
FT3/FT44.11 ± 0.034.14 ± 0.034.13 ± 0.034.06 ± 0.030.016
TG (ng/mL)16.14 ± 0.5714.83 ± 0.5715.01 ± 0.8118.52 ± 1.390.062
TGAb (IU/mL)9.91 ± 1.0411.19 ± 2.7511.95 ± 2.586.65 ± 1.200.027
TPOAb (IU/mL)21.65 ± 1.2419.47 ± 2.1220.31 ± 2.2725.04 ± 2.640.236

Note: Continuous variables were presented as mean ± SEM, p-value was calculated by survey-weighted linear regression analysis. Categorical variables were presented as the percentage (95% confidence interval), p-value was calculated by survey-weighted chi-square test. NHANES, National Health and Nutrition Examination Survey; PIR, poverty income ratio; BMI, body mass index; UIC, urine iodine concentration; HbA1c, glycated hemoglobin; ALT, alanine aminotransferase; AST, aspartate aminotransferase; Cr, creatinine; TC, total cholesterol; FT3, free triiodothyronine; FT4, free thyroxine; TT3, total triiodothyronine; TT4, total thyroxine; TSH, thyroid-stimulating hormone; TG, thyroglobulin; TGAb, thyroglobulin antibodies; and TPOAb, thyroid peroxidase antibodies. Bold values signify the statistically significant variables clearly distinguishable from those that are not.