Table 2 Baseline characteristics of participants categorized by AIP quartiles

Age (years), mean ± SD

59.56 ± 9.59

59.14 ± 9.23

59.09 ± 9.14

58.50 ± 8.78

0.002^a

Age ≥ 60 years, n (%)

984 (45.8%)

954 (44.4%)

957 (44.5%)

886 (41.2%)

0.019^b

Men, n (%)

1102 (51.3%)

1010 (47.0%)

936 (43.6%)

937 (43.6%)

 < 0.001^b

Married, n (%)

1788 (83.2%)

1765 (82.1%)

1789 (83.2%)

1847 (85.9%)

0.007^b

Rural residence, n (%)

1553 (72.2%)

1449 (67.4%)

1374 (63.9%)

1269 (59.0%)

 < 0.001^b

Education level, n (%)

0.065^b

 No formal education

656 (30.5%)

642 (29.9%)

636 (29.6%)

601 (28.0%)

 Primary school

901 (41.9%)

893 (41.6%)

870 (40.5%)

863 (40.1%)

 Middle or high school

544 (25.3%)

547 (25.5%)

582 (27.1%)

606 (28.2%)

 College or above

49 (2.3%)

67 (3.1%)

61 (2.8%)

80 (3.7%)

Smoking status, n (%)

0.001^b

 Never

1246 (58.0%)

1304 (60.7%)

1363 (63.4%)

1354 (63.0%)

 Former

189 (8.8%)

165 (7.7%)

178 (8.3%)

195 (9.1%)

 Current

715 (33.3%)

680 (31.6%)

608 (28.3%)

601 (28.0%)

Drinking status, n (%)

 < 0.001^b

 Never

1130 (52.6%)

1265 (58.9%)

1322 (61.5%)

1363 (63.4%)

 Former

149 (6.9%)

184 (8.6%)

213 (9.9%)

162 (7.5%)

 Current

871 (40.5%)

700 (32.6%)

614 (28.6%)

625 (29.1%)

SBP (mmHg), mean ± SD

126.48 ± 21.25

128.08 ± 21.05

130.34 ± 21.53

131.96 ± 20.96

 < 0.001^a

DBP (mmHg), mean ± SD

73.08 ± 12.12

74.28 ± 11.73

76.11 ± 12.31

77.21 ± 12.00

 < 0.001^a

Diabetes, n (%)

185 (8.6%)

261 (12.1%)

340 (15.8%)

499 (23.2%)

 < 0.001^b

Hypertension, n (%)

698 (32.5%)

760 (35.4%)

947 (44.1%)

1047 (48.7%)

 < 0.001^b

Kidney disease, n (%)

123 (5.7%)

132 (6.1%)

123 (5.7%)

115 (5.3%)

0.740^b

Heart disease, n (%)

188 (8.7%)

207 (9.6%)

274 (12.8%)

323 (15.0%)

 < 0.001^b

HbA1c (%), mean ± SD

5.15 ± 0.62

5.21 ± 0.71

5.27 ± 0.82

5.40 ± 0.96

 < 0.001^a

CRP (mg/l), median (IQR)

0.76 (0.45, 1.74)

0.89 (0.51, 1.87)

1.08 (0.58, 2.20)

1.32 (0.72, 2.68)

 < 0.001^c

eGFR, ml/min/1.73 m², median (IQR)

70.77 (52.33, 91.69)

72.38 (51.98, 94.43)

72.87 (53.67, 95.91)

76.17 (56.72, 100.74)

 < 0.001^c

BMI(kg/m²), mean ± SD

21.86 ± 3.13

22.77 ± 3.40

23.92 ± 3.58

25.00 ± 3.55

 < 0.001^a

TG (mg/dl), median (IQR)

61.06 (52.22, 71.68)

88.50 (77.00, 101.78)

123.01 (106.20, 140.71)

195.59 (161.07, 244.26)

 < 0.001^c

HDL-C, mean ± SD

67.08 ± 13.54

54.65 ± 10.20

47.27 ± 8.54

38.05 ± 7.99

 < 0.001^a

AIP, median (IQR)

− 0.03 (− 0.24, 0.13)

0.50 (0.38, 0.62)

0.96 (0.84, 1.09)

1.59 (1.39, 1.91)

 < 0.001^c