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Table 3 The final three-group trajectory model of global cognitive scores as function of age in middle-aged and older adults from CHARLS

From: Associations between social and intellectual activities with cognitive trajectories in Chinese middle-aged and older adults: a nationally representative cohort study

Trajectory group

Parameter

Maximum likelihood estimates

Est.

SE

z value

p value

Class 1: persistently low cognitive function (n = 1550, 18.9%)

Intercept

− 5.04

1.21

− 4.157

< 0.001

Linear (age)

1.38

0.38

3.592

< 0.001

Quadratic (age2)

− 0.13

0.03

− 4.201

< 0.001

Class 2: persistently moderate cognitive function (n = 3194, 38.9%)

Intercept

− 6.02

0.98

− 6.153

< 0.001

Linear (age)

2.05

0.31

6.615

< 0.001

Quadratic (age2)

− 0.18

0.03

− 7.308

< 0.001

Class 3: persistently high cognitive function (n = 3460, 42.2%)

Intercept

11.35

6.13

1.853

0.064

Linear (age)

− 5.26

2.93

− 1.795

0.073

Quadratic (age2)

0.89

0.46

1.928

0.054

Cubic (age3)

− 0.05

0.02

− 2.109

0.035

  1. CHARLS China Health and Retirement Longitudinal Study, Est. parameter estimate, SE standard error of parameter estimate