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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