Cognitive state of the four groups.

P<0.05 is significant. MMSE total: total score of Mini-Mental state examination; CFT-Copy: copy part of complex figure test; CFT-Recall: recall part of complex figure test; AVLT-I: immediately recall of auditory verbal learning test; AVLT-II: delayed recall of auditory verbal learning test; AFT: animal fluency test; STT-A: part A of shape trails test; STT-B: part B of shape trails test; CDR: clinical dementia rating scale; CDR-SB: clinical dementia rating scale Sum of Boxes.