White matter integrity of default mode network after a 3-month aerobic dance program in patients with amnestic mild cognitive impairment: a secondary analysis of a randomized clinical trial.

Abstract

Background: Exercise is an effective non-pharmacological strategy to enhance cognitive function in individuals with mild cognitive impairment (MCI). Our previous studies confirmed that aerobic dance can increase the amplitude of low-frequency fluctuations (LFF) in bilateral fronto-temporal, entorhinal, anterior cingulate, and para-hippocampal cortices. However, its effects on structural connections remain unclear. The present study comprised a secondary analysis of a randomized clinical trial and aimed to examine the impact of a 3-month aerobic dance program on white matter integrity of default mode network (DMN) in older adults with amnestic MCI, as assessed by magnetic resonance imaging (MRI).

Methods: A total of 112 patients with memory decline were recruited, 38 of whom completed cognitive assessments and magnetic resonance scans and were randomized to the exercise group (n=19) or the control group (n=19). The exercise group received 3 months of aerobic dance and health education, whereas the control group only received health education. All participants underwent cognitive assessments and MRI scans at baseline and after the 3-month intervention. A series of neuropsychological assessments, including Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Wechsler Memory Scale-Revised Logical Memory (WMS-RLM), Trail Making Test Part A&B (TMT-A&B), Symbol Digit Modalities Test (SDMT), and Forward and Backward Digit Span Task (DST) Chinese version, were used to assess the participants' global cognitive function, memory function, and executive function. Structural connections of the hippocampus-hub temporal network were analyzed using the network-based statistic.

Results: Finally, 16 participants in each group were included in the statistics and analysis. There was no statistical difference in cognitive functions at 3 months in the control group compared with those at baseline. However, the cognitive functions of the exercise group improved significantly after 3 months of aerobic dance, including MMSE (P=0.006), MoCA (P=0.009), WMS-RLM (P=0.005), TMT-A (P=0.007), and DST (P=0.025). Moreover, the exercise group had significantly improved WMS-RLM (P=0.003) compared to the control group after 3 months of intervention. In addition, they showed significant increases in structural connections within the DMN, including the structural connection between hippocampus and para-hippocampus, hippocampus and fusiform gyrus, hippocampus and middle temporal gyrus, and precuneus and middle temporal gyrus. The structural connection between DMN and supplementary motor area was also significantly increased in the exercise group, correlating positively with MMSE (R=0.31, P=0.04) and negatively with TMT-A (R=-0.40, P=0.011), respectively.

Conclusions: A 3-month aerobic dance program may enhance the structural connections in the hippocampus-hub temporal network and improve episodic memory and global cognition in older adults with amnestic MCI.