Limitations
Alzheimer’s disease, cognitive decline, MCI, neurodegenerative disease
DISEASE, SECONDARY, NEURODEGENERATIVE DISEASE
The study has several limitations. First, the sample sizes were relatively small due to the strict selection criteria set for the study. The small sample sizes, in particular, were among those showing test score changes above the MCID thresholds for the between-group comparisons. This could have lowered the power of the analyses, causing an underestimation of the effects of the CCT on SC-FC coupling and nodal topography. Second, corrections for the multiple comparisons and correlational analyses were not applied to selected secondary outcome variables. Readers are reminded to take caution when interpreting the findings on brain network parameter changes and their relationships with improvements in CCT-related cognitive functions. Future studies should consider setting specific a priori hypotheses on testing the brain network to behavioral relationships related to CCT. Third, individuals with MCI are heterogeneous. The inclusion criteria do not stipulate the disease process behind cognitive decline, such as early neurodegenerative disease or Alzheimer’s disease. The readers are reminded to be cautious with generalizing the results of the CCT effects to MCI individuals with specific pathologies. Fourth, because of the lack of a follow-up design, the long-lasting effect of the CCT remains to be explored in future studies. Another limitation is the possible learning effects developed among the participants due to the use of the same neuropsychological tests as the outcome measures. Although the learning effects, if any, would have been accounted for by the experimental-control group design, future studies should consider conducting pre- and post-training testing with instruments having parallel or alternate forms.