We found that the LLD + CVC group had the lowest recall memory scores of the four groups. This indicated that depression might affect memory more than it affects the other functions tested by the MMSE, which might be used for preliminary screening of the older elderly. Kramer-Ginsberg et al.
 found no significant differences in the Animal Naming tests (executive domain) or in the General Memory index of the revised Wechsler Memory Scale, but a significantly lower score was found in the Delayed Recall index, which was similar to our finding. This might imply that the depressed older elderly could have moderate-to-severe deep white matter MRI signal hyperintensities, which indicate perivascular lesions caused by 'dilated perivascular spaces (with and without ischemia in the perivascular area), oligemic demyelination, [or] ischemic demyelination’
. Regular follow-ups are necessary to search for additional organic and structural changes, such as Parkinson's disease, dementia, and other neurodegenerative diseases, in the brains of the depressed older elderly.
The LLD + CVC group had the lowest executive function scores of the four groups, which is consistent with previous reports
. There were no significant differences between the CVC and the LLD groups or the LLD and the LLD + CVC groups, but there were significant differences between the CVC and the LLD + CVC groups for most of the tested indices. This implied that LLD has a far more important effect on neurocognitive impairment than do CVCs in the older elderly.
The explanation for the nonsignificant differences between the LLD and LLD + CVC groups might be a similar pathogenesis of depression and cardiovascular comorbidities, such as neuroendocrine dysfunctions, inflammatory processes, autonomic dysregulation, platelet abnormalities, and certain vulnerability genes
, all of which may lead to cognitive deficits
 and to a cumulative effect of a comorbidity on the degree of cognitive deficit
Although we found no significant differences between the CVC and the LLD groups in the MMSE testing, we did find significant differences between their scores on the WCST and the TMT. On the WCST, the LLD group had significantly lower scores than did the CVC group, but on the TMT, the CVC group took a significantly longer time to complete the task. This suggests that LLD and CVC have different neurocognitive effects in the older elderly. Although both tools are used to examine executive function in general, some differences between them should be taken into account. The TMT tests psychomotor performance and the WCST tests reasoning. Planning might be more affected by cardiovascular comorbidities than by depression. Moreover, the CVC group might have mild but asymptomatic cardiovascular comorbidities such as atrial fibrillation, which could affect executive function and psychomotor tasks. Even in the absence of manifest stroke, atrial fibrillation is a risk factor for memory impairment and hippocampal atrophy
In the older elderly, negative moods, feelings of inferiority, and disinterest seem to have an important effect on neurocognitive performance, one that is associated primarily with psychomotor retardation rather than with other cognitive functions. That the LLD group patients in this study were much slower than the CVC group patients was probably because of their depression
. In addition, looking into the questions of this subscale, all questions are about satisfaction with the quality of the respondent's quality of life (QoL) (satisfied with my current life, often feel bored, often feel lonely, often afraid unlucky things will happen, feel unhappy most of the time, and feel unhappy being alive). This correlation might reflect the evidence that the older elderly group who live without relatives would experience greater impact on their cognitive performance, especially those with depression. No association between LLD and GDS scores on the energy level was found, possibly because both aging and depression lower their energy and this index of GDS may not be as sensitive in distinguishing the effect between aging and depression in the older elderly. Although a negative correlation was found between TMT (B/A) and GDS in the disinterest level, this might reflect a curvilinear correlation with cerebral impairment, as Corrigan and Hinkeldey
 suggested. They also reported that TMT (B/A) was more sensitive than TMT (B-A) in differentiating lateralized damage but may not relate to impairment. The negative association between the inferiority subitem and the TMT-B score might reflect that these veterans may need more attention from more different people, not just the caregivers they see every day in the hospital, but less attention related to their actual cognitive impairment. In addition, the patients' energy levels could be affected by their QoL
; moreover, the onset and duration of depression might have another effect and requires further study.
The findings of this study may give psychiatric clinicians and primary care physicians an indication that mood and self-esteem should be taken into account while caring for the older elderly, whose memories are more vulnerable than those of the younger elderly to the adverse effects of negative emotional states
. In addition, most of the older elderly recruited in this study lacked family support and lived alone, which may have lowered their self-esteem and increased their negative emotions. Providing access to primary care institutions and other caregivers in a community-based program might be helpful for this older elderly group.
The findings of the present study might not be generalizable to other cohorts of older elderly because all of our participants were men. The older elderly should also be studied to see whether there are significant gender-based differences. Moreover, the small sample size in both the LLD and LLD + CVC groups might limit the applicability of the results for the effect of depression on memory in the older elderly. Using the MMSE as a screening instrument to make a diagnosis might also be a limitation. In addition, the variability of the cardiovascular comorbidities in the CVC group could affect different cognitive domains and limit the applicability of our conclusion. Further focusing on specific diseases is needed to clarify the effect of depression on the older elderly.