Subjective memory impairment (SMI) is common among older adults. Increasing evidence suggests that SMI is a risk factor for future cognitive decline, as well as for mild cognitive impairment and dementia. Medial temporal lobe structures, including the hippocampus and entorhinal cortex, are affected in the early stages of Alzheimer's disease. The current study examined the gray matter (GM) volume and microstructural changes of hippocampal and entorhinal regions in individuals with SMI, compared with elderly control participants without memory complaints.

A total of 45 participants (mean age: 70.31 ± 6.07 years) took part in the study, including 18 participants with SMI and 27 elderly controls without memory complaints. We compared the GM volume and diffusion tensor imaging (DTI) measures in the hippocampal and entorhinal regions between SMI and control groups.

Individuals with SMI had lower entorhinal cortical volumes than control participants, but no differences in hippocampal volume were found between groups. In addition, SMI patients exhibited DTI changes (lower fractional anisotropy (FA) and higher mean diffusivity in SMI) in the hippocampal body and entorhinal white matter compared with controls. Combining entorhinal cortical volume and FA in the hippocampal body improved the accuracy of classification between SMI and control groups.

These findings suggest that the entorhinal region exhibits macrostructural as well as microstructural changes in individuals with SMI, whereas the hippocampus exhibits only microstructural alterations.

Cerebral white matter hyperintensities (WMH) are prevalent incident findings on brain MRI scans among elderly people and have been consistently implicated in cognitive dysfunction. However, differential roles of WMH by region in cognitive function are still unclear. The aim of this study was to ascertain the differential role of regional WMH in predicting progression from mild cognitive impairment (MCI) to different subtypes of dementia.

Participants were recruited from the Clinical Research Center for Dementia of South Korea (CREDOS) study. A total of 622 participants with MCI diagnoses at baseline and follow-up evaluations were included for the analysis. Initial MRI scans were rated for WMH on a visual rating scale developed for the CREDOS. Differential effects of regional WMH in predicting incident dementia were evaluated using the Cox proportional hazards model.

Of the 622 participants with MCI at baseline, 139 patients (22.3%) converted to all-cause dementia over a median of 14.3 (range 6.0–36.5) months. Severe periventricular WMH (PWMH) predicted incident all-cause dementia (Hazard ratio (HR) 2.22; 95% confidence interval (CI) 1.43–3.43) and Alzheimer's disease (AD) (HR 1.86; 95% CI 1.12–3.07). Subcortical vascular dementia (SVD) was predicted by both PWMH (HR 16.14; 95% CI 1.97–132.06) and DWMH (HR 8.77; 95% CI 1.77–43.49) in more severe form (≥ 10 mm).

WMH differentially predict dementia by region and severity. Our findings suggest that PWMH may play an independent role in the pathogenesis of dementia, especially in AD.