Objective: This study aimed to assess and characterize the heterogeneity of cognitive functioning in healthy elderly (HE) by focusing on age, education, beta-amyloid burden (AB), white matter hyperintensities (WMH), and cortical thickness.
Participants and Methods: 104 HE carried out a detailed neuropsychological assessment of processing speed, visual attention, visuospatial abilities, working memory, executive functions, episodic memory, semantic memory and language. AB was measured using PIB-PET, while cortical thickness and WMH were assessed using structural MRI. A hierarchical cluster analysis was carried out to determine the different patterns of cognitive performance. Performance of different groups was then examined using one-way ANOVAs.
Results: The cluster analysis revealed 4 cognitive profiles. The 1st group (19.6% of the sample) showed better performance in all cognitive domains (z-scores > 0.5 in all domains). The 2nd group (34% of the sample) showed average performance in most domains (z-scores between -0.12 and 0.6) but relatively weaker performance in episodic memory. The 3rd group (22.7% of the sample) showed low-average performance in most domains (z-score between -0.6 and 0.2) but was relatively better in episodic memory. The 4th (23.7% of the sample) showed the weakest cognitive performance overall (z-scores between -0.7 and -1.1). The four profiles differed in terms of age, AB burden and WMH, but did not differ in terms of education and cortical thickness. Participants in the 1st group were younger and had the least AB and WMH, while those in the 4th group were older and had the most AB and WMH burden.
Conclusions: Results of this study suggest that different patterns of cognitive decline occur in normal aging and that poorer cognition in various domains is associated with the presence of specific biomarkers such as AB and WMH. Future studies are required to disentangle the respective contributions of age and biomarkers on cognitive decline in HE.