Memory profile in different subtypes of Alzheimer’s disease based on patterns of regional brain atrophy
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Introduction: An explanation for the worldwide struggle to find a cure for Alzheimer’s disease (AD) might be the underlying biological heterogeneity of the disease. In order to better understand differences in clinical manifestations that are seen in AD patients, this research focused on subtyping AD patients based on structural brain atrophy patterns and subsequently studying their corresponding memory profile. Methods: A population reference group (n = 27) was recruited and used for studying relationships between memory components in a population based group. A number of 229 healthy controls and 192 AD patients from ADNI were included to investigate relationships between memory, other cognitive functions and brain atrophy patterns in AD. Results: Three AD subtypes were identified based on atrophy in the medial temporal lobe alone (MTA), together with other brain regions (MTA+), or sparing of the medial temporal lobe (non-MTA). All memory components were impaired in the AD-subtypes compared to healthy controls. Learning and recognition was modulated by the AD subtype. The MTA+ subtype was the subtype showing worse memory profile. The non-MTA group benefited the most from external help in retrievement of learnt information. Influence of other cognitive functions on memory was different in the AD subtypes as compared to the healthy controls, showing loss of specificity and disruption of normal cognitive support in AD. Conclusions: AD is heterogeneous and different forms of memory impairment are associated with different patterns of brain atrophy. Future research should focus on validating the categorized groups from this research by including more (biological) variables and clinical qualitative information, as well as investigating of longitudinal trajectories of the different AD subtypes.