Differences between Early and Late-Onset Alzheimer’s Disease in Neuropsychological Tests

Abstract

Although patients with Alzheimer disease (AD) share clinical and histological features regardless of age of onset, the hypothesis that early onset AD constitutes a distinct subgroup prevails. Some authors suggest that early attention or language impairment constitute patterns of differentiation in terms of neuropsychological profile, between these groups. However, investigations are not consensual in terms of cognitive domains affected in each group. Aim: To investigate whether there is early neuropsychological difference between two types of AD using the conventional dividing line of 65 years. Methods: We evaluated the results obtained in the Mini-Mental State Examination (MMSE) and in a comprehensive neuropsychological battery – Battery of Lisbon for the Assessment of Dementia (BLAD), at a Dementia clinic in the University Hospital of Coimbra and a Memory Clinic. The study was developed in consecutive patients with a clinical probable diagnosis of mild to moderate AD, using standard criteria (DSMIV and NINCDS-ADRDA). Statistical analysis was performed using Qui-square and U-Mann–Whitney, for categorical and non-categorical variables. The degree of relation between variables, was measured using the coefficient of correlation rs de Spearman. Results: The total sample included 280 patients: 109 with early onset AD and 171 with a late-onset form. Groups were comparable in terms of gender, education or severity of disease, and MMSE. In BLAD, for univariate analysis the early onset group had lower scores in Naming (p = 0.025), Right–Left Orientation (p = 0.029) and Praxis (p = 0.001), and better performances in Orientation (p = 0.001) and Visual Memory (p = 0.022). After application of Bonferroni correction for multiple comparisons only Praxis and Orientation could differentiate the two groups. No significant differences were found in other tests or functions. Discussion: The results are suggestive of dissociated profiles between early and late-onset AD. Younger patients have a major impairment in Praxis and a tendency for a great impairment in neocortical temporal functions. AD patients with late-onset forms had a tendency for worse performances in Visual Memory and Orientation, suggesting a more localized disease to the limbic structures.

Differentiated clinical presentation of early and late-onset Alzheimer’s disease: is 65 years of age providing a reliable threshold?

“…Other studies have also found a differentiated cognitive profile in the initial presentation of AD according to age of onset [9,[18][19][20]. However, there are some contradictory results [21,22] and there is no current consensus about which cognitive domains are more impaired in each group.…”

“…As in previous studies, age at symptom onset (estimated as reported by family member and/or caregiver) was used to classify patients in EOAD and LOAD groups [5, 7, 10-12, 16, 17, 19, 22, 30]. A standardized interview was used to maximize the reliability establishing the age of onset, as in former research [19,21,33]. The caregiver was asked to identify the ''first problem'' in a structured interview and to give a detailed narrative about it, to further identify the ''earliest episode'' dated by referencing it to a calendar date.…”

Apraxia in Mild Cognitive Impairment and Alzheimer's Disease: Validity and Reliability of the Van Heugten Test for Apraxia

“…The few former studies of apraxia in AD mostly included small patient samples, and sometimes tests were not well validated [10,11,12,30,31,32]. One of the major issues of some of the earlier studies is that it is hard to replicate them because it is unknown how or which test was used to assess praxis [12]. Furthermore, in some cases the tests used to measure deficits in praxis seem more likely to measure executive functioning and visuoconstruction [30].…”

“…Another small study in AD patients and healthy controls showed that patients performed worse on both ideomotor and ideational apraxia than controls, and especially pantomimes of tool use were most impaired [11]. Furthermore, it has been suggested that patients with early-onset AD were more impaired on praxis than late-onset patients [12]. As can be seen in table 1, tests were not validated.…”

“…As can be seen in table 1, tests were not validated. Moreover, the test that was used was often not described in detail [12]. …”