Clinical heterogeneity of Alzheimer's disease according to the age of onset

Introduction. The age of onset of Alzheimer's disease (AD) has been linked to the degree of clinical heterogeneity. Some studies have suggested that the presenile and senile forms may be different conditions. Aim. To describe the clinical and developmental characteristics of patients with AD according to the age of onset. Patients and methods. A clinical sample of AD patients was evaluated by means of the Cambridge Examination for Mental Disorders of the Elderly protocol together with other tests and clinical scales (Trail Making Test, Neuropsychiatric Inventory, Rapid-Disability Rating Scale-2 and Zarit Burden Interview). Patients were reassessed at 12 months. Results. Of the 492 participants, 419 (85.2%) were cases of late-onset AD and 73 cases (14.8%) had early-onset AD. For this latter group, the time between onset of the first symptoms and diagnosis of the disease was higher (3.85 versus 2.5 years) and there was a higher frequency of family histories of dementia (35.6%) and personal histories of psychiatric disorders (13.7%). This group also presented better scores on the functional evaluation scales and on the neuropsychological tests, as well as more frequent and severe symptoms of depression. At 12 months no clinical differences were recorded between the two groups, except for an increase in the firequency and severity of apathy. Conclusions. From the differences found between early-onset and late-onset AD we cannot consider them to be two different conditions from the clinical and/or neuropsychological point of view.