Introduction: Visual episodic memory is affected in the early phases of Alzheimer's disease (AD).
Aims: To design a visual memory test free of any verbal content, to offer its normative values in the elderly population in Spain, to validate the test in a group of patients with mild AD and to determine its capacity to discriminate between subjects with AD and controls.
Subjects and methods: The study involved a sample of 263 subjects (137 controls and 126 patients with AD) over 50 years of age. The landscape test consists of a first part in which participants are shown 25 photographs of landscapes. Five minutes later, the previous 25 photos are shown again together with 25 new pictures, and the subject must recognise the ones that have already been seen. The statistical analysis was performed using the Student t test for independent measures, ANCOVA, linear regression, Pearson's correlation and the ROC curve.
Results: In the control group, sex and schooling did not have any significant effect on the results, although differences were found between the youngest group (50-59 years) and the oldest age group (equal to or above 80 years). Findings show that there is a significant difference between the mean scores on the landscape test obtained by the two groups (control: 44.06 ± 3.2; AD: 34.25 ± 6.6; p < 0.001). The area under the curve from the landscape test was 0.904, with a sensitivity of 0.82 and a specificity of 0.85.
Conclusions: The landscapes test is a simple, sensitive and novel instrument for assessing visual memory in early AD.