There are estimated to be more than 18 million people world-wide suffering from dementia and, on entering the twenty-first century, demographic projections suggest that there will be a significant growth in elderly populations due to decreasing infant mortality, improved public health and safety, medical advances, better education and housing and increased service provision. These population shifts will predictably lead to a greater demand on medical and welfare services.

Despite the fact that a sizeable proportion of the elderly population will at some time develop cognitive problems, accurate diagnosis is difficult due to the multiple pathology involved in these impairments. With the introduction of pharmacological treatments for cognitive impairments, the emphasis on establishing if people are suffering from a dementing illness is crucial. Furthermore, patients who are categorized as ‘subclinical’ cases of cognitive impairment often have an underlying risk for further progression. Although all clinical definitions of dementia stress that there must be evidence of intellectual decline, the most common being memory failure, there is confusion surrounding the nature of cognitive deficits in the three most commonly applied criteria for dementia – The International Classification of Diseases (ICD-10), The Diagnostic and Statistical Manual for Mental Disorders (DSM–IV) and the National Institute of Neurological Disorders and Strokes (NINDS), Association Internationale pour le Recherche et l’Enseignement en Neurosciences (AIREN).