Clinical assessment of mental decline in elderly people: a proposal for a new quantitative index

Despite the many instruments available for assessing elderly people, there is a need for additional methods to measure mental decline that would also be applicable in cross sectional and longitudinal studies. With this purpose in mind, our group developed and checked a new instrument, the Index of Mental Decline (IMD), which consists of five clusters of items intended for the assessment of cognition, personal interrelationships, affective disorders, apathy and somatic complaints. To improve its consistency, all clusters and items were evaluated individually, according to their clinical impact. Three levels of symptom importance were determined: absent to very mild, mild to moderate, severe to very severe. Inter-rater reliability and test-retest reliability were demonstrated in a sample of 59 subjects, and proved to be satisfactory. The validity of the IMD was tested in a group of 203 patients, in whom a clinical diagnosis of probable dementia (DSM III-R criteria) had been formulated. The results suggest the effectiveness of the IMD both in quantifying mental decline and monitoring clinical symptoms. The IMD cannot be the first step of diagnostic procedure, but it can be useful for evaluating mental decline in elderly subjects with cognitive disorders. In longitudinal studies, the presence of the same caregiver or informant is compulsory.