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Thirty-one patients with Alzheimer disease (AD) and 26 patients with Huntington disease (HD) were assessed using new scales to measure apathy and irritability. An existing scale was used to assess aggression. A similar prevalence of apathy and irritability was found in the two groups. The HD patients were more aggressive than the AD patients. In a subsample of the two groups, matched for degree of cognitive impairment, the HD patients were found to be more apathetic than the AD group. Irritability was related to be the premorbid trait of "bad temper" in HD but not in AD. There was no interrelationship among the three symptoms in either group. The scales for irritability and apathy have both interrater and test-retest reliability. They are able to differentiate patients with AD and HD from normal, disease-free control subjects. The usefulness of these scales, in relation to preexisting scales, is discussed.
Burns et al. (Mon,) studied this question.