General intellectual decline and daily living skills.

A total of 64 elderly individuals presenting with cognitive decline were administered a test of general intelligence and a measure of adaptive knowledge and daily living skills. Premorbid ability was estimated using a demographic formula and a reading test. After controlling for age and depression, general intellectual ability accounted for a large amount of the variance in a broad range of adaptive knowledge and behavioral skills, reflecting the influence of premorbid ability and especially estimated decline. Different patterns of adaptive knowledge and skills were identified as a function of measured IQ and of estimated decline in IQ. Results suggest a threshold of intellectual decline for deterioration in daily living skills. Studies purporting to demonstrate that impairments in particular neuropsychological domains predict specific functional deficits need to control for general intellectual ability and/or the extent of intellectual decline.