Two measures of social function designed for community studies of normal aging and mild senile dementia were evaluated in 195 older adults who underwent neurological, cognitive, and affective assessment. An examining and a reviewing neurologist and a neurologically trained nurse independently rated each on a Scale of Functional Capacity. Interrater reliability was high (examining vs. reviewing neurologist, r = .97; examining neurologist vs. nurse, tau b = .802; p less than .001 for both comparisons). Estimates correlated well with an established measure of social function and with results of cognitive tests. Alternate informants evaluated participants on the Functional Activities Questionnaire and the Instrumental Activities of Daily Living Scale. The Functional Activities Questionnaire was superior to the Instrumental Activities of Daily scores. Used alone as a diagnostic tool, the Functional Activities Questionnaire was more sensitive than distinguishing between normal and demented individuals.

In a white, predominantly middle class southern California retirement community, 817 adults aged 65-99 years were evaluated in 1980-1982 in a study designed to assess prevalence of early Alzheimer-type senile dementia. Based on 162 neurologically diagnosed cases, the age- and sex-adjusted prevalence of Alzheimer's disease in the target population was 15.3% (95% confidence interval = 13.0-17.5) among persons aged 65+ years and 35.8% among persons aged 80+ years. Age-adjusted correction for false negatives not detected by a screening procedure yields an estimated prevalence of 16.4% in persons aged 65+ years. Validity of the diagnostic approach was confirmed by a follow-up study. These rates far exceed past prevalence estimates for this disease. Since prevalence of mid- or later stages of Alzheimer's disease may have been underestimated, the high rates in this study may reflect a considerable community burden of early disease. Observed prevalence of Alzheimer-type senile dementia was higher among men than women after adjustment for age, 19.1% and 13.1%, respectively. The female predominance reported in many past clinical surveys may be peculiar to late disease and reflect care-seeking and care-utilization behaviors, rather than differences in incidence.

To validate a senile dementia survey diagnostic tool, 195 individuals aged 61-91 and referred by their physicians as normal or mildly demented were examined. The etiologic diagnosis used as criterion was the consensus of two experienced neurologists, assisted by clinical and laboratory data from referring physicians and by neuropsychologic evaluation of questionably affected persons. Agreement between the neurologists was high, as indicated by a weighted Kappa coefficient of 0.97 (95% confidence interval (Cl) (0.94, 1.00)). Agreement between the instrument and criterion diagnosis was also excellent (kappa w = 0.93; 95% Cl (0.88, 0.98)). Used alone as a screening diagnostic tool, the cognitive function portion of the instrument was much more sensitive (0.929) than previously used brief tests and was acceptably specific (0.800). Because normals complete this cognitive test in 15-20 minutes, it should be a major advance in population-based studies of senile dementia and normal aging.

The Mental Function Index is a weighted combination of scores on three brief tests. The Index was developed to aid in the discrimination of elderly persons with early cases of senile dementia from nondemented elderly individuals. In a previous report (Am J Epidemiol 1981;114:515-27), the authors described preliminary results with the Index in 195 elderly persons in a southern California retirement community. The present study seeks to assess whether similar results can be achieved in samples other than that from which the discriminant function defining the Index was derived. Seven separate studies were done on a total of 210 persons, comprising subjects recruited from a teaching hospital which serves a predominantly lower to lower-middle class population, referrals from the same physicians as in the earlier study, and (for the reliability sample) persons from the upper-middle class community which was the major referral source. It was found that scores on the brief measures correlate 0.86 with those on the three Halstead-Reitan subtests most sensitive to brain damage and to aging. The Index provides a graded measure of disease severity comparable to global neurologic assessment (r = -0.84) and level of social function (r = 0.76). Entry Index is a crude predictor of cognitive status in older adults after several years. Changes in the Index over time parallel those in independent measures of change. The results suggest that the Index will be useful for assessment of disease severity and of longitudinal change, as well as for diagnostic screening, in population studies of senile dementia.

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