Sex differences in cognition in healthy elderly individuals.

Sex differences in patterns of cognitive test performance have been attributed to factors, such as sex hormones or sexual dimorphisms in brain structure, that change with normal aging. The current study examined sex differences in patterns of cognitive test performance in healthy elderly individuals. Cognitive test scores of 957 men and women (age 67-89), matched for overall level of cognitive test performance, age, education, and depression scale score, were compared. Men and women were indistinguishable on tests of auditory divided attention, category fluency, and executive functioning. In contrast, women performed better than men on tests of psychomotor speed and verbal learning and memory, whereas men outperformed women on tests of visuoconstruction and visual perception. Our finding that the pattern of sex differences in cognition observed in young adults is observed in old age has implications for future studies of both healthy elderly individuals and of those with cognitive disorders.

Neuroanatomic and cognitive abnormalities related to herpes simplex virus type 1 in schizophrenia.

Herpes simplex virus 1 (HSV-1) tends to replicate in the temporal cortex and can damage the limbic system. The presence of serum antibodies to HSV-1 is associated with cognitive impairment in adults with schizophrenia, suggesting that cerebral gray matter abnormalities might distinguish patient subgroups defined by HSV-1 exposure. We assessed 43 adult outpatients with schizophrenia. The assessment included clinical interviews, neurocognitive testing, anatomic brain magnetic resonance imaging and measures of serum IgG antibodies specific to herpes simplex viruses 1 and 2. We then compared 25 patients who tested positive for antibodies to HSV-1 with 15 who were seronegative for both HSV-1 and HSV-2. The seropositive patients performed significantly worse than the seronegative patients on four neuropsychological measures of psychomotor speed, executive functioning, and explicit verbal memory. Voxel-based morphometric analyses revealed that the same patients showed reduced gray matter volume in the anterior cingulate and areas of the cerebellum. Finally, performance on the test of psychomotor speed and executive functioning that showed the largest between- group effect size correlated with reduced gray matter volume in some of the same brain regions (cingulate and cerebellum) that distinguished the two HSV-1 subgroups. In these outpatients with schizophrenia, HSV-1 seropositivity and performance on a cognitive test that is highly sensitive to it co-localize to closely overlapping brain regions.

Accounting for estimated IQ in neuropsychological test performance with regression-based techniques.

Regression-based normative techniques account for variability in test performance associated with multiple predictor variables and generate expected scores based on algebraic equations. Using this approach, we show that estimated IQ, based on oral word reading, accounts for 1-9% of the variability beyond that explained by individual differences in age, sex, race, and years of education for most cognitive measures. These results confirm that adding estimated "premorbid" IQ to demographic predictors in multiple regression models can incrementally improve the accuracy with which regression-based norms (RBNs) benchmark expected neuropsychological test performance in healthy adults. It remains to be seen whether the incremental variance in test performance explained by estimated "premorbid" IQ translates to improved diagnostic accuracy in patient samples. We describe these methods, and illustrate the step-by-step application of RBNs with two cases. We also discuss the rationale, assumptions, and caveats of this approach. More broadly, we note that adjusting test scores for age and other characteristics might actually decrease the accuracy with which test performance predicts absolute criteria, such as the ability to drive or live independently.

Development, psychometric properties, and validity of the hopkins adult reading test (HART).

We describe the development of a 35-item, oral word-reading test with two equivalent forms (HART-A and HART-B) designed to estimate premorbid abilities. Both forms show excellent internal consistency (coefficients alpha>.91) and test-retest reliability (Pearson rs >.90). HART performance was combined with demographic variables to generate regression equations that predict IQ scores obtained concurrently and 4-8 years earlier. The resulting models explained 61% of full scale IQ (FSIQ) variability in 327 healthy adults. The FSIQs that can be estimated range from below 73 to above 131. Combined with demographic variables, these two brief word reading tests accurately predict a broader range of IQs than Blair and Spreen's (1989) longer version. Equivalent forms make it especially useful for longitudinal studies.

Frequency and bases of abnormal performance by healthy adults on neuropsychological testing.

The frequency and determinants of abnormal test performance by normal individuals are critically important to clinical inference. Here we compare two approaches to predicting rates of abnormal test performance among healthy individuals with the rates actually shown by 327 neurologically normal adults aged 18-92 years. We counted how many participants produced abnormal scores, defined by three different cutoffs with test batteries of varied length, and the number of abnormal scores they produced. Observed rates generally were closer to predictions based on a series of Monte Carlo simulations than on the binomial model. They increased with the number of tests administered, decreased as more stringent cutoffs were used to identify abnormality, varied with the degree of correlation among test scores, and depended on individual differences in age, education, race, sex, and estimated premorbid IQ. Adjusting scores for demographic variables and premorbid IQ did not reduce rates of abnormal performance. However, it eliminated the contribution of these variables to rates of abnormal test performance. These findings raise fundamental questions about the nature and interpretation of abnormal test performance by normal, healthy adults.