Tapping into the biology of Alzheimer disease

Cognitive reserve moderates relation between global cognition and functional status in older adults

The ability to perform instrumental activities of daily living (IADLs) is necessary for independent living. Research suggests that community-dwelling older adults are at risk for experiencing subtle decrements in the performance of IADLs. Neuropsychological tests have been used to account for differences in IADL status. Studies of the relationship between cognitive ability and functional status have produced variable results, however, and cognitive ability appears to be only a moderate predictor. Several studies of normal aging have revealed cognitive and functional benefits of higher cognitive reserve (CR) in healthy, nondemented older adults. The purposes of the present study were to: (a) examine the relationship between global cognitive ability and IADL performance among 53 community-dwelling older adults, and (b) determine whether formal education, as a proxy of CR, significantly moderates this relationship. Consistent with previous findings, global cognitive ability accounted for a considerable portion of variance in IADL performance [ΔR(2) = .54; ΔF(2, 53) = 67.96; p < .001]. Additionally, CR modestly but significantly attenuated this relationship [ΔR(2) = .044; ΔF(4, 53) = 5.98; p = .018; total R(2) = .65]. This finding suggests that community-dwelling older adults with lower levels of formal education may be at greater risk for functional decrements associated with age-related cognitive decline.

Idea density measured in late life predicts subsequent cognitive trajectories: implications for the measurement of cognitive reserve

OBJECTIVE

The Nun Study showed that lower linguistic ability in young adulthood, measured by idea density (ID), increased the risk of dementia in late life. The present study examined whether ID measured in late life continues to predict the trajectory of cognitive change.

METHOD

ID was measured in 81 older adults who were followed longitudinally for an average of 4.3 years. Changes in global cognition and 4 specific neuropsychological domains (episodic memory, semantic memory, spatial abilities, and executive function) were examined as outcomes. Separate random effects models tested the effect of ID on longitudinal change in outcomes, adjusted for age and education.

RESULTS

Lower ID was associated with greater subsequent decline in global cognition, semantic memory, episodic memory, and spatial abilities. When analysis was restricted to only participants without dementia at the time ID was collected, results were similar.

DISCUSSION

Linguistic ability in young adulthood, as measured by ID, has been previously proposed as an index of neurocognitive development and/or cognitive reserve. The present study provides evidence that even when ID is measured in old age, it continues to be associated with subsequent cognitive decline and as such may continue to provide a marker of cognitive reserve.

Diagnosis of Alzheimer's disease in Brazil: Supplementary exams

This article presents a review of the recommendations on supplementary exams employed for the clinical diagnosis of Alzheimer's disease (AD) in Brazil published in 2005. A systematic assessment of the consensus reached in other countries, and of articles on AD diagnosis in Brazil available on the PUBMED and LILACS medical databases, was carried out. Recommended laboratory exams included complete blood count, serum creatinine, thyroid stimulating hormone (TSH), albumin, hepatic enzymes, Vitamin B12, folic acid, calcium, serological reactions for syphilis and serology for HIV in patients aged younger than 60 years with atypical clinical signs or suggestive symptoms. Structural neuroimaging, computed tomography or - preferably - magnetic resonance exams, are indicated for diagnostic investigation of dementia syndrome to rule out secondary etiologies. Functional neuroimaging exams (SPECT and PET), when available, increase diagnostic reliability and assist in the differential diagnosis of other types of dementia. The cerebrospinal fluid exam is indicated in cases of pre-senile onset dementia with atypical clinical presentation or course, for communicant hydrocephaly, and suspected inflammatory, infectious or prion disease of the central nervous system. Routine electroencephalograms aid the differential diagnosis of dementia syndrome with other conditions which impair cognitive functioning. Genotyping of apolipoprotein E or other susceptibility polymorphisms is not recommended for diagnostic purposes or for assessing the risk of developing the disease. Biomarkers related to the molecular alterations in AD are largely limited to use exclusively in research protocols, but when available can contribute to improving the accuracy of diagnosis of the disease.