Early Markers Of Alzheimer Disease

Aging

Investigators

Linked publications & trials

Abstract

Alzheimer's disease (AD) is the most widespread among several neurological degenerative diseases (dementias) that occur principally at later ages, occasionally before 60, but more frequently after age 70. This study examines prospective psychological, neurological, and neuropsychological changes in participants from the Baltimore Longitudinal Study of Aging (BLSA). Neurological and neuropsychological examinations are administered to participants aged 60 and older, repeating many of the tests that were administered to these subjects at earlier ages. Diagnoses of probable Alzheimer's disease follow the NINCDS-ADRDA criteria. In addition, this study examines the role of depression and depressive symptoms. These conditions are involved in as many as half of dementia cases, particularly in the early cases. Although it is unclear whether depression is uniformly prodromal or a risk factor, it is important to understand the time course of depressive symptoms and its association with cognitive decline and dementia.[unreadable] [unreadable] Vascular dementia is considered second only to AD as a cause of dementia in population-based epidemiological studies of the incidence and prevalence of dementia. Most studies indicate that AD type pathology and vascular disease make independent contributions to the diagnoses of dementia. Because vascular and AD pathology coexist in the brains of many elderly subjects, it has been challenging to examine the unique contribution of each process to the clinical picture of dementia. Section investigators examined the effect of clinically overt stroke on the risk of dementia using clinical data from the Baltimore Longitudinal Study of Aging (BLSA) Autopsy Program, a prospective study of the effects of normal aging in community-dwelling volunteers who have agreed to autopsy following death. We examined the effect of a clinically detectable stroke on the risk of dementia using prospective data from 335 BLSA participants. Clinically overt strokes are common in our cohort (cumulative risk by age 90 15.4%; 95% CI 10-22%) and confer a significant risk for dementia compared to subjects without stroke (OR = 5.55; 95% CI 2.76-11.4). The size of the stroke, measured by the post-stroke clinical deficit, was not different in the group who subsequently became demented from that in the group with stroke who did not. The majority of participants who became demented after a stroke had evidence of mild cognitive impairment preceding the stroke (14 of 19). Moreover, a clinically symptomatic stroke was a major risk factor for the conversion of mild cognitive impairment to dementia (OR 12.4; 95% C.I. 1.5 ? 99). When cognitive impairment did not precede the stroke, there was no increase in the risk of subsequent dementia. A history of other atherosclerotic diseases in the absence of stroke did not contribute to dementia. These data suggest that dementia after stroke is often determined by cognitive impairment that existeed prior to the stroke.[unreadable] [unreadable] In a separate study, section investigators examined cross-sectional and longitudinal age and sex differences in each of the Center for Epidemiological Studies Depression Scale's 4 subscales of depressive symptomatology. Two independent studies (Sample 1 = 2,076; Sample 2 = 943) were used for purposes of establishing stability of findings. Sample 1 was derived from the National Health and Nutrition Survey baseline and follow-up study in which a nationally representative sample of 1,167 women and 909 men were examined over 6-10 years. Sample 2 was derived from the BLSA in which 400 women and 543 men were examined over 8 years. Results indicate a reasonable degree of stability among adults under 70 years of age. However, there were significant age-related increases in somatic symptoms and lack of well-being after approximately 70 years of age, whereas symptoms related to depressed affect and interpersonal problems remained stable. Notably, depressive affect symptoms remained stable given significant age-related somatic changes. The addition of comorbid physical illness to the analysis did not reduce the association between age and depressive symptoms, indicating that part of the association was not substantially accounted for by physical health.