Fast track — ArticlesThe effect of social networks on the relation between Alzheimer's disease pathology and level of cognitive function in old people: a longitudinal cohort study
Introduction
Several clinicopathological studies over the past two decades have shown that many elderly people with extensive pathology of Alzheimer's disease do not clinically manifest cognitive impairment.1, 2, 3, 4 This ability to tolerate the pathology of this disease without obvious clinical consequences is increasingly referred to as cognitive or neural reserve.1, 5 Identification of factors associated with neural reserve has important implications for disease prevention. For example, one such factor is education. Clinicopathological studies suggest that the relation between quantitative measures of Alzheimer's disease pathology and level of cognition differ by duration of formal education.6 Another potential factor that could modify this relation is social networks. Social networks have been related to a reduced risk of death and a reduction in a wide variety of adverse health outcomes in old people.7 Several studies have also examined the relation between the extent of social ties and cognitive function and dementia. Most,8, 9, 10 but not all,11 showed that people with more extensive social networks were at reduced risk of cognitive impairment. Little is known about the cellular, molecular, and neuropathology of social networks and potential neurobiological mechanisms underlying this association. Although social networks could be directly related to the accumulation of Alzheimer's disease pathology, it seems more likely that social network size is related to reserve capacity capable of reducing the likelihood that the disease pathology will be clinically expressed as cognitive impairment. We aimed to test this hypothesis using data from the Rush Memory and Aging Project—a large, longitudinal, epidemiological, clinicopathological study of ageing and Alzheimer's disease.
Section snippets
Participants and procedures
Participants were elderly people without known dementia in the Rush Memory and Aging Project12 (see acknowledgments). Each participant gave written informed consent and an anatomical gift act for brain donation. The study was approved by the Institutional Review Board of Rush University Medical Center. More than 1100 people have agreed to participate and have completed their baseline clinical assessment. The overall annual follow-up rate of survivors exceeds 90%, and the autopsy rate exceeds
Results
Participants were about 81 years of age, had about 14 years of education, and were predominantly white, non-Hispanic (table 1). Mean MMSE was nearly 26 at baseline. Global cognitive function and other cognitive scores at baseline ranged from close to the mean for the entire cohort at baseline for working memory to nearly half a standard unit below the mean for episodic memory. At the last assessment before death, age was just over 87 years, mean MMSE score was 24, and cognitive scores ranged
Discussion
We found that the extent of social networks modified the relation between some measures of Alzheimer's disease pathology and level of cognitive function assessed proximate to death. The effect was evident with several measures of pathology acquired with different methodologies, but was strongest for neurofibrillary tangles. The effect persisted after controlling for various potentially confounding variables. It was evident across multiple domains of cognition, but was most evident for semantic
References (35)
- et al.
Influence of social network on occurrence of dementia: a community-based longitudinal study
Lancet
(2000) - et al.
An active and socially integrated lifestyle in late life might protect against dementia
Lancet Neurol
(2004) The neurobiology of social cognition
Curr Opin Neurobiol
(2001)- et al.
From social integration to health: Durkheim in the new millennium
Soc Sci Med
(2000) - et al.
Clinical, pathological, and neurochemical changes in dementia: a subgroup with preserved mental status and numerous neocortical plaques
Ann Neurol
(1988) - et al.
Pathological markers associated with normal aging and dementia in the elderly
Ann Neurol
(1993) - et al.
Alzheimer's neurofibrillary pathology and the spectrum of cognitive function: findings from the Nun Study
Ann Neurol
(2002) - et al.
Neuropathology of cognitively normal elderly
J Neuropathol Exp Neurol
(2003) - et al.
Cognitive reserve: implications for diagnosis and prevention of Alzheimer's disease
Curr Neurol Neurosci Rep
(2004) - et al.
Education modifies the relation of AD pathology to cognitive function in older persons
Neurology
(2003)
Social networks, host resistance, and mortality: a nine-year follow-up study of Alameda County residents
Am J Epidemiol
Social disengagement and incident cognitive decline in community-dwelling elderly persons
Ann Intern Med
Social resources and cognitive decline in a population of older African Americans and whites
Neurology
Social relationships, social support, and patterns of cognitive aging in healthy, high-functioning older adults: MacArthur studies of successful aging
Health Psychol
The Rush Memory and Aging Project: study design and baseline characteristics of the study cohort
Neuroepidemiology
Clinical diagnosis of Alzheimer's disease. Report of the NINCDS-ADRDA Work Group under the auspices of Department of Health and Human Services Task Force on Alzheimer's Disease
Neurology
Early and late life cognitive activity and cognitive systems in old age
JINS
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