The topic of healthy aging becomes increasingly important as the elderly segment of the American population ages. In 2000, there were an estimated 35 million people age 65 or older in the United States, accounting for almost 13% of the population [1
]. In 2011, the “baby-boom” generation will begin to turn 65, and by 2030, it is projected that one in five people will be aged 65 or older. The oldest-old population, 85 years and older, is currently the fastest growing segment of the older population.
With the increasing population of older adults, there is a growing interest in optimizing quality of life in old age and in early detection of cognitive decline with aging. Although it is well documented that aging is accompanied by a decline in several domains of cognition, studies have also shown that such decline is not common to all older people, and some older adults can in fact enjoy old age with good memory, concentration, executive function and other cognitive functions. Numerous studies report a link between AD-related pathology and cognitive decline [2
]; nonetheless, healthy cognition can also occur amidst a spectrum of brain pathology, where some individuals have brains relatively free of pathological lesions, while others show significant accumulations of pathology, despite intact cognition. In community based studies of cognition with autopsy [5
], it has been found that a third of people without dementia can have plaques and tangles that meet criteria for intermediate or even high likelihood of Alzheimer’s Disease (AD), as well as infarctions and Lewy bodies [8
]. As such, the correlation between neuropathological lesions and cognition is modest and accounts for about a quarter of the variance of cognition among older adults [9
The need and potential impact of research to identify factors that promote resistance to age-associated neurodegeneration is great. The concept of cognitive reserve has emerged to explain individuals’ ability to tolerate disease-related pathology in the brain without developing clinical symptoms or signs [13
]. A number of factors are thought to contribute to this reserve including education, occupational experience, and leisure activities. For example, individuals with high levels of educational attainment perform better on tests of cognitive function and exhibit less decline over time compared to those with lower education levels [14
]. Individuals in occupations involving higher mental demands also show better cognitive performance compared to those engaged in lower mental occupational demands [16
]. In addition, individuals who participate in cognitive activities such as reading and playing crosswords, and are engaged in their environment exhibit the least decline in cognitive function compared to those with disengaged lifestyle [17
]. Participation in leisure activities is also associated with a reduced risk of dementia [19
]. These findings, then, support the cognitive reserve hypothesis and suggest that such factors could be used as indicator of cognitive reserve.
The Rush Alzheimer’s Disease Center has two large, community-based, cohort studies of aging and AD that include organ donation: The Religious Orders Study (ROS) and the Rush Memory and Aging Project (MAP). The ROS and MAP studies have resulted in more than 200 peer-reviewed publications on a wide variety of issues related to healthy aging, AD and common chronic diseases of aging. These studies have examined a variety of environmental and psychosocial factors contributing to resilience, including socioeconomic status, psychosocial distress, and lifestyle activities in cognitive, physical and social spheres. Below, we will first briefly describe the two cohorts and report findings from these studies as they pertain to neuropathology and cognitive functioning in aging.