Aging and Cognition in Women
Chris Perkins
Worldwide, more than 470 million women are over 50 years of age and one-third of these will live into their 80s. It is anticipated that nearly two-thirds of the current US population will survive to 85 years or beyond.
Women have a longer life expectancy than men; thus in absolute numbers more women than men suffer from the neurodegenerative disorders that occur in very old age. Dementia is the most prevalent of these disorders, occurring in about 5% of people over 65 years of age and about 20% of those over 80. In 1997, of the 2.32 million people who were affected with Alzheimer’s type dementia in the United States, 68% were women (1). Once they develop Alzheimer’s disease, women on average live longer than men (2). Dementia is very much a women’s health problem.
Dementia is now the third most common neuropsychiatric disorder in high-income countries (3). However, as the population in developing countries ages, dementia is also becoming commoner there. In China, for example, at least 10% of the population are now over 60 years of age. Although that rate of dementia is low compared to the rate for persons of Caucasian ancestry, an estimated 5 million people in China, mostly women, have
dementia. Social trends in Asia, such as smaller families and increased opportunity for paid work for women, mean that the family is less able to fulfill the traditional role of caring for aging parents. Currently in China about 1 in 10 older persons live alone (4). In India, women surviving into old age are often vulnerable and disadvantaged and may be the only caregivers for the disabled (5). In Latin America and the Caribbean, where populations are aging rapidly, most of the elderly are women living in urban centers. A lifetime of ill health and poverty makes them vulnerable to the diseases of old age (6).
dementia. Social trends in Asia, such as smaller families and increased opportunity for paid work for women, mean that the family is less able to fulfill the traditional role of caring for aging parents. Currently in China about 1 in 10 older persons live alone (4). In India, women surviving into old age are often vulnerable and disadvantaged and may be the only caregivers for the disabled (5). In Latin America and the Caribbean, where populations are aging rapidly, most of the elderly are women living in urban centers. A lifetime of ill health and poverty makes them vulnerable to the diseases of old age (6).
Women not only make up a high proportion of the people suffering from dementia, but they are also the main caregivers, both as family members and as employees in the aged care sector. Their services are often underrecognized and undervalued. As the “baby boomers” enter old age and life expectancy in developing countries increases, governments and insurers are starting to realize that the support of large numbers of older people with dementing illnesses will become prohibitively expensive. Thus preventive, diagnostic, and treatment strategies for the dementias are now receiving urgent attention. In this chapter we consider the changes in cognition that may occur with age and the diagnosis, prevention, and management of dementia. We discuss caregiving for older people with cognitive impairment and the risks of exploitation and abuse in this very vulnerable population.
“NORMAL” COGNITIVE CHANGES WITH AGE
Older people often report difficulties with cognitive ability, especially memory. It is difficult to determine what changes in cognition can be anticipated with normal aging. People become increasingly different from each other as they age, resulting in increased variability on tests of cognition. Thus, average scores across an age group may be less relevant than for younger people. Unrecognized illness (including dementia) or medication can also affect cognitive ability and confound the results of testing.
Comparing young and old in cross-sectional studies fails to account for generational differences in diet, health care, education, and other experiences between cohorts. These studies may exaggerate the age-related deterioration in cognition. In longitudinal studies that repeatedly test a group over many years, the less healthy subjects tend to drop out, leaving more of the more cognitively able members of the cohort. Such studies minimize the differences in cognition between older and younger people. However, some changes in cognitive function with age are broadly accepted.
LEARNING AND MEMORY
Declarative (or episodic) memory declines over time in longitudinal studies. Declarative memory is the recognition or recall of previously presented information; an example is the free recall of word lists or narrative material. Younger people may have better strategies for remembering over the short term; for example, when memorizing a list of objects they will group them somehow, such as by the first letter of the name. If older people are taught to do this, their recall improves significantly.
Older adults may have more difficulty with working memory, that is, more difficulty simultaneously retaining and processing information. Remote recall for many years past is usually good.
SPEED OF PROCESSING
Perceptual speed is the speed with which simple perceptual comparisons can be performed, as measured, for example, by timed tasks requiring symbol substitution. When age-related differences in perceptual speed are controlled for in some standard psychological tests, some other age-related differences disappear.
The commonly used Weschler Adult Intelligence Scale-Revised (7) has verbal and performance tasks. For older persons taking the test, little change is found on the verbal tasks that reflect a person’s accumulated experience, education, and knowledge (crystallized intelligence). The performance tasks, however, begin to decline in midlife. These depend on speed and mental flexibility, which diminish over time. How much these changes actually affect an older person’s functioning is unclear.
ATTENTION
The ability to sustain attention does not appear to change with age although it becomes more difficult to ignore extraneous stimuli and perhaps to shift or divide attention.
LANGUAGE
Apart from the well-known difficulty of retrieving names or other words, language does not normally deteriorate (8).
COGNITIVE IMPAIRMENT NO DEMENTIA (CIND)
The boundary between normal aging and pathologic change that would predict likely progression to dementia has yet to be identified. Since the development of the antidementia drugs, it has become important to try to clarify this boundary. If early cognitive impairment can be detected in an elderly person (and has not already resulted in sufficient functional or intellectual decline to merit a diagnosis of dementia), then appropriate treatment may delay or prevent the onset of the dementia.
The focus of investigation in this area has mainly been on age-associated memory impairment (AAMI), also known as amnestic mild cognitive impairment (aMCI). This focus has helped detect decline in people who may go on to develop Alzheimer’s disease, memory impairment being an important early symptom. Amnestic MCI is defined as performance at 1.5 SD below age norms on a memory test, subjective memory complaints, intact general cognition, and not meeting criteria for dementia (9). However, non-Alzheimer forms of dementia often show deterioration in other areas of cognitive performance before memory declines. “Cognitive impairment no dementia,” or CIND, includes other cognitive deficits as well as memory and may predict other forms of dementia as well as Alzheimer’s disease. CIND, not consistently defined as yet, is characterized by difficulty with memory and/or other areas of cognition not sufficiently severe to meet criteria for dementia (10). Various studies show high rates of CIND in the elderly population (10.7% to 23.4% in those over 65), with the rate increasing with the age of the population studied (11,12). Of possible risk factors for CIND, only education has
been shown to predict its rate in population studies; people with fewer years of formal education show a greater rate of cognitive decline than more educated persons (12,13). The current cohort of elderly women may show more cognitive deterioration than their better educated male peers. A recent community study of a sample of people 70 to 79 years old showed an insignificant decrease in the number of cognitively normal women compared with the number of cognitively normal men (14).
been shown to predict its rate in population studies; people with fewer years of formal education show a greater rate of cognitive decline than more educated persons (12,13). The current cohort of elderly women may show more cognitive deterioration than their better educated male peers. A recent community study of a sample of people 70 to 79 years old showed an insignificant decrease in the number of cognitively normal women compared with the number of cognitively normal men (14).
DEMENTIA
Dementia is defined as the development of multiple cognitive deficits (including memory impairment) due to
The direct physiological effects of a general medical condition
The persisting effects of a substance, or
Multiple etiologies (DSM-IV)
These cognitive deficits are often accompanied by psychological symptoms such as anxiety, delusions, and hallucinations. Personality and behavioral changes occur, and there may be motor disturbances, depending on the type of dementia.
Of the many different types of dementia, the most common are Alzheimer’s disease (50%-60% of cases); vascular dementia (15%-20%); mixed Alzheimer’s and vascular dementia (10%); and Lewy body dementia (15%). The frontotemporal dementias (about 10%) and subcortical dementias form a heterogeneous group of diseases, often affecting people with movement disorders. The boundaries between the different types of dementia are blurred clinically and neuropathologically. Recent research has shown that vascular risk factors increase the likelihood of Alzheimer’s dementia as well as vascular dementia (19,20). Brain infarction, detected on MRI, appears to hasten or precipitate the clinical expression of Alzheimer’s disease (21). This suggests that the dementias are not necessarily separate clinical entities.
In some studies the incidence of Alzheimer’s disease is higher in women than men. (22). Others (23) find only borderline differences or an increase in the female over male rate after 90 years of age only. However, men have a higher rate of vascular dementia (24), and there is a slight excess of males with Lewy body dementia (25).
The male:female ratio in the frontotemporal and subcortical dementias depends on the etiology. However, given women’s longevity and the increased prevalence of dementia in people aged over 80, in absolute numbers many more women than men suffer from dementia.
PREVENTING DEMENTIA
Possible preventive approaches are described in the following paragraphs.
Education and cultural activities.
As with CIND, the incidence of dementia is lower in people with more years of education. A study controlled for education found that participation in intellectual and cultural activities after formal education reduced the risk of dementia for women but not for men (27).
Medications.
Weight.
Women who are overweight in old age may be more prone to developing dementia. For every unit of increase in the body mass index score, the risk of developing Alzheimer’s disease increased by 36%. These increases were not found in men (27).
Richness of expression in youth.
In the Nun study (a longitudinal study of the Sisters of Notre Dame in the United States), those with a wide and expressive writing style in youth were less prone to develop dementia. Low linguistic ability early in life may reflect suboptimal neurologic and cognitive development, which could increase susceptibility to the development of Alzheimer’s disease pathology in later life (28).
Antioxidants.
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