Fluid and Crystallized Intelligence

Fluid intelligence (often called native intelligence) consists of skills that are biologically determined, independent of experience or learning. It is associated with flexibility in thinking, inductive reasoning, abstract thinking, and integration. Fluid intelligence “enables people to identify and draw conclusions about complex relationships” (Miller, 2008, p. 187). Crystallized intelligence is composed of knowledge and abilities that the person acquires through education and life. Measures of crystallized intelligence include verbal meaning, word association, social judgment, and number skills. Older people perform more poorly on performance scales (fluid intelligence), but scores on verbal scales (crystallized intelligence) remain stable. This is known as the classic aging pattern (Hooyman and Kiyak, 2011). The tendency to do poorly on performance tasks may be related to age-related changes in sensory and perceptual abilities as well as psychomotor skills. Speed of cognitive processing and slower reaction time also affect performance.

Late adulthood is no longer seen as a period when growth has ceased and cognitive development halted; rather it is seen as a life stage programmed for plasticity and the development of unique capacities. Older people do maintain their ability to understand situations and learn from new experiences. These findings are significant to satisfaction in late life, because the capacity for effective lifestyle management and one’s cognitive resources contribute to adaptation and enjoyment. Chapter 6 discusses learning in later life and presents effective teaching-learning strategies.

Memory

Memory is defined as the ability to retain or store information and retrieve it when needed. Memory is a complex set of processes and storage systems. Three components characterize memory: immediate recall; short-term memory (which may range from minutes to days); and remote or long-term memory. Biological, functional, environmental, and psychosocial influences affect memory development throughout adulthood. Recall of newly encountered information seems to decrease with age, and memory declines are noted in connection with complex tasks and strategies. Even though some older adults show decrements in the ability to process information, reaction time, perception, and capacity for attentional tasks, the majority of functioning remains intact and sufficient.

Familiarity, previous learning, and life experience compensate for the minor loss of efficiency in the basic neurological processes. In unfamiliar, stressful, or demanding situations, however, these changes may be more marked. Normal older adults may complain of memory problems, but their symptoms do not meet the criteria for mild cognitive impairment (MCI) or dementia. The term age-associated memory impairment (AAMI) has been used to describe memory loss that is considered normal in light of a person’s age and educational level. This may include a general slowness in processing, storing, and recalling new information, and difficulty remembering names and words. However, these concerns can cause great anxiety in older adults who may fear dementia. Many medical or psychiatric difficulties (depression, anxiety) also influence memory abilities, and it is important for older adults with memory complaints to have a comprehensive evaluation.

Cognitive stimulation and memory training may be helpful for cognitively intact older adults, as well as for those with cognitive impairment (Camp and Skrajner, 2004; Yevchak et al., 2008). Cognitive stimulation and memory training techniques include mnemonics (strategies to enhance coding, storage, and recall), internal and external aids, reasoning and speed-of-processing training, cognitive games (e.g., Scrabble, chess, crossword puzzles), and spaced retrieval techniques. Many games and aids are available that may be useful to enhance memory and stimulate cognitive function. Continued attention to diet, exercise, cardiovascular risk factors, and meaningful activities are also important to brain health (Chapter 2 and Table 19-3).

Cognitive Impairment

Cognitive impairment (CI) is a term that describes a range of disturbances in cognitive functioning, including disturbances in memory, orientation, attention, and concentration. Other disturbances of cognition may affect intelligence, judgment, learning ability, perception, problem solving, psychomotor ability, reaction time, and social intactness.

Cognitive Assessment

An older person with a change in cognitive function needs a thorough assessment to identify the presence of specific pathological conditions. Pathological conditions causing impairment of cognition include delirium, dementia, and depression. The literature reveals that both physicians and nurses in all settings routinely fail to appropriately assess an individual’s cognitive functioning. Pathological conditions are often undiagnosed, reversible causes not identified, and opportunities for early intervention missed. As a result, the person experiences greater impairment and functional decline (Braes et al., 2008).

Some of the reasons for this include the complexity of cognitive assessment and the existence of several conditions with similar symptoms (dementia, depression, delirium) (Table 19-1). Other reasons include the often atypical symptom presentation in older adults and the belief, on the part of health care professionals as well as older people, that alterations in cognitive functioning are part of the “normal” aspects of aging (Braes et al., 2008; Evans, 2007; Fletcher, 2008). Older people may be diagnosed with dementia as a result of an occurrence of confusion or altered mental status without a comprehensive evaluation. Older adults should be routinely and regularly assessed for cognitive function in all settings, and nurses must have the skills to recognize cognitive impairment and monitor cognitive functioning. “Assessment of cognitive function is the first and most critical step in a cascade of strategies to prevent, reverse, halt, or minimize cognitive decline” (Braes et al., 2008, p. 42). (Chapter 7 discusses assessment tools used to evaluate cognitive function).

Etiology

The development of delirium is a result of complex interactions among multiple causes. Delirium results from the interaction of predisposing factors (e.g., vulnerability on the part of the individual due to predisposing conditions, such as cognitive impairment, severe illness, and sensory impairment) and precipitating factors/insults (e.g., medications, procedures, restraints, iatrogenic events). While a single factor, such as an infection, can trigger an episode of delirium, several co-existing factors are also likely to be present. A highly vulnerable older individual requires a lesser amount of precipitating factors to develop delirium (Inouye et al., 1999; Voyer et al., 2010).

The exact pathophysiological mechanisms involved in the development and progression of delirium remain uncertain, and further research is needed to understand its neuropathogenesis. Delirium is thought to be related to disturbances in the neurotransmitters in the brain that modulate the control of cognitive function, behavior, and mood. Irving and Foreman (2006) note that “there is growing evidence of cholinergic failure as a common pathway in delirium” (p. 122). The causes of delirium are potentially reversible; therefore accurate assessment and diagnosis are critical. Delirium is given many labels: acute confusional state, acute brain syndrome, confusion, reversible dementia, metabolic encephalopathy, and toxic psychosis.

Incidence and Prevalence

Delirium is a prevalent and serious disorder that occurs in elders across the continuum of care. Estimates are that delirium may affect up to 42% of hospitalized older adults and as many as 87% of older adults in intensive care units (ICUs) (Cole and McCusker, 2009; Marcantonio et al., 2010; Sweeny et al., 2008). Older people who have undergone surgery and those with dementia are particularly vulnerable to delirium. The prevalence of delirium is as high as 65% after orthopedic surgery, particularly hip fracture repair (Rigney, 2006). Among older people experiencing cardiac surgery, as many as 20% to 25% experience delirium, affecting even those without any documented preoperative cognitive impairments (Clarke et al., 2010). A 16% delirium rate in patients newly admitted to subacute care has been reported. More than 50% of these patients are still delirious one month after admission (Marcantonio et al., 2010). Delirium is associated with increased morbidity, mortality, and institutionalization, independent of age, co-existing illnesses, or illness severity (Witlox et al., 2010).

The incidence of delirium superimposed on dementia (DSD) ranges from 22% to 89% (Tullmann et al., 2008). Older patients with dementia are three to five times more likely to develop delirium, and it is less likely to be recognized and treated than is delirium without dementia. DSD is associated with high mortality among hospitalized older people (Bellelli et al., 2008). Changes in the mental status of older people with dementia are often attributed to underlying dementia, or “sundowning,” and not investigated. This is particularly significant since about 25% of all older hospitalized patients may have Alzheimer’s disease or another dementia (Voelker, 2008). Delirium can accelerate the trajectory of cognitive decline in individuals with Alzheimer’s disease. Further research is needed to determine whether prevention of delirium may delay cognitive decline in individuals with Alzheimer’s disease (Fong et al., 2009). Despite its prevalence, DSD has not been well investigated, and there are only a few relevant studies in either the hospital or community setting.

Recognition of Delirium

Delirium is a medical emergency and one of the most significant geriatric syndromes (Waszynski and Petrovic, 2008). However, it is often not recognized by physicians or nurses. Studies indicate that delirium is unrecognized in 66% to 84% of patients (Pisani et al., 2006; Balas et al., 2007). A comprehensive review of the literature suggested that “nurses are missing key symptoms of delirium and appear to be doing superficial mental status assessments” (Steis and Fick, 2008, p. 47). Factors contributing to the lack of recognition of delirium among health care professionals include inadequate education about delirium, a lack of formal assessment methods, a view that delirium is not as essential to the patient’s well-being in light of more serious medical problems, and ageist attitudes (Kuehn, 2010a; Waszynski and Petrovic, 2008). Failure to recognize delirium, identify the underlying causes, and implement timely interventions contributes to the negative sequelae associated with the condition (Tullmann et al., 2008; Kuehn, 2010a).

Dahlke and Phinney (2008) investigated interventions nurses use to assess, prevent, and treat delirium, as well as the challenges and barriers nurses face in caring for patients with delirium in the acute care setting. The authors concluded that cognitive changes in older people are often labeled confusion by nurses and physicians, are frequently accepted as part of normal aging, and are rarely questioned. If the nurse believed that confusion was normal in older adults, he or she would be less likely to recognize symptoms of delirium as a medical emergency necessitating their attention and intervention. Confusion in a child or younger adult would be recognized as a medical emergency, but confusion in older adults may be accepted as a natural occurrence, “part of the older person’s personality” (p. 46).

In the Dahlke and Phinney study, nurses reported that caring for patients with delirium was seen as “annoying, frustrating and not interesting” (2008, p. 45). Nurses expressed that the care of older patients with delirium interfered with what was perceived as the “real work” of caring for a medical or surgical patient. Insufficient knowledge and inadequate time and resources also influenced appropriate care. The authors conclude that nurses are faced with the predicament of fitting care for older adults into a system that does not recognize the unique needs of this population. Clearly, education and attitudes about older people must be addressed if we want to improve care outcomes for the growing number of older adults who will need care.

Risk Factors for Delirium

The risk of delirium increases with the number of risk factors present. The more vulnerable the individual, the greater the risk. The multifactorial model for delirium (MMD), developed by Inouye and Charpentier (1996), can be used to guide identification of risk factors in hospitalized older adults. In the first study examining the use of this model in long-term care, Voyer and colleagues (2010) report that the MMD is relevant among this population and can be used to prevent delirium and improve care outcomes in this setting.

Identification of high-risk patients, risk factors, prompt and appropriate assessment, and continued surveillance are the cornerstones of delirium prevention. More than 35 potential risk factors have been identified for delirium. Among the most predictive are immobility, functional deficits, use of restraints or catheters, medications, acute illness, infections, alcohol or drug abuse, sensory impairments, malnutrition, dehydration, respiratory insufficiency, surgery, and cognitive impairment. Unrelieved or inadequately treated pain significantly increases the risk of delirium (Irving and Foreman, 2006). Medications account for 22% to 39% of all delirium, and all medications, particularly those with anticholinergic effects and any new medications, should be considered suspect. Invasive equipment, such as nasogastric tubes, intravenous (IV) lines, catheters, and restraints, also contribute to delirium by interfering with normal feedback mechanisms of the body (Box 19-3).

Clinical Subtypes of Delirium

Delirium is categorized according to the level of alertness and psychomotor activity. The clinical subtypes are hyperactive, hypoactive, and mixed. Box 19-4 presents the characteristics of each of these clinical subtypes. In non-ICU settings, approximately 30% of delirium is hyperactive, 24% hypoactive, and 46% is mixed. Because of the increased severity of illness and the use of psychoactive medications, hypoactive delirium may be more prevalent in the ICU. Although the negative consequences of hyperactive delirium are serious, the hypoactive subtype may be missed more often and is associated with a worse prognosis because of the development of complications such as aspiration, pulmonary embolism, pressure ulcers, and pneumonia. Increased hospital stays, longer duration of delirium, and higher mortality have been associated with hypoactive delirium.

Consequences of Delirium

Delirium has serious consequences and is a “high priority nursing challenge for all nurses who care for older adults” (Tullmann et al., 2008, p. 113). Delirium results in significant distress for the patient, his or her family and significant others, and nurses. Delirium is associated with increased length of hospital stay and hospital readmissions, increased services after discharge, and increased morbidity, mortality, and institutionalization, independent of age, co-existing illnesses, or illness severity (Witlox et al., 2010).

Recent research indicates that delirium is associated with lasting cognitive impairment and psychiatric problems. While the majority of hospital inpatients recover fully from delirium, a substantial minority will never recover or recover only partially. Patients with delirium that remains unresolved at discharge should be screened again at three months and followed closely. The persistence of delirium after discharge may interfere with the ability to manage chronic conditions and contribute to poor outcomes (Cole and McCusker, 2009). Screening all older adults before they leave the hospital may help to identify those in need of specific transitional care (Chapter 16) with more frequent follow up after hospitalization (Lindquest et al., 2011). Further research is needed to determine the reasons for the long-term poor outcomes, whether characteristics of the delirium itself (subtype or duration) influence prognosis, and how the long-term effects might be decreased.