Chapter 59 Geriatric Rehabilitation
Geriatric rehabilitation addresses problems that affect not only the individual patient, but also society at large. There are major economic ramifications when individuals can no longer care for themselves. Increased longevity, with an increase in the absolute numbers of elderly, has increased the impact on society. Life expectancy has increased in a number of countries. The average life expectancy at the age of 65 years in the United States is currently 17 years.108
Frailty
Frailty can be defined as age- and disease-related loss of adaptation, such that events of previously minor stress result in disproportionate biomedical and social consequences.107 Frailty is difficult to quantify, but it is the generalized decline in multiple systems with the loss of functional reserve.42 In an attempt to more precisely measure frailty, one can measure mobility, balance, muscle strength, motor processing, cognition, nutrition, endurance, and physical activity.42 In one definition, Fried et al.49 defined frailty as a clinical syndrome in which three or more of the following were present: (1) unintentional weight loss of at least 10 lb over the past year; (2) self-reported exhaustion; (3) weakness (grip strength); (4) slow walking speed; and (5) low physical activity. This was based on data from 5317 men and women 65 years and older. Frailty was held by the authors to be distinct from both disability and from comorbidity, although frailty can be a cause of disability. The authors postulated that one pathway in the development of frailty could be attributable to the physiologic changes of aging, with a separate pathway attributable to diseases and comorbidities.
A potential pitfall of these measurements is that people perceive functional difficulties at differing thresholds, which are influenced by social environment and economic status. Perceived abilities can also be different than actual performance. Quality-of-life instruments developed on younger patients might have poor reliability and validity in elderly people with multiple health problems.42 The body maintains itself in homeostasis. What would be a minor perturbation in a younger individual might trigger a much larger set of problems in an older person. For example, a urinary tract infection in an older person can lead to confusion, with a subsequent fall and hip fracture. Frailty, despite the difficulties in quantification, is a concept that clinicians recognize.
Changes in the Body With Aging
Muscle Changes
Older adults lose both strength and the ability to produce force rapidly.11 Sarcopenia is the loss of muscle mass and strength with aging.67,114 There is a loss of the number of myocytes and a reduction of the protein content of the remaining muscle cells. Muscle strength decreases with aging at the level of single muscle fibers and force per unit area. Protein synthesis decreases, especially myosin heavy chains, with a disproportionate atrophy of type 2a (fast-twitch) fibers.98 A decreased myosin concentration can play a key role, with a slower shortening velocity of single muscle fibers.36 Aging muscle has a disproportionate loss of fast muscle fibers, with an increased proportion of muscle fibers with multiple myosin isoforms. Thus there is a blurring between type 1 and type 2 fibers, with the muscle overall having more slow-twitch characteristics than in young adults.11 Muscle power decreases by 3.5% per year, whereas strength decreases by 1.4% to 2.5% per year beyond the age of 60 years.11
Sarcopenia is probably driven by a combination of catabolic action and a reduction in anabolic influences.114 There is an increase in catabolic cytokines, such as tumor necrosis factor-α, interleukin (IL)-6, IL receptor antagonist, and IL-1β. Anabolic stimuli decrease, including estrogen, testosterone, growth hormone, protein intake, physical activity, and central nervous system input to promote movement.114 In both the healthy and the frail elderly, it is the type 2 fast-twitch fibers that are lost.124 α-Motor neuron dropout occurs with a reduced number of them in the elderly. Sarcopenia does not typically cause a decrease in body weight, because the percentage of fat increases.23
The role of cytokines in mediating muscle mass and strength is just beginning to be understood. For example, in a cross-sectional analysis of 617 women aged 70 to 79 years, a decline in insulin-like growth factor-1 was associated with poor knee extensor strength, slow walking speed, and self-reported disability.26 In a cross-sectional study of 3075 adults aged 70 to 79, the inflammatory markers C-reactive protein and IL-6 were lower in those who had higher levels of exercise and in those who used antioxidant supplements regardless of exercise status.30 Adipose tissue has its own metabolic activity, including the secretion of inflammatory factors.138 Increases in body fat might facilitate inflammation, with a differing role played by abdominal fat versus fat in the extremities.138
The decline in muscle strength is not the same in all muscle groups. In a study of 120 men and women aged 46 to 79 years who were observed over a 10-year period,67 women had slower rates of decline in elbow flexors and extensors (2% per decade) compared with men (12% per decade). In both men and women, knee extensor strength decreased by 14% per decade, and knee flexor strength by 16% per decade.
Mitochondrial function declines with old age.83 One theory is that a sedentary lifestyle leads to decreased spontaneous physical activity (as distinct from voluntary purposeful activity), which further decreases mitochondrial function. Data are not yet available to determine if endurance exercise can delay or prevent this decline.83
Older adults can have limitations in maximally activating muscle because of neural changes, such as increased agonist-antagonist coactivation, decreased motor neuron excitability at the spinal cord level caused by decreased afferent input, and inefficient transmission at the neuromuscular junction.11 With training, young adults show more adaptations in spinal cord relay components, whereas older adults might rely more on supraspinal influences.11 Older adults typically use a higher percentage of minimal knee strength than young adults, which can lead to more fatigue because they are working near full capacity.11 The elderly can also have reduced power, because of a lack of rapid force development.11
Gait Changes
From 8% to 19% of noninstitutionalized older adults have difficulty walking, and this increases to 67% of nursing home residents.3 Gait speed typically declines at the rate of 0.2% per year up to the age of 63 years, and then 1.6% after age 63 in older adults who are relatively free of neurologic, cognitive, or cardiovascular problems.3 Conditions associated with faster gait speed include greater hip extension, and ankle dorsiflexion and plantar flexion range of motion.3
Gait in the elderly is characterized by increased double-limb support, as well as by slower speed, shorter stride length, and a broader base of support. Pelvic rotation decreases and postural responses are slower. Gait studies have been done to identify factors associated with falling in the elderly (Boxes 59-1 and 59-2). In the subset of older people who fall, stride-to-stride variability in gait is increased.62,92 Maki92 found that reduced stride length, reduced speed, and increased double-support time are associated with a fear of falling. His study also showed that increased stride-to-stride variability in length, speed, and double support was associated with actual falling. Stride-to-stride variability was the best single predictor of falling. In another study of elderly women with a mean age of 75 years, the peak ankle dorsiflexion power had strong associations with stair climbing time and chair rise time. Plantar flexion isometric strength was strongly associated with habitual and maximal gait velocity.129 The study by Grabiner et al.58 also showed that when young and elderly “nonfallers” were studied, the older subjects had a significantly larger stride width variability.
Osteopenia and Osteoporosis
The elderly have an increased incidence of osteopenia and osteoporosis. Osteopenia is defined as bone mineral density more than one standard deviation below the young adult level (T <–1 but >–2.5). Osteoporosis is present if the T score is less than –2.5.106 This occurs in both genders, but is more common in women. Risk factors for osteopenia and osteoporosis include age, family history, glucocorticoid therapy, and smoking.106,126
Osteoarthritis
Degenerative joint disease becomes much more common in the aged. Arthritis affects more than 60% of women and 50% of men who are 70 years and older.13 The reported incidence and prevalence of osteoarthritis vary depending on whether one uses radiologic findings, clinical symptoms, or a combination to define cases.85 Limitations in range of motion can go unreported in some instances, because the person is unaware of the loss of range of motion as a result of its gradual progression.117
Osteoarthritis is the most prevalent articular disease in adults 65 years and older.85 Because there is a strong association with aging, attempts have been made to determine whether osteoarthritis is a distinct disease.85 In osteoarthritis, there are differences in the water content ratio of certain cartilage constituents, and an increase in degradative enzyme activity compared with that in nonosteoarthritic joints. It is possible that the reduction in chondrocyte density with aging leaves cartilage vulnerable to degeneration and osteoarthritis.85
Changes in Special Senses
Vision declines with age. The lens has less adaptation. Macular degeneration, cataracts, and glaucoma become more prevalent with age. Decreased auditory acuity frequently develops. The usual pattern is a loss of higher frequencies; people with this type of hearing loss can hear speech but have difficulty understanding it.47 With hearing loss progression, the lower frequencies are affected also, making it difficult to understand vowels and what is being said, especially in a loud setting.47
Cardiovascular Changes
With aging the cardiovascular system has decreased arterial compliance, increased systolic blood pressure, left ventricular hypertrophy, decreased baroreceptor sensitivity, and decreased sinoatrial node automaticity.108 The exercise-induced adaptations that occur in younger people, such as increased peripheral arteriovenous oxygen difference and increased cardiac size, stroke work, cardiac output, and left ventricular function,2 are not as available to the elderly. Older patients with coronary artery disease have age-related increases in left ventricular and arterial wall stiffness and thickening, which limit some adaptations with conditioning.2 In the operative setting, maintaining intravascular volume is important, because the aged heart depends on preload more than in the younger person. Because after-load is increased by outflow tract stiffness, there is decreased sensitivity to catecholamines and impaired vasoconstrictive responses in the elderly.113
Pulmonary Changes
Lung compliance increases and thoracic wall mobility decreases in the elderly, with a 20% increase in the effort needed to overcome elastic resistance.46 Vital capacity typically decreases 40% to 50% by the age of 70 years.46 The net effect is that during exertion, the elderly must rely on increased respiratory frequency rather than increased tidal volume.46
Genitourinary Changes
Renal blood flow decreases with age,22,29 as does glomerular filtration rate.108 A 50-kg woman with a serum creatinine level of 1.0 mg/dL has a calculated creatinine clearance of 62 mL/min if she is 35 years of age, but only 32 mL/min if she is aged 85 years old.29 Because serum creatinine reflects muscle mass, a normal serum creatinine level can be seen even with a reduced glomerular filtration rate.22 Urinary incontinence can develop on the basis of stress, or because of overflow secondary to prostatic hypertrophy. Increased collagen content causes decreased bladder distensibility.113 Decreased estrogen predisposes to incontinence by causing urethral sphincter changes.113 Subjective thirst decreases in the elderly, which can negatively affect fluid balance.113
Gastrointestinal Changes
There are many reasons for decreased food intake in the elderly.97 Odor and taste can be decreased. Cholecystokinin levels increase with aging, causing gastric emptying to slow and increasing the effect of antral stretch to signal satiation. There can be a decline in the central feeding drive. If disease causes cytokine release, these immunoregulatory peptides cause anorexia, muscle wasting, and decreased albumin synthesis.
Dysphagia can develop because of dental problems or achalasia. The time from pharyngeal entry of food to laryngeal elevation increases.41. Stomach acid decreases, with subsequent impaired absorption of vitamin B12, calcium, iron, zinc, and folic acid.112,125 Thirst sensation is impaired and gut motility decreases. Hepatic metabolism is altered, with corresponding changes in drug clearance. The potency and duration of action of some drugs are increased.22 Hepatic blood flow decreases 12% to 40% in the elderly, and liver size decreases, with a resulting reduction in first-pass metabolism of drugs.29 Impairment of normal liver function can also alter how a drug is treated in the liver, as drug interactions can alter liver enzymes and subsequent drug processing.22
Malnutrition affects the elderly differently than younger people. Elderly patients (mean age, 79 years) were compared with middle-aged (mean age, 48 years) in a group with chronic malnutrition. The middle-aged patients lost fat mass, fat-free mass, and body cell mass in equal proportions, but the elderly patients proportionately lost more fat-free mass and body cell mass. Therefore the elderly were losing proportionately more from muscle and other body organs.118
Endocrine Changes
Changes in the endocrine system can cause deterioration in glucose tolerance. Hormonal changes that typically occur include decreased estrogen, testosterone, and growth hormone. Temperature regulation is impaired.113 End-organ responsiveness to medications can be different in the elderly, but this is just beginning to be explored.53 There is an age-related decline in immune function, which in some studies has been improved with vitamin supplements.112 Vitamin D deficiencies can exist because of inadequate intake, decreased exposure to the sun, and impaired efficiency in the conversion of the inactive to active forms.66
Diseases That Are More Common in the Elderly
Parkinson Disease
Parkinson disease is present in 1% of people older than 65 years,7 and clinically manifests with tremor, rigidity, and bradykinesia. Twenty percent of patients with Parkinson disease also develop dementia.16 The tremor is present at rest and increases with stress.7 Voluntary movement is slow. Gait is characterized by small shuffling steps without arm swing. It is difficult for the patient to initiate walking or other position changes.7 The gait can be festinating, in which gait speed increases as the patient attempts to prevent falling forward because of an abnormal center of gravity. Turning is particularly difficult and unsteady.7
Dementia
Dementia is found in 1.5% of people aged 65 to 70 years, and increases to 25% of people 85 years and older.114 The most common causes of dementia in the elderly are Alzheimer disease, vascular (multiinfarct) dementia, diffuse white matter changes (also called Binswanger dementia), alcoholism, Parkinson disease, and drug or medication intoxication.16
Depression must always be differentiated from dementia in the elderly.128 Dementia should also be differentiated from benign forgetfulness of the elderly. The workup for dementia typically includes obtaining a serum vitamin B12 level, thyroid function tests, serum electrolyte levels, a complete blood cell count, serology for syphilis, and brain imaging. Depending on the clinical setting, urine toxicology screen, lumbar puncture, and a general medical workup can be needed. If there is a history of falls or the patient is receiving anticoagulants, subdural hematoma should be ruled out. Infections should be ruled out. Acquired immunodeficiency syndrome can produce dementia in the elderly. The adverse effects of medications can sometimes include dementia, and depression can masquerade as dementia.
Dementia must be differentiated from acute confusion. Delirium is an acute confusional state with a fluctuating time course, with impaired cognition, attention, and level of consciousness.69 Neurologists prefer the term acute confusional state.111 Inattention and disorientation are the primary early signs, with a defect in attention. There can be drowsiness as well. The patient has decreased mental clarity, coherence, comprehension, and reasoning.111 It can be clinically challenging to determine what is chronic and what is new when an elderly patient has confusion in the postoperative setting, because baseline dementia is the major risk factor for delirium (Box 59-3).113 Risk factors include age, preoperative cognitive impairment, poor functional status, alcohol use, and polypharmacy.113 In the postoperative period, undertreated pain can lead to delirium.113 Intraoperative blood loss and a postoperative hematocrit less than 30% are associated with an increased risk for postoperative delirium.113
Mild cognitive impairment is shown clinically by memory loss greater than expected for age, but this is not Alzheimer disease.105 There are mild deficits in memory or some other aspect of cognition, with a progression to Alzheimer disease at a higher rate than healthy controls.105 Cognitive dysfunction can show up first in executive functioning. In a study of community dwelling women aged 70 to 79 years at baseline, observed for 9 years, a decline in executive function preceded memory loss by about 3 years.27 Executive function is needed for planning, initiating, prioritizing, and carrying out a series of goal-directed actions.27
Approximately 10% of people older than 70 years have significant memory loss, and in more than half of the cases this is attributed to Alzheimer disease.15 The prevalence is 1% among those aged 60 to 64 years, and 40% among those 85 and older.34 Alzheimer dementia typically progresses slowly over several years. Confrontation naming of items to command is typically impaired early in the course.15 Patients have difficulty learning and recalling new information, and there is a progressive language disorder.34 Visuospatial skills are disturbed.34 Executive function skills are impaired, including planning, judgment, and insight.34 Apraxia with sequential motor tasks can occur.15 Alzheimer dementia can also feature delusions and hallucinations.15 Social inhibitions are lost, and the sleep-wake cycle is disturbed.15 A shuffling gait with rigidity can develop.15 The disease typically has an 8- to 10-year duration. The pathologic features typically include plaques with amyloid and neurofibrillary tangles in the neuronal cytoplasm.
Normal Pressure Hydrocephalus
The hallmark signs of normal pressure hydrocephalus are dementia, gait disturbance, and urinary incontinence.16 Normal pressure hydrocephalus can be idiopathic or related to prior meningitis or subarachnoid hemorrhage.16 The reduced physical turgor of the brain tissue with aging is thought by some experts to allow even normal pressure to produce hydrocephalus and brain atrophy. In some cases the patient’s condition can be dramatically reversed by shunting to achieve a reduction in central nervous system fluid pressure.
Cancer
The incidence and prevalence of most malignancies increase with age up to at least 85 years of age.10 The increasing incidence could be because of the length of time for a carcinogenic factor to take effect, as well as molecular changes occurring with aging that can favor certain cancers.10 Tumors can behave differently in older patients than in those who are younger, and this has to be kept in mind when designing a treatment plan.10
Osteoarthritis
Osteoarthritis is the major disease that limits activity in the elderly.110 Risk factors are increased age, obesity, quadriceps weakness, impaired proprioception, heavy physical activity, lack of estrogen replacement in women, and knee injuries.110
Traumatic Brain Injury and Spinal Cord Injury
Older patients sustain more traumatic brain injury and spinal cord injury in domestic falls than do younger patients.110 Patients older than 50 years typically require longer lengths of hospitalization for these injuries, with the cost being twice as high as for younger patients.110 Older patients with paraplegia and tetraplegia have increased rates of nursing home placement and less neurologic and functional recovery than do younger patients.110
Disuse, Immobilization, and Decompensation
Immobilization has more serious consequences for the elderly than for younger patients. One study showed that even in young men, 29 days of bed rest resulted in a 10% decrease in quadriceps volume and a 16% decrease in gastrocnemius or soleus muscle volume.5 With decreased muscle mass (even when actual sarcopenia is not present), immobilization and disuse of muscles increase the risk in the elderly of weakness sufficient to cause functional problems. In one study involving 10 days of bed rest, 10 healthy older adults (mean age, 67 years) showed a significant decrease in muscle protein synthesis, whole-body lean mass, and lower extremity lean mass, with a greater lean mass loss than younger adults showed after 28 days of bed rest.78 Knee extension strength and stair climbing power decreased after 10 days of bed rest even with a eucaloric diet that provided the “recommended daily” allowance for protein.79 In this study, voluntary physical activity decreased after the 10-day period of bed rest.
In one hospital’s medicine service, low mobility and bed rest in a prospective cohort of 535 patients hospitalized from 1989 to 1991 predicted adverse outcomes. The study team noted that almost 60% of bed rest episodes in the lowest mobility group did not have a documented medical indication.24 Vigilance is needed to prevent the immobilization of elderly patients unless absolutely required by their medical condition. Immobilization also can combine with incontinence, skin fragility, and inadequate nutrition in the elderly to greatly increase the risk for pressure ulcers.
Deconditioning associated with acute hospitalization is not uncommon in the elderly. There are some data supporting inpatient rehabilitation as a tool for enhancing discharges to the community, but not enough data to define the optimal program or site of care.77
Evaluating the Elderly Patient
History Taking
In the outpatient setting, one should ask, “Have you fallen? If so, what were the circumstances?” The person who reports falling on the ice during his or her regular 2-mile walk clearly functions at a different level than the person who falls repeatedly enroute to the bathroom at home. The frequency of falls needs to be determined. The optimal way in which to screen patients to assess fall risk is still under discussion,82 but those who report a fall within the past year are at higher risk for future falls.
Questions about specific activities of daily living (ADLs) are important. Examples include, “Can you get in and out of a bathtub without assistance?” and “How often do you leave home?” Some people identify a functional problem before they bring it to the attention of a health care provider. Patients might have borrowed a cane for perceived gait problems, purchased clothing that is easier to don, or changed their manner of cooking. These are examples of the coping strategies that some elderly patients use to maintain autonomy when they notice difficulties with ADLs or independent living skills.109
Some investigators have attempted to develop additional measures for assessing dangers to the elderly such as fall risk. One study looked at residents in a sheltered accommodation89 who had dementia, stroke, and depression as their most common diagnoses. One finding was that if the resident stopping walking when talking, there was a prediction of a fall within 6 months (positive predictive value, 83%). A prolonged time difference between a walking task with and without carrying a glass of water was shown to identify who is at higher risk for falling among ambulatory elders in a sheltered accommodation who were observed for 6 months.90
The review of systems should include questions about sleep. If sleep is impaired, what is the reason? Sleep management is different if the patient has pain, nocturia, or a mood disorder. Nocturia can result from the nighttime mobilization of peripheral edema.108 Urinary frequency, urgency, and subjective retention need to be identified and treated. If pain is a problem, then as usual one needs to identify factors that precipitate and alleviate symptoms. Urinary incontinence should be excluded as a problem, and the examiner should bring up the topic because patients might be embarrassed about raising the problem.
Is nutrition adequate? If not, is it because of a financial problem, being physically unable to get to a grocery store, being unable to carry food items back from the store, or being afraid of lifting hot items during cooking? One study in 12 elderly women who were observed for 9 weeks showed that inadequate protein intake led to declines in lean tissue mass, muscle function, and immune response.28
The current list of medications should be thoroughly reviewed. Sleeping pills, some antihypertensives (such as β-blockers), metoclopramide, tricyclic antidepressants, and antiseizure drugs can all cause cognitive impairment. Even if the person has been taking the medication for some time, the “tipping point” can be reached when added to other acute health problems. Drug levels considered “therapeutic” can exacerbate a problem such as cognitive impairment in the elderly.108 Nonprescription medications should not be neglected in the history-taking process.53
The history should include a detailed discussion of advanced directives.108 At the time of writing, there is not a single document that is automatically transferred as one moves from facility to facility within the health care system in the United States. Wishes expressed by patients in an office setting to their primary care physician can be unknown to the care providers when a patient is transferred from an acute care hospital to a rehabilitation setting. The legal status of a “living will” varies from state to state. If patients are relying on a health care proxy form to express their wishes, the health care providers should have on hand a copy of the document that stipulates this direction.
Physical Examination
In addition to the standard physical examination, there are useful physiatric additions. If gait problems are present, hip abduction and extension strength might need to be examined while the elderly person is side-lying and prone, respectively. Hip extension range of motion should be assessed. If deficits in position sense are present, it should be determined whether they are only at the great toe or also at the ankle. The Achilles muscle stretch reflex will be absent in some elderly individuals.108 Vibratory loss is typically more sensitive than position sense in picking up neuropathy.131 Cerebellar testing should include both finger-to-nose and heel-to-shin procedures. However, in patients with limitations of hip range of motion, it might not be possible for them to actually bring the heel up to the shin at the knee.
Formal mental status screening can be done with tests such as the Mini-Mental Status Examination of Folstein.6 A baseline mild dementia can be masked when the person is in the familiar home setting, but becomes noticeable when admitted to the hospital.
The range-of-motion examination is very important in the elderly. Even relatively minor losses in range of motion can affect function. The range of motion of the neck and shoulders should be thoroughly checked. Loss of shoulder internal rotation makes it difficult for the patient to get the hands to the back, as in attaching a bra strap. Loss of shoulder external rotation makes it difficult to get the hands to the top of the head for hair care. Wrist extension and flexion, and finger flexion and extension limitations can have important functional ramifications in many activities that require manual dexterity.
There is not yet consensus on the best test to use in the clinic setting for functional mobility. The “Get Up and Go” test looks for unsteadiness as the person gets up from a chair without using the upper limbs, walks a few meters and returns.132 The Berg Balance Scale looks at 14 items on a scale from 0 to 4, assessing the ability to maintain static balance and while in functional positions.18,32,96
Laboratory Assessment
A discussion of the full range of potential testing is beyond the scope of this chapter. As the physiatrist, one should bear in the mind that certain nutritional deficiencies (such as vitamin B12 or vitamin D) can be more common in the elderly. Also, some elderly patients might not be aware of episodes of loss of consciousness. Consider that syncope might be occurring if the patient reports falls without known precipitants.131 A bone density scan can influence decision making for the primary care physician as to osteoporosis treatment and prevention.
Management Issues in the Elderly
Medication Usage in the Elderly
Medication use in the elderly must be judicious because of the changes in drug metabolism that occur with age. The reactions of the elderly to medications are not always the same as those of the population that was used to initially test the medication. Polypharmacy is a concern because the number of potential interactions increases as more medications are used. Compliance with a medication program can be a problem because of the complexity of the regimen proposed, the cost of the medication, and the cognitive status of the patient. Adverse effects of medications can be more severe in the elderly population.33 Elderly individuals as a group have traditionally been less represented in clinical drug trials.33 Therefore it should be kept in mind that new signs and symptoms can be an adverse effect of treatment rather than a new condition.
The treatment plan for an elderly patient has to be realistic. It is better to work with the patient to design a medication schedule that can actually be carried out, rather than to devise a plan that will work only under optimal conditions. This is particularly important if something completely new is being introduced to the patient, such as expecting a person with new diabetes and limited vision to learn to adjust insulin, check blood glucose levels four times a day, and change food preparation habits within a very short time. In a study by Kaufman et al.,73 in ambulatory adult women older than 65 years, 12% had taken at least 10 different types of medications during the preceding week (including nonprescription medications or supplements), and 81% had taken at least one prescription medicine during the preceding week. In the same study, 71% of men 65 years or older had taken at least one prescription drug, and 19% had taken five or more during the preceding week.73
The increase in adipose tissue that typically occurs with age causes a larger volume of distribution for fat-soluble drugs and prolongs their biologic half-life.29 Conversely, total body water decreases by as much as 15% between 20 and 80 years of age, which decreases the volume of distribution of water-soluble drugs and thus results in a higher serum concentration.29 Because drug elimination is so affected by renal function, it is wise to check drug levels29 when drugs with a low therapeutic index and significant renal clearance are prescribed. Confusion, sedation, nausea, change in bowel habits, and balance problems are symptoms that can be confused with a new illness rather than as adverse reaction to medications. A serious error in treatment can occur when additional medications are added to treat what was actually an adverse reaction to medication.29 The reported incidence of adverse drug reactions in the elderly is 20% to 25%.29