Elderly men and women represent the fastest-growing segment of the population. In the United States, the number of people aged 65 and older is projected to grow to almost 80 million by 2040. Chronic pain is a growing problem in this increasingly aging population, as the incidence and prevalence of pain increase with age. It is estimated that up to 50% of older adults living in the community and 80% of elderly living in long-term care facilities experience chronic pain.¹

Pain in the elderly is undertreated as a result of inadequate recognition, assessment, and management. Presentation of pain is often atypical, complex, and multifactorial. Pain often remains undetected, as the elderly often underreport symptoms or caretakers fail to adequately assess or recognize signs of pain.^1,2 Cognitive decline and communication difficulties further complicate proper assessment.³ Management of pain is complicated by the lack of geriatric pain education for providers and reluctance to use potentially addictive medications. Multiple studies confirm undertreatment of pain in nursing homes and the community.⁴

Uncontrolled pain can result in significant physical and social consequences. Persistent pain may lead to functional loss, including impaired mobility and activities of daily living (ADLs), and generally reduced quality of life. Elderly with untreated pain may have exacerbation of cognitive impairment, mental health issues such as depression and anxiety, sleep disturbance, and social withdrawal.^5,6 Inadequately controlled pain has significant socioeconomic consequences, including increased utilization of health care resources and financial costs, that will surely increase as this population segment continues to grow. Despite these difficulties, pain in the elderly is better managed through physician education, comprehensive multidisciplinary assessment, and the use of proper pharmacologic and nonpharmacologic management strategies.

Many elderly individuals experience pain with their ADLs.⁷ Older individuals may experience more pain with age because they are undertreated; patients who appear frail or have several comorbidities have been shown to receive inadequate medication. Reasons for this include unfamiliarity with treating this population and with medication side effect profiles. Another contributing factor is the poor recognition of pain by pain screening tools or scales. The visual analog scale (VAS) has been reported to be less accurate in geriatric patient screening.⁸ Other tests have been shown to be inconsistent as well. Measuring intensity of chronic arthritic pain can give conflicting results regarding age differences on several one-dimensional scales, depending on the screening test.⁸

Pain complaints in the older population are more likely to be due to an underlying problem (i.e., malignancy, progressive spinal stenosis) as opposed to an acute issue. A caregiver may easily overlook a complaint as a “chronic issue” and not investigate any further. The patient may also attribute their daily pain to old age and accept it as a regular part of aging and not seek any pain-alleviating interventions. Speech and cognition can also present a barrier, and the physician must look for facial expressions that may be conveying pain or discomfort.

Studies on pain thresholds have been inconsistent in evaluating the relationship between pain and age.⁹ These differences may be due to the Aδ and C fiber deterioration and in their transmission of pain signals. In addition to physical pain, grief, anxiety, and social problems contribute to the psychological pain that affects the geriatric population.

It is estimated that by the year 2025, approximately 1.2 billion people worldwide will be older than 60 and roughly 50% of elderly patients will report chronic pain.¹⁰ Unfortunately, studies that solely focus on pain in the geriatric population are limited. Most epidemiological studies of pain in older people were not designed with the primary objective of examining the problem of pain.¹¹ Some studies show a direct correlation between increasing age and pain, but similar studies have had mixed results.¹² There may be a peak or a plateau in the prevalence of pain by age 65 and a decline in reported pain in the 75 and older population.¹¹

Methods used to evaluate the intricacies of pain include self-reporting, pain behavior, and measurement of psychophysical parameters.¹³ Self-reporting is most often used, but it can be difficult to evaluate the older patient because of the high intervariability and seemingly nonoptimal questionnaires. For example, one nursing home study found a strong intergeriatrician agreement with pain assessment of mild/moderate pain but a weaker correlation within the severe pain population.¹⁴ The most common of these pain complaints are due to osteoarthritis (OA), peripheral diabetic neuropathy, postherpetic neuralgia, malignancies, spinal stenosis, and pain resulting from cerebrovascular accident (CVA).⁷ Emotional pain can also manifest itself as a concurrent or independent generator of pain.

Numerous physiological changes alter pain perception. Pain is primarily transmitted through the Aδ and C fibers, but with age, the number of fibers decreases, making these stimuli harder to detect. This in turn decreases the pain threshold. Cortical recognition in the central nervous system (CNS) has also been shown to retard with age, adding to the impairment of the ability to localize and report pain.⁷

Additionally, dementia and cortical/neuronal atrophy become more prevalent with age. Other changes have also been observed, including a reduction in both β-endorphin content and gamma aminobutyric acid (GABA) synthesis in the lateral thalamus, a decline in the concentration of central GABA and serotonin receptors, a decrease in the speed of the nociceptive process, and a decline in the C and Aδ fiber function.¹⁵ Sleep disturbances may also manifest. Older patients are more likely to have difficulty falling asleep, staying asleep, and receive less rapid eye movement (REM) sleep. Cognitive slowing and memory impairment have also been noted with progression of age.

Drug Pharmacokinetics

Medication metabolism changes with increasing age. This is attributed to changes in the metabolism and clearance rates of drugs and leads to altered pharmacokinetics and pharmacodynamics.⁸ The body content of fat, muscle, and water balance play an integral role in a medicine’s effect, but the proportions of these change with time. Malnutrition, malignancy, psychological effect, and community mobility also contribute to these changes.

With age, muscle mass decreases and adipose mass increases. These changes affect the circulation and elimination properties of medications. Lipophilic drugs’ pharmacokinetic properties are adipose dependent and can produce variable efficacies in this population. Cardiac issues are routinely found in the elderly population and are commonly treated with diuretics, which alter the body’s water content. Albumin production is diminished, with malnourishment and chronic liver disease affecting the binding with various medications. Geriatric patients exhibit increased sensitivity to drugs that act centrally or have centrally mediated effects, including benzodiazepines, opioids, and psychotropic drugs.⁹ In contrast, the adrenergic and cholinergic autonomic nervous system has reduced sensitivity to receptor-specific drugs, as well as a reduced response to β-adrenergic stimulation that decreases the effect of β-blockers.⁹ Lastly, some medications are common to this population (i.e., steroids for chronic obstructive pulmonary disease [COPD] and aspirin for cardiovascular issues) where drug–drug interactions are unavoidable.

Comorbidities

The geriatric population has more comorbidities than younger populations. Some of the most common comorbidities contributing to pain found in the elderly include rheumatic diseases, cancer, angina, herpes zoster, shingles, temporal arteritis, diabetes-related peripheral neuropathy, trigeminal neuralgia, alcohol abuse, and malnutrition.⁹ Though less common than the aforementioned issues, gastrointestinal issues are higher in the geriatric population compared to younger populations and can dually cause pain and can be troublesome with nonsteroidal anti- inflammatory drug (NSAID) use. Sleep disturbances are also more common in the older population.

Aging of Organ Systems

All patients should undergo routine physical examinations and laboratory studies to ensure proper organ function, which may deteriorate with age. Even relatively healthy geriatric adults experience physiological changes. Brain magnetic resonance imaging (MRI) in the elderly population has demonstrated lower activity of structures involving pain processing, such as in the contralateral caudate and putamen.¹⁰

The liver mass, blood flow, and decrease of the CYP-450 enzymes reduce the drug elimination clearance rate of the liver, especially with chronic disease.¹⁰ Long-term alcohol abuse can cause cirrhosis. Additionally, with age there is noted decrease in demethylation (affecting benzodiazepine metabolism), decreased albumin production, decreased liver regeneration and capacity, and decreased hepatic blood flow.⁹

Regarding renal function, the glomerular filtration rate (GFR) of the kidneys decreases with age at a rate of 1% per year starting at age 40.^9,10 This rate can increase with any associated chronic renal disease. Anatomic changes to kidneys include decreased size by 25% by age 70, decreased number and thickness of renal tubules, decreased renal blood flow, and decreased free water absorption of 5% per decade after 50.⁹

Gastrointestinal motility, secretions, blood flow, and absorptive surface decrease with age.¹⁰ This can lead to constipation, poor appetite, and abdominal pain. Musculoskeletal disorders are also more prevalent with age. Degenerative changes such as OA and lumbar spinal stenosis are common sources of aches, stiffness, and pain exacerbated with activity, which can limit ADLs. Osteoporosis, coupled with the aforementioned musculoskeletal issues, can amplify pain and debility.

Cardiac issues, including coronary artery disease and chronic heart failure, increase in proportion as one ages. There is also a higher propensity of exacerbating cardiac issues with various medications (i.e., tricyclic antidepressants causing arrhythmias) in this population that requires close observation.

Lastly, profound changes occur with age in the peripheral and central nervous systems. These include a decrease in the density of peripheral nerves and loss of neurons in the dorsal horn and thalamus (Table 41–1).

Depression

There is a paucity of data evaluating pain in the cognitively impaired population. Studies have demonstrated confounding results with the correlation between chronic pain and depression. One study reported that there are no age differences in severity or prevalence of depressive symptoms experienced by chronic pain patients.⁸ Another study showed a significant increase in depressive symptoms in older adults with pain; furthermore, a strong association between chronic pain and depression was identified (12.4% in the younger population vs. 47.5% in those older than 70).¹⁶ There is also a significant correlation between pain and depression among nursing home residents, even after controlling for self-reported functional status and physical health.¹⁴ Analgesics, therapies, and family and community support are all important tools in circumventing depression and the sequelae, and are vital safety nets for patients to ensure strong mental health.

Not only does the geriatric population report more pain sites, they are also more descriptive, using a larger number of pain adjectives.¹⁶ Conditions such as osteoarthritis and fibromyalgia have demonstrated a correlation between aging and increased pain—especially in the feet, knees, and lower back.⁸ Regarding low back pain, there is no consensus whether back pain is directly correlated with age. With chronic low back pain in the geriatric population, there is an associated decrease in functional reach and repetitive trunk rotation.¹⁷ Headaches appear to be less of a pain generator as one ages. Edentulism increases with age but appears to be a lesser cause of pain than in the younger and middle-aged population.

Differences with regard to the incidence and experience of pain exist between genders. Women have a longer life expectancy and thus comprise a larger portion of the geriatric population. Generally speaking, women are more likely to experience rheumatologic conditions, headache complaints, and fibromyalgia. About 7% of women between 60 and 79 have been diagnosed with fibromyalgia.¹⁸ Men have been found to have a higher incidence of spondyloarthropathies and chronic low back pain.¹¹ Complaints of headaches and abdominal pain appear similar between genders.¹¹

Many clinicians lack formal pain education training, as there is little emphasis in medical school and most residency training programs.^19,20 Limited time is solely devoted to topics in pain medicine, but rather integrated into established curricula. Although geriatric fellowships recognize chronic pain management as an essential component of comprehensive training, research shows that the actual training is inadequate.²¹ A survey of U.S. geriatric medicine fellowship programs identified multiple areas of educational deficiency, notably assessment of musculoskeletal and neuropathic pain, pharmacologic and nonpharmacologic treatments of chronic pain, and the role of multidisciplinary pain clinics in pain management.²²

Undereducating physicians likely is a partial reason for undertreatment of pain in the geriatric population. Although recent improvements have been made, development and incorporation of a formal and systematic geriatric pain education curriculum during medical school, residency, and fellowship training are essential to improving patient care and preventing progressive functional and psychological impairments.^23,24

A comprehensive assessment is critical to effective management of pain in the elderly. This is challenging, as elderly adults may perceive pain differently, have misconceptions regarding pain, and conceal or fail to report pain altogether.²⁵ They may recognize “hurt,” “ache,” or “discomfort” but not associate these sensations with “pain.” Some individuals accept pain as an inevitable and expected part of aging, or assume that complete pain relief is unavailable or unattainable. Others worry that reporting pain will lead to further difficult diagnostic workups or fear treatment with potentially addictive analgesics with adverse side effects.

Pain is a subjective complaint, and self-reporting of pain presence and intensity can be accurate and reliable, even in patients with mild to moderate cognitive impairment.²⁶ Selection of an appropriate diagnostic screening tool or scale can assist with evaluation. A numerical rating scale (NRS), asking the patient “on a scale of 0 to 10, how severe is your pain?” is commonly used as an initial assessment. The elderly may have difficulty with this, especially when administered verbally, and it may be necessary to use other one-dimensional scales to evaluate pain intensity.²⁷ Unidimensional scales are often used in the geriatric population (Table 41–2).

The verbal descriptor scale (VDS) is an effective measure of pain intensity as well. The VAS, a 10-cm line where the patient is instructed to indicate at which point along the line best represents his or her current pain level, is classically used. However, increasing age is associated with a higher frequency of incorrect responses.²⁸ Using a vertical orientation of VAS, such as a pain thermometer or faces scale, may be more appropriate^29,30 (Fig. 41–1).

Multidimensional scales are also valuable to evaluate patient experience of pain (Table 41–3).

The McGill Pain Questionnaire (MPQ) is used to assess sensory, affective, evaluative, temporal, and miscellaneous qualities of pain; however, it has been noted to be long and complicated.³¹ In this questionnaire, the patient selects adjectives to describe current pain. A short form of the MPQ (SF-MPQ) also includes a VAS to measure intensity and may be more appropriate.^31,32 There is a significant correlation of sensory and affective scales on the SF-MPQ, as well as on the VDS and VAS.³³

A thorough assessment requires a complete history and physical examination, focusing on the patient’s main pain complaints. It is important to screen for cognitive impairment, depression, and impact of pain on sleep. Decreased function in terms of mobility and ADLs may also suggest underlying pain.^9,34 Input and reports from family, therapists, mental health providers, and other health care professionals can be reliable sources of pain reporting, especially in the nonverbal or cognitively impaired. Interdisciplinary assessment from other medical specialties may be helpful to identify potentially treatable co-factors.

Cognitively Impaired

Proper assessment and treatment of pain are particularly challenging in the elderly patient with dementia or cognitive impairment. In nursing home patient pain evaluation, there is a strong intergeriatrician agreement with assessment of the mild/moderate cognitively impaired but a weaker correlation within the severely cognitively impaired.¹⁴ These patients are among the most undertreated, yet they may suffer the most severe pain. In nursing home patients, individuals with dementia have significantly more pain, yet receive less pain analgesia than the cognitively healthy.³⁵

There is no systematically accepted pain assessment tool for cognitively impaired patients in the hospital or long-term care facilities. Self-reporting of pain is reliable in mild to moderate cognitive impairment. Use of a VDS has also been found to be appropriate.^28,36 In patients with more severe impairment, clinicians must rely on their own or other caregiver perception of the patient’s pain. These patients often cannot communicate their pain perception, and it is essential to observe and examine behavioral changes that may reflect underlying pain.³⁷ Potential behavioral cues include facial expressions, verbalizations or vocalizations, body movements, appetite, sleep changes, and other mental status changes. Other behavioral assessment scales have been suggested; however, it is unknown how well they have been incorporated into practice.^13,38,39