Consequences of Neuropathic Pain: Quality-of-life Issues and Associated Costs

Pain is the primary reason for patients seeking healthcare, and it has been estimated to result in more than $100 billion per year in direct medical costs. Neuropathic pain (NP) alone has been associated with an approximately 3-fold increase in use of healthcare resources. The indirect costs associated with chronic pain result from increased absenteeism and decreased productivity at work, and they also have been estimated to total $100 billion each year in the United States. NP contributes substantially to these costs. Results from one study indicated that employment was affected in 43% of patients with NP. Quality of life is also significantly reduced in such patients. Patients with chronic pain also have difficulty in initiating and maintaining sleep, and sleep deprivation has the potential to exacerbate pain. Sleep deprivation is also associated with both anxiety and depression, and both of these conditions can exacerbate sleep disturbances. Effective management of the patient with chronic pain, including NP, requires assessment and, if necessary, treatment of all comorbidities associated with this condition.

(Am J Manag Care. 2006;12:S263-S268)

Chronic pain results in high societal and patient burden. It has been estimated that 50 million people in the United States suffer from chronic pain, and it is the number one cause of disability in this country.¹ Results compiled by the American Pain Foundation (APF) document the high prevalence of chronic pain in the United States. Estimates from a large number of surveys reviewed by the APF indicate that 89% of people in the United States have some pain at least monthly and that nearly 26 million Americans suffer from severe pain. People with moderate-to-severe pain have lived with their pain for an average of almost 1.5 years.² This article reviews the impact of chronic pain and neuropathic pain (NP) on society and individual patients.

IMPACT OF PAIN ON SOCIETY

The cost of pain or any other condition to society is generally divided into 2 parts: the direct costs associated with disease management and the indirect costs resulting from reduced productivity and worker absenteeism.

Direct Costs of Chronic Pain Management

The Centers for Disease Control and Prevention has estimated that total healthcare costs in the United States are $1.4 trillion annually.³ Management of chronic pain contributes significantly to this total cost. Pain is the primary reason for seeking healthcare, and the direct medical costs for treatment of both acute and chronic pain have been estimated to exceed $100 billion per year.⁴ Although total direct medical costs associated with all types of NP are not available, Berger and colleagues have provided an estimate of the excess direct medical treatment cost in people with NP.⁵ These investigators carried out a matched case-control study that included 55 686 patients with NP, most often back and neck pain with neuropathic involvement (62.3%), causalgia (12.1%), and diabetic peripheral neuropathy (DPN) (10.8%). Subjects with NP included in this study were more likely than controls to have other pain-related conditions and comorbidities, including fibromyalgia (6.0% vs 0.6% for control subjects), osteoarthritis (13.6% vs 3.6%), coronary heart disease (13.6% vs 6.5%), and depression (6.4% vs 2.3%). In the 2000 calendar year, total healthcare charges for patients with NP were $17 355 versus $5715 for controls.⁵ Thus, the presence of NP in a large cohort of patients is associated with an approximate 3-fold increase in healthcare costs versus those without NP.

Gordois and colleagues have provided information about the costs associated with DPN, a common cause of NP. Their results indicated that the total annual direct medical costs for the treatment of DPN and its complications were $10.91 billion.⁶

Indirect Costs of Chronic Pain

The indirect costs associated with chronic pain have been estimated to total $100 billion each year in the United States.¹ Both absenteeism and presenteeism (reduced productivity while at work) contribute to this cost.

The American Productivity Audit, a national survey of the United States workforce, was completed in 2002. This cross-sectional study was used to measure lost productive time associated with pain over a 2-week period in the summer of 2001. Survey results showed that 13% of the total workforce experienced a loss in productive time during a 2-week period as a result of pain. Workers who experienced lost productive time from a pain condition lost a mean of 4.6 hours per week. No difference in the proportion of the workforce losing =2 hours/week due to pain was observed as a function of subject sex, age, region of residence, type of occupation, duration of time in job, month of interview, or health insurance status. The majority (76.6%) of the lost productive time was explained by reduced performance while at work rather than absence. Lost productive time from common pain conditions among active workers costs an estimated $61.2 billion per year. This amount accounts for 27% of the total estimated work-related cost of pain conditions in the United States workforce.⁷ These results are consistent with other findings reported by the APF, which indicated that more than two thirds of all full-time employees (68%), the equivalent of more than 80 million workers, suffer from pain-related conditions. In addition, 14% of all full-time employees (>17 million) took sick days in 1995 as a result of pain conditions, which resulted in more than 50 million lost work days.²

Additional analysis of a subset of 391 respondents in the American Productivity Audit with self-reported DPN indicated greater losses of productivity for this group than for either controls or participants with diabetes but without DPN. Approximately 28% of subjects without diabetes lost =2 hours per 2 workweeks as a result of health-related causes. The respective values for subjects with diabetes only and diabetes plus DPN were 34% and 52%.⁸

Results from a smaller-scale study of patients with painful DPN also indicated that this condition results in lost productivity to at least the same degree as all types of chronic pain considered together. About one third of the 140 subjects included in this survey (35%) reported some level of disruption in their employment status due to painful DPN, including reduced work time (15%), disability (12%), or becoming unemployed or taking early retirement (8%). Among those who were working for pay at the time of the survey, 59% reported being less productive at work at least some of the time.⁹ These results are consistent with those from a larger sample of 602 patients with NP who were recruited from general practitioners in 6 European countries. Employment status was affected in 43% of patients, and those who were employed missed a mean of 5.5 workdays during the past month.¹⁰

IMPACT OF CHRONIC PAIN ON QUALITY OF LIFE

Results from numerous studies have demonstrated that chronic pain and NP both have significant negative effects on all quality- of-life domains. For example, Becker and colleagues evaluated 150 patients with chronic nonmalignant pain (46% with NP) and noted that these patients were significantly below population norms for all domains of the Medical Outcome Study- Short Form (SF)-36 (Figure).¹¹ This was also the case for all Psychological General Well-being subscores.

Vinik and colleagues have demonstrated that quality of life is significantly reduced in patients with painful DPN. They used the Norfolk Quality of Life Questionnaire- Diabetic Neuropathy to compare 262 patients with painful DPN, 86 patients with diabetes but without DPN, and 81 healthy controls. Study results indicated differences between patients with DPN and both control groups for all item groupings. Results also showed that total quality-of-life scores correlated with severity of neuropathy.¹²

Benbow and associates also reported reduced quality of life in a comparison of 79 people with type 1 and type 2 diabetes versus 37 nondiabetic controls who were assessed using the Nottingham Health Profile (NHP). Subjects with neuropathy had significantly reduced quality of life in 5 of 6 NHP domains versus patients with diabetes but without DPN and healthy controls. The domains significantly affected by DPN were emotional reaction, energy, pain, physical mobility, and sleep.¹³

A prospective study of 105 patients with painful DPN also indicated significant negative impact of this condition on quality of life (Table 1). Results obtained using the Brief Pain Inventory indicated that pain substantially interfered with sleep (57.1% of patients), enjoyment of life (58.2%), recreational activities (56.1%), general activity (48.0%), mobility (57.0%), normal work (56.6%), and social activity (50.5%).¹⁴

COMORBIDITIES IN PATIENTS WITH CHRONIC PAIN

As noted, people with NP are more likely than people without NP to have comorbidities, which include coronary heart disease and depression.⁵ Patients with NP are also likely to have increased anxiety and pain-associated interference with sleep.^15-17 The combination of pain, interference with sleep, depression, and anxiety can greatly interfere with patients' ability to function.

Sleep Deprivation

Sleep deprivation can be particularly devastating in patients with chronic pain, who often have difficulty initiating and maintaining sleep. Sleep deprivation has been associated with a decreased pain threshold, muscle aches, and stiffness in normal volunteers, and loss of sleep might thus be expected to exacerbate the underlying cause of sleep deprivation in patients with chronic pain. Sleep deprivation has also been associated with both anxiety and depression, and both of these conditions can, in turn, result in sleep disturbances.¹⁸ Loss of sleep can influence the prognosis for many diseases, and sleep deprivation has been shown to increase the risk for impaired glucose tolerance and diabetes.¹⁹

MANAGING THE WHOLE PATIENT WITH CHRONIC PAIN

Effective management of the patient with chronic pain, including NP, requires assessment and, if necessary, treatment of all comorbidities associated with this condition. Physicians should evaluate all aspects of pain, sleep, and mood in patients with chronic pain. Several instruments have been developed to aid clinicians in gathering qualitative and quantitative information from patients with chronic pain. These include the Pittsburgh Sleep Quality Index, Hamilton Depression Rating Scale, Beck Depression Inventory (BDI), SF-36, NHP, and Treatment Outcome for Pain Survey, a version of the SF-36 specifically developed for pain clinics. A sleep diary is also a reliable approach to obtaining information about sleep disturbance in patients with chronic pain.¹⁸

All patients with chronic pain should be screened for depression with a simple instrument, such as the BDI. A preliminary screen for depression can be accomplished by asking 2 simple questions: (1) During the past month, have you often been bothered by feeling down, depressed, or hopeless? and (2) During the past month, have you often been bothered by having little interest or pleasure in doing things?¹⁸

The triad of chronic pain, sleep disturbances, and depression/anxiety is particularly important and must be fully addressed if the patient is to be restored to optimal functionality. Pharmacologic treatment strategies that reduce pain frequently result in concurrent improvements in common pain-associated comorbidities, and therapy should be selected on the basis of its impact both on pain and on these conditions.²⁰

Effective treatment of pain can significantly improve quality of life, and clinical trial results for at least some agents that have been approved for the treatment of NP and DPN document this. Duloxetine, gabapentin, and pregabalin have all been shown to improve quality of life in patients with NP,^21-23 and both gabapentin and pregabalin have also been demonstrated to improve sleep in patients with NP.^22,23 Results from these and a selection of other studies that evaluated effects of medical therapy on quality of life in patients with DPN or postherpetic neuralgia (PHN) are summarized in Table 2.

CONCLUSION

Effective treatment that addresses pain and comorbidities can enhance outcomes for patients with chronic pain. Some agents used for the treatment of NP, particularly newer medications approved for painful DPN and PHN, have the potential to produce improvements in pain and comorbidities, particularly sleep disturbance, and to enhance quality of life. Even the most effective therapies may not provide complete pain relief in many patients with NP, and a better measure of treatment outcome may be improvements in functionality and quality of life, which reflect the impact of treatment on a wide range of variables.

Address Correspondence to: Bill McCarberg, MD, Chronic Pain Management Program, Kaiser Permanente, 732 North Broadway, Escondido, CA 92025. E-mail: bill.h.mccarberg@kp.org.

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