Burden of illness associated with painful diabetic peripheral neuropathy among adults seeking treatment in the US: results from a retrospective chart review and cross-sectional survey

Abstract

Background: The purpose of this study was to characterize the burden of illness among adult subjects with painful diabetic peripheral neuropathy (pDPN) seeking treatment in the US.

Methods: This observational study recruited 112 subjects with pDPN during routine visits from general practitioner and specialist sites. Subjects completed a one-time questionnaire, which included demographics, symptom duration, health care resource use, out-of-pocket costs, employment status, and validated measures that assessed pain, functioning, sleep, anxiety and depression, health status, and productivity. Investigators completed a case report form based on a 6-month retrospective chart review to capture clinical information, pDPN-related treatments, and other pDPN-related health care resource use over the past 6 months. Annualized costs were extrapolated based on reported 6-month health care resource use.

Results: The mean age of the subjects was 61.1 years, 52.7% were female, and 17.9% were in paid employment. The most common comorbid conditions were sleep disturbance/insomnia (43.8%), depressive symptoms (41.1%), and anxiety (35.7%). The mean pain severity score was 5.2 (0-10 scale), and 79.5% reported moderate or severe pain. The mean pain interference with function score was 5.0 (0-10 scale) overall, with 2.0 among mild, 5.1 among moderate, and 7.0 among severe. The mean Medical Outcomes Study sleep problems index score was 48.5 (0-100 scale). The mean health state utility score was 0.61. Among subjects employed for pay, mean overall work impairment was 43.6%. Across all subjects, mean overall activity impairment was 52.3%. In total, 81.3% were prescribed at least one medication for their pDPN; 50.9% reported taking at least one nonprescription medication. Adjusted mean annualized total direct and indirect costs per subject were $4841 and $9730, respectively. Outcomes related to pain interference with function, sleep, health status, activity impairment, prescription medication use, and direct and indirect costs were significantly worse among subjects with more severe pain (P < 0.0020).

Conclusion: Subjects with pDPN exhibited high pain levels, which were associated with poor sleep, function, and productivity. Health care resource utilization in pDPN was prevalent and costs increased with greater pain severity. The burden of pDPN was greater among subjects with greater pain severity.

Keywords: burden of illness; costs; health care resource use; pain assessment; painful diabetic peripheral neuropathy; productivity; quality of life; treatment patterns.

Figure 1

Comorbidities among pDPN subjects, by average pain severity.* Notes: *Scores on the BPI Pain Severity were used to classify average pain severity as follows: 0–3 represents mild pain, 4–6 represents moderate pain, and 7–10 represents severe pain; ^‡proportion of pDPN subjects with Headache/migraine significantly different by pain severity (P = 0.0001); ^†proportion of pDPN subjects with Chronic Low Back Pain significantly different by pain severity (P = 0.0027).

Figure 2A

SF-12 physical and mental component summary scores, overall and by average pain severity.* Notes: *Scores on the BPI Pain Severity were used to classify average pain severity as follows: 0–3 represents mild pain, 4–6 represents moderate pain, and 7–10 represents severe pain; ^†P < 0.0001 for both PCS and MCS. All domains [physical function, role physical, bodily pain, general health, vitality, social functioning, role emotional, mental health] including PCS and MCS significantly different by average pain severity (P < 0.001).

Figure 2B

Pain interference with function, overall and by average pain severity.* Notes: *Scores on the BPI Pain Severity were used to classify average pain severity as follows: 0–3 represents mild pain, 4–6 represents moderate pain, and 7–10 represents severe pain; ^†P < 0.0001 for BPISF Pain Interference Index by pain severity. All domains [general activity, mood, walking ability, normal work, relations with other people, sleep, and enjoyment of life] significantly different by average pain severity (P < 0.0001).

Figure 2C

MOS-SS overall sleep index, overall and by average pain severity.* Notes: *Scores on the BPI Pain Severity were used to classify average pain severity as follows: 0–3 represents mild pain, 4–6 represents moderate pain, and 7–10 represents severe pain; ^†P < 0.0001 for Overall Sleep Index by pain severity. All domains [sleep disturbance, sleep adequacy, sleep somnolence, snoring, shortness of breath or headache, sleep quantity] significantly different by average pain severity (P < 0.05).

Figure 3A

Proportion of pDPN subjects taking prescription medications for pDPN, overall and by average pain severity.* Notes: *Scores on the BPI Pain Severity were used to classify average pain severity as follows: 0–3 represents mild pain, 4–6 represents moderate pain, and 7–10 represents severe pain; ^†proportion of pDPN subjects taking prescription medications for their pDPN significantly different by pain severity (P = 0.0004).

Figure 3B

Use of prescription treatments for pDPN, overall.* Notes: *Subjects may be taking more than one class of prescription medication; ^†Weak SOA, Strong SAO, and LAO were also collapsed into “All Opioids” class; proportion prescribed = 33.0% overall, 9.1% mild, 31.6% moderate, 53.1% severe (P = 0.0027). Abbreviations: AEDs, antiepileptics; SAO, strong-acting opioids; NSAIDs, nonsteroidal anti-inflammatory drugs; LAO, long-acting opioids; SNRIs, Serotonin–norepinephrine reuptake inhibitors; TCAs, tricyclic antidepressants; SSRI, selective serotonin re-uptake inhibitors.

Figure 4

Adjusted average annualized cost per pDPN subject, overall and by average pain severity.* Notes: *Scores on the BPI Pain Severity were used to classify average pain severity as follows: 0–3 represents mild pain, 4–6 represents moderate pain, and 7–10 represents severe pain; ^†average annualized total direct cost per pDPN subject was significantly different by pain severity (P < 0.0001). Direct costs include physician visits, other healthcare provider visits, prescription medications, TENS device, outpatient tests/procedures, emergency room visits, hospital outpatient visits, hospitalizations, direct medical costs to subjects, and direct non-medical (child care, help with house and/or yard work, and help with activities of daily living) due to pDPN; ^‡average annualized total indirect cost per pDPN subject was significantly different by pain severity (P = 0.0003). Total indirect costs include overall work impairment, activity impairment, disability, unemployment, early retirement, and reduced work schedule due to pDPN; ^§adjusted LS mean estimates from multiple linear regression adjusted for confounding demographic and clinical variables. Covariates included in adjusting direct costs: race, pain severity (mild/moderate/severe only), employment status, worker’s compensation, and comorbidities (depressive symptoms, headache/migraine, fibromyalgia [mild/moderate/severe only], chronic fatigue syndrome [overall only], and chronic low back pain); covariates included in adjusting indirect costs: sex, race, pain severity, employment status, worker’s compensation, and comorbidities (major depressive disorder and Raynaud’s syndrome).