title: Relationship between pain relief and improvements in patient function/quality of life in patients with painful diabetic peripheral neuropathy or postherpetic neuralgia treated with pregabalin.
abstract: BACKGROUND
  In patients with chronic pain due to diabetic peripheral neuropathy (DPN) or postherpetic neuralgia (PHN), pregabalin treatment results in pain relief and improved patient function/quality of life (QoL). Few studies, however, have examined the exact relationship between pain relief and improvements in patient function/QoL. It is unclear, for example, whether pregabalin has a direct independent effect on patient function/QoL or whether improvements in function/QoL are an indirect consequent of pain relief.
  
  
  OBJECTIVE
  To determine whether improvements in function/QoL in response to pregabalin treatment are related to the extent of pain relief in patients with neuropathic pain due to DPN or PHN and to determine whether pregabalin has a direct independent effect on patient function/QoL that is distinct from its effects on pain.
  
  
  METHODS
  Data from 11 randomized, double-blind, placebo-controlled trials of pregabalin for the treatment of DPN or PHN were pooled for this analysis. Changes in patient function/QoL scores were plotted according to the extent of pain relief to assess whether greater levels of pain relief were associated with greater improvement in function/QoL. A novel mediation analysis was used to asses to what extent the effects of pregabalin on function/QoL scores are a direct treatment effect as opposed to an indirect effect mediated through improvements in pain or sleep.
  
  
  RESULTS
  Moderate-to-substantial pain relief (a ≥30% decrease in pain) in response to pregabalin treatment was associated with significant (P < 0.05) improvements in 36-Item Short Form Health Survey (SF-36) scores (used to assess patient function/QoL). In many patients, greatest improvement in SF-36 scores was reported by patients achieving ≥50% decrease in pain. Analysis of Patient Global Impression of Change scores revealed a similar trend, where >80% of patients who achieved substantial pain relief also reported their status as much or very much improved. A substantial direct pregabalin treatment effect was evident for many SF-36 domains that could not be explained by pain relief or improvement in sleep.
  
  
  CONCLUSIONS
  In patients with chronic pain due to DPN or PHN, improvements in patient function/QoL in response to pregabalin treatment are correlated with the extent of pain relief. However, such improvements in function/QoL are not mediated entirely through pain relief but are the result of a combination of pregabalin's effects on pain and sleep disturbance and a direct effect on patient function itself.
authors.affiliation: Department of Internal Medicine, Eastern Virginia Medical School, Norfolk, VA, USA. VinikAI@evms.edu
authors.forename: Aaron
authors.initials: A
authors.lastname: Vinik
authors.forename: Birol
authors.initials: B
authors.lastname: Emir
authors.forename: Raymond
authors.initials: R
authors.lastname: Cheung
authors.forename: Ed
authors.initials: E
authors.lastname: Whalen
mesh_terms: D000700:Analgesics / Q000627:therapeutic use; D003929:Diabetic Neuropathies / Q000188:drug therapy* / Q000503:physiopathology; D006306:Health Surveys; D006801:Humans; D051474:Neuralgia, Postherpetic / Q000188:drug therapy* / Q000503:physiopathology; D000069583:Pregabalin; D011788:Quality of Life; D016032:Randomized Controlled Trials as Topic; D012893:Sleep Wake Disorders / Q000188:drug therapy / Q000209:etiology; D016896:Treatment Outcome; D005680:gamma-Aminobutyric Acid / Q000031:analogs & derivatives* / Q000627:therapeutic use
chemical_list: D000700:Analgesics; D000069583:Pregabalin; D005680:gamma-Aminobutyric Acid