title: Chronic pain and mortality: a systematic review.
abstract: BACKGROUND
  Chronic pain is common, often widespread and has a substantial impact on health and quality of life. The relationship between chronic pain and mortality is unclear. This systematic review aimed to identify and evaluate evidence for a relationship between chronic pain and mortality.
  
  
  METHODS
  A search of ten electronic databases including EMBASE and MEDLINE was conducted in March 2012, and updated until March 2014. Observational studies investigating the association between chronic or widespread pain (including fibromyalgia) and mortality were included. Risk of bias was assessed and a meta-analysis was undertaken to quantify heterogeneity and pool results. A narrative review was undertaken to explore similarities and differences between the included studies.
  
  
  RESULTS
  Ten studies were included in the review. Three reported significant associations between chronic or widespread pain and mortality in unadjusted results. In adjusted analyses, four studies reported a significant association. The remaining studies reported no statistically significant association. A meta-analysis showed statistically significant heterogeneity of results from studies using comparable outcome measures (n = 7)(I2 = 78.8%) and a modest but non-significant pooled estimate (MRR1.14,95%CI 0.95-1.37) for the relationship between chronic pain and all-cause mortality. This association was stronger when analysis was restricted to studies of widespread pain (n = 5,I2 = 82.3%) MRR1.22(95%CI 0.93-1.60). The same pattern was observed with deaths from cancer and cardiovascular diseases. Heterogeneity is likely to be due to differences in study populations, follow-up time, pain phenotype, methods of analysis and use of confounding factors.
  
  
  CONCLUSIONS
  This review showed a mildly increased risk of death in people with chronic pain, particularly from cancer. However, the small number of studies and methodological differences prevented clear conclusions from being drawn. Consistently applied definitions of chronic pain and further investigation of the role of health, lifestyle, social and psychological factors in future studies will improve understanding of the relationship between chronic pain and mortality.
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Staffordshire, United Kingdom.
authors.forename: Diane
authors.initials: D
authors.lastname: Smith
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Staffordshire, United Kingdom.
authors.forename: Ross
authors.initials: R
authors.lastname: Wilkie
authors.affiliation: Warwick Centre for Applied Health Research and Delivery (WCAHRD), Division of Health Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom.
authors.forename: Olalekan
authors.initials: O
authors.lastname: Uthman
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Staffordshire, United Kingdom.
authors.forename: Joanne L
authors.initials: JL
authors.lastname: Jordan
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Staffordshire, United Kingdom.
authors.forename: John
authors.initials: J
authors.lastname: McBeth
mesh_terms: D000367:Age Factors; D002318:Cardiovascular Diseases / Q000401:mortality / Q000473:pathology; D059350:Chronic Pain / Q000401:mortality / Q000473:pathology*; D016208:Databases, Factual; D006801:Humans; D008171:Lung Diseases / Q000401:mortality / Q000473:pathology; D009369:Neoplasms / Q000401:mortality / Q000473:pathology; D012737:Sex Factors