Keele Research Repository

Background
Moderate to severe chronic pain affects one in five of adults. The prevalence and impact of pain increase with age. Pain may increase the risk of mortality but the relationship is not clear.

Aims
To test the hypothesis that pain increases the risk of mortality, to test if the relationship was dependent on pain classification and identify mediators and moderators of the relationship.

Methods
A systematic review and meta-analysis evaluated existing evidence. Survival analyses (Cox’s proportional hazard modelling and a novel technique to assess mediation within survival models) were conducted on two large population studies of adults aged ≥50 years; the English Longitudinal Study of Ageing (ELSA) (n=6324) and the North Staffordshire Osteoarthritis Project (NorStOP) (n=10985). Lifestyle, health, social and psychological factors were tested as potential mediators. Sex and comorbidity were tested as moderators.

Results
In the systematic review pooled analysis from 7 studies revealed a modest but non-significant risk of mortality for people with chronic pain (Mortality Rate Ratio 1.14, 95%CI (0.95, 1.37)). In survival analyses the relationship with mortality was influenced by pain classification: pain that was troubling (1.29 (1.12, 1.49)) or that interfered with daily activities (1.88 (1.54, 2.29)) was associated with an increased risk of mortality while reporting any pain was not (1.06 (0.95, 1.19)).
The strongest mediators in ELSA that were replicated in NorStOP were functional limitation (Hazard Ratio 1.31; 95%CI (1.20, 1.39)), physical inactivity (1.14 (1.10, 1.20)) and poor self-rated health (1.32 (1.23, 1.41)). Sex and comorbidity moderated the extent of some mediating pathways (e.g. depression) but the findings were inconsistent between datasets.

Conclusion
Specific opportunities to reduce mortality risk for people with pain were identified. At a population level, mortality risk for people with pain could be reduced by the effective management of pain and its impact.