Severe chronic pain is associated with increased 10 year mortality. A cohort record linkage study

Abstract

Previous research has clearly demonstrated a link between chronic pain and poor health, and has suggested a link with increased mortality, though the latter is less consistent. In 1996 a cohort of 6940 individuals was recruited, and information collected, about reported chronic pain status, general health and socio-demographic details. Ten years later, a record linkage was conducted between these data and the routinely collected national dataset for death registration. Primary cause of death was classified according to ICD-10 codes. Survival analysis was conducted to obtain unadjusted and multi-adjusted hazard ratios (HR) for all-cause, system-specific and disease-specific mortality by chronic pain status. A total of 5858 (84.4%) of individuals from the original cohort were linked, including 1557 (26.6%) who had died. Survival analysis found significant associations between any reported chronic pain and all-cause mortality (HR 1.32, 99% CI, 1.14-1.54) and a number of specific causes. However, when we adjusted for socio-demographic factors and reported long-term limiting illness, the significant association was lost. Survival among those reporting severe chronic pain was significantly worse than among those reporting mild or no chronic pain. After adjustment for socio-demographic factors and reported long-term limiting illness, severe chronic pain remained significantly associated with all-cause mortality (HR 1.49, 99% CI 1.21-1.84) and all circulatory system disease deaths (HR 1.68, 99% CI 1.20-2.35). The evident association between any chronic pain and increased mortality can apparently be explained by confounding caused by socio-demographic factors. However, severe chronic pain is associated with increased risk of mortality, independent of socio-demographic factors.