Is chronic pain associated with subsequent cancer? A cohort record linkage study.

A previous study has reported that chronic pain is associated with a higher incidence of overall and site-specific cancer in subsequent years. The aim of this study was to confirm or refute these findings. In 1996, a cohort of 6940 individuals was recruited, and information on chronic pain, general health and socio-demographic details collected. Ten years later, a record linkage study was conducted between these data and the routinely collected national dataset for cancer registration. Hazard ratios for the incidence of all cancers and eight cancer-specific sites by chronic pain status were calculated. Eighty-four percent of individuals from the original cohort were linked. After excluding those with a known previous cancer diagnosis, all non-melanoma skin cancers and cancers which were not first occurrences, a total of 646 cancers had occurred in 607 people since the baseline study. The overall cancer incidence in the cohort was 10.4% over the 10 years. There were no significant associations between chronic pain and all cancer, or any of the eight cancer-specific sites, after adjustment for age and sex. There was a significant increased risk of developing lymphoma/leukaemia amongst those with all chronic pain and various causes of chronic pain on univariate analysis. After adjustment, these trends remained, although most of the associations were no longer significant. There were no significant differences between those with severe chronic pain compared to those with mild chronic pain. The findings suggest that those with chronic pain are not at a significantly increased risk of developing cancer.