Worse health-related quality of life, impaired functioning and psychiatric comorbidities are associated with excess mortality in patients with severe chronic pain

Abstract

Background: Severe chronic pain that interferes with daily activities is associated with an increased risk of mortality. We assessed the overall mortality of tertiary chronic pain patients in comparison with the general population, with a special aim to analyse the association of health-related quality of life (HRQoL) and its dimensions with the risk of death.

Methods: In this prospective observational follow-up study, patients with non-cancer chronic pain attended an outpatient multidisciplinary pain management (MPM) episode in a tertiary pain clinic in 2004-2012 and were followed until May 2019. Mortality between the patients and the general population was compared with standardized mortality ratios (SMR) in different age groups. Causes of death and comorbidities were compared among the deceased. Association of mortality and HRQoL and its dimensions, measured with the 15D instrument, was studied with Cox proportional hazards model.

Results: During a mean of 10.4-year follow-up of 1498 patients, 296 died. The SMR in the youngest age group (18-49 years) was significantly higher than that of the general population: 2.6 for males and 2.9 for females. Even elderly females (60-69 years) had elevated mortality (SMR 2.3). Low baseline HRQoL at the time of MPM, as well as poor ratings in the psychosocial dimensions of HRQoL, was associated with an increased risk of death.

Conclusions: Our results support the role of HRQoL measurement by a validated instrument such as the 15D in capturing both the physical and the psychological symptom burden, and consequently, an elevated risk of death, in patients with chronic pain.

Significance: Severe chronic pain is associated with elevated mortality. In patients in chronic pain under 50 years old, the mortality was 2.5-3 times higher than in the general population. Psychological distress appears to contribute to the increased mortality. Regular follow-up by health-related quality of life (HRQoL) measurement could be useful in identifying patients in chronic pain who are in need of intensive symptom management and to prevent early death.

FIGURE 1

The standardized mortality ratios according to the age groups. For the age group 18–49 years, the SMR was 2,9 for females and 2,6 for males. Note the logarithmic scale of the y‐axis. The p for linearity of the SMRs according to the age groups for females and males was 0.049 and 0.007, respectively

FIGURE 2

The association of the symptoms in 15D dimensions and the hazard of death in two groups, <60 years old and >= 60 years old according to the age at baseline. All dimension scores are standardized to z‐scores of the whole study sample for comparability. An increasing dimension score indicates less severe symptoms in the 15D. If the confidence interval of HR is below 1, it indicates that worse symptoms in the dimension are associated with statistically significant increase in the risk of death. HRs are obtained from parallel age‐ and gender‐adjusted Cox proportional hazard models with each individual dimension as a predictor variable. In other words, the models are not adjusted for other dimensions, and the age adjustment is done inside the two age groups. HR, hazard ratio

FIGURE 3

The results of the age‐ and gender‐adjusted restricted cubic Sp‐lines cox proportional hazards model exploring the non‐linear association of the 15D score and the hazard of death. A median of the study population’s 15D score (0.717) was set to have a relative HR of 1. As the 15D score decreases, a marked increase in the hazard of death is observed. An increase in the 15D score is not clearly associated with the reduction in the hazard of death