Cause-specific mortality of patients with severe chronic pain referred to a multidisciplinary pain clinic: a cohort register-linkage study

Abstract

<jats:title>Abstract</jats:title> <jats:sec id="j_sjpain-2018-0094_s_999"> <jats:title id="d2482991e26662">Background and aims</jats:title> <jats:p>Almost 20% of the adult population suffers from chronic pain. Chronic pain may be linked to an elevated mortality; however, results from previous studies are inconsistent. Some studies find similar mortality levels in chronic pain patients and pain-free controls while other studies show elevated mortality levels among chronic pain patients, primarily with respect to cancer, diseases of the circulatory and respiratory systems, and suicide. These conflicting results are potentially due to different population samples and different operational definitions of chronic pain. Further research on overall and cause-specific mortality in patients with severe chronic pain is needed to inform clinical practice. The objective of this register-linkage study was to investigate whether patients with severe chronic pain referred to multidisciplinary pain treatment have higher cause-specific mortality rates than the general population.</jats:p></jats:sec> <jats:sec id="j_sjpain-2018-0094_s_998"> <jats:title id="d2482991e26670">Methods</jats:title> <jats:p>In this register-linkage cohort study, data from 6,142 chronic pain patients (female: <jats:italic>n</jats:italic>=3,941, male: <jats:italic>n</jats:italic>=2,201, mean age: 48.2±14.2; range: 16–97 years) attending an interdisciplinary Pain Center in Odense, Denmark from 2005 to 2014 were linked to the Danish Register of Causes of Death. Age and gender standardized mortality ratios (SMRs) with their 95% confidence intervals (CI) were calculated and compared with those of the general population. Data from the general population was extracted from the Danish Register of Causes of Death, and Causes of death were classified according to national Classification of Disease (ICD-10).</jats:p></jats:sec> <jats:sec id="j_sjpain-2018-0094_s_997"> <jats:title id="d2482991e26684">Results</jats:title> <jats:p>In all, 276 deaths (women: <jats:italic>n</jats:italic>=152, men: <jats:italic>n</jats:italic>=124) were observed among the chronic pain patients, and a six-fold higher overall mortality rate was found [SMR: 6.2 (95% CI: 5.5–7.0)] compared with the general population. Elevated cause-specific mortality rates were noted for chronic patients with respect to cancer and neoplasms [4.7 (95% CI: 3.7–5.9)], diseases of the circulatory system [5.7 (95% CI: 4.3–7.3)], diseases of the respiratory system [8.7 (95% CI: 6.2–11.9)], and suicide [7.3 (95% CI: 2.7–15.9)].</jats:p></jats:sec> <jats:sec id="j_sjpain-2018-0094_s_996"> <jats:title id="d2482991e26698">Conclusions</jats:title> <jats:p>The overall mortality rate of patients with severe chronic pain in this study was six-fold higher than the rate of the general population in this region. This was reflected in select specific causes of death (cancer and neoplasms, diseases of the circulatory system, diseases of the respiratory system, and suicide). The results are in agreement with previous studies and emphasize the need to understand which factors causally affect this increased mortality allowing for targeted interventions in similar chronic pain populations.</jats:p></jats:sec> <jats:sec id="j_sjpain-2018-0094_s_995"> <jats:title id="d2482991e26707">Implications</jats:title> <jats:p>Potential reasons for the excess mortality should be adequately addressed by future studies in order to better target this in the management of these patients. The chronic pain population included in this study may have several comorbidities contributing to the increased mortality. To better address these aspects, complete medical profiles are needed in future studies. In addition, implementation of management strategies towards potential risk factors such as poor diet, low levels of physical activity, smoking, and high BMI as well as sleep deprivation and morphine use previously shown associated with having pain may reduce the excess mortality ratio.</jats:p></jats:sec>

Lifestyle and Chronic Pain across the Lifespan: An Inconvenient Truth?

“…Similar to sleep, diet—and often related overweight/obesity—represents another overlooked lifestyle factor of importance to chronic pain. Poor dietary habits is one of those adverse lifestyle factors that partly accounts for the observed excess mortality among people having chronic pain, leading to the suggestion to target dietary habits in chronic pain management …”

“…Chronic pain is associated with decreased life expectancy, in part because of excess deaths from cancer and cardiovascular disease . This association is mainly explained by adverse lifestyle factors such as low levels of physical activity, poor dietary habits, and smoking …”

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

“…A high burden of chronic pain may manifest in, for example, difficulties in maintaining a healthy lifestyle or delays in seeking medical treatment for disease symptoms. Cardiovascular‐ and cancer‐related mortality is elevated in the chronic pain population (Fayaz et al, 2016; Macfarlane et al, 2017; Torrance et al, 2010; Vaegter et al, 2019). Poor diet, overweight, low levels of physical activity and smoking have consistently been concluded to mediate the relationship between chronic pain and excess mortality (Andersson, 2009; Macfarlane et al, 2017; Owen‐Smith et al, 2019; Smith, Wilkie, Croft, Parmar, et al, 2018).…”

“…Chronic pain is associated with poor self‐rated health and low health‐related quality of life (HRQoL) (Breivik et al, 2006; Eriksen et al, 2003; Vartiainen et al, 2016). Evidence consistently shows that mortality is higher in patients with severe chronic pain than in the general population (Macfarlane et al, 2017; Smith et al, 2014; Vaegter et al, 2019). The experience of chronic pain per se is not associated with excess mortality (Andorsen et al, 2016; Åsberg et al, 2016; Macfarlane et al, 2007), but an increased risk of death is seen when chronic pain is either severe (Torrance et al, 2010) or interferes with daily life and physical functioning (Macfarlane et al, 2017; Smith, Wilkie, Croft, Parmar, et al, 2018).…”

“…Adverse lifestyle factors, such as overweight, poor diet, smoking, physical inactivity, sleep disturbances and substance abuse disorders have been identified as possible mediators between pain and mortality (Andersson, 2009; Macfarlane et al, 2017; Owen‐Smith et al, 2019; Smith, Wilkie, Croft, Parmar, et al, 2018). In support of the relevance of lifestyle factors, cardiovascular risk factors and metabolic syndrome are highly prevalent in patients with chronic pain (Goodson et al, 2013), and chronic pain patients’ excess mortality from cardiovascular diseases has emerged in several studies worldwide (Fayaz et al, 2016; Macfarlane et al, 2017; Torrance et al, 2010; Vaegter et al, 2019). Even cancer mortality, less obviously explained by lifestyle factors, is higher in chronic pain patients than in the general population (Torrance et al, 2010; Vaegter et al, 2019).…”