The relationship between medical comorbidity and self-rated pain, mood disturbance, and function in older people with chronic pain

Background. Aging is associated with greater risk for many illnesses and the prospect of multiple, concurrent disease states. Chronic pain is also very common in advanced age, and there is likely to be a relationship with comorbid burden, but few studies have examined this issue. This study tests the hypothesis that comorbid burden is associated with greater levels of self-reported pain and associated disturbance in mood and function. Methods. Psychometric and medical data were collected from 562 patients (mean age=76.3 years) attending a geriatric pain clinic. The number of categories endorsed on the Cumulative Illness Rating Scale (CIRS) score was used to measure accumulated comorbid burden. These groups were tested for differences in the severity of self-reported pain. The predictive capacity of comorbid burden for explaining variance in mood disturbance and functional disability was assessed after controlling for any differences in age and severity of pain. Results. Over 50% of the sample had three or more comorbid problems. Groups with greater levels of comorbidity scored higher on the Present Pain Intensity Index, the sensory and affective subscales of the McGill Pain Questionnaire. Multiple regression analysis showed that the CIRS score explained a significant proportion of the variance in scores on the Geriatric Depression Scale (4.1%), Human Activities Profile (4.8%), and the physical domain of the Sickness Impact Profile (5.9%). Conclusion. Greater levels of comorbidity are associated with reports of more severe pain, more depressive symptoms, reduced activity levels, and higher physical impact from pain.