Somatic Comorbidity in patients with chronic widespread pain in an outpatient secondary care center for rheumatology and rehabilitation in The Netherlands

Background: Comorbidity, defined as one or more additional disease(s) among patients with an index-disease, can affect the treatment and the prognosis of the index disease.1,2 Although numerous studies address the prevalence of somatic complaints in patients with chronic widespread pain (CWP), the prevalence of somatic comorbidity has not been studied in detail in these patients and, more specifically, this prevalence has not been compared to the prevalence in the general population.2 Objectives: First aim was to describe the prevalence of somatic comorbidity in patients with CWP. Second aim was to compare this prevalence with the prevalence rates in the general Dutch population and to describe the risk factor of these comorbidities for patients with CWP. Methods: A cohort study on somatic comorbidity was conducted among 1238 patients with CWP referred to an outpatient secondary care center for rheumatology and rehabilitation in the Netherlands. Data on comorbidity were collected by means of a questionnaire including 15 chronic somatic conditions, adapted from the Health Interview Survey of the Statistics Netherlands.3 Statistical analyses included descriptive statistics, Chi-square tests and Standardized Mortality Ratios (SMR). SMR quantifies the disease risk of a study population compared to the general population. Results: 84% of the subjects reported one or more somatic comorbidities. The most frequently reported comorbidities were migraine (52%), dizziness with falling (24%), hypertension (23%), incontinence (19%) and chronic pulmonary disease (15%). In comparison with the Dutch population, 13 of the 15 somatic comorbidities were significantly (P