Multimorbidity and Sickness Absence/Disability Pension in Patients With Cluster Headache and Matched References: A Swedish Register-Based Study

BACKGROUND AND OBJECTIVES: Multimorbidity among patients with cluster headache (CH) is considered to be high, but large studies are lacking. The aims were to explore the occurrence of diagnosis-specific multimorbidity among patients with CH and matched references and possible associations of this with their sickness absence and disability pension. METHODS: We performed a register-based study of patients with CH and matched references, regarding their multimorbidity, sickness absence, and disability pension. Data were obtained from 2 nationwide registers: Statistics Sweden's Longitudinal Integration Database for Health Insurance and Labor Market Studies (LISA) (for sociodemographics in 2009, sickness absence, and disability pension in 2010) and The National Board of Health and Welfare's specialized outpatient and inpatient registers for diagnosis-specific health care in 2001–2010 (for identifying patients with CH and multimorbidity, defined by ICD-10 codes). The prevalence and number of net days of sickness absence and/or disability pension in 2010 were calculated, in general and by multimorbidity. Odds ratios (OR) with 95% confidence intervals (CIs) were calculated for comparison of each diagnostic group with references without the chosen morbidity. RESULTS: We analyzed 3,240 patients with CH, aged 16–64 years, and living in Sweden in 2010 and 16,200 matched references. A higher proportion of patients with CH had multimorbidity (91.9%) than of references (77.6%), OR 3.263 (95% CI 2.861–3.721), both in general and regarding all analyzed diagnostic groups. Differences were particularly high for diagnoses relating to the nervous (CH 51.8% vs references 15.4%), OR 5.922 (95% CI 5.461–6.422), and musculoskeletal (CH 39.0% vs references 23.7%), OR 2.057 (95% CI 1.900–2.227), systems. Multimorbidity rates were overall higher among women in patients with CH (96.4% vs men 89.6%). Patients with CH had a higher mean number of days of sickness absence and disability pension compared with references, 63.15 vs 34.08 days. Moreover, multimorbidity was associated with a higher mean number of such days in patients with CH, 67.25, as compared with references, 40.69 days. DISCUSSION: The proportions of multimorbidity were high in both patients with CH and references, however, higher in the patients with CH, who also had higher sickness absence and disability pension levels. In particular, CH patients with multimorbidity and of female sex had high sickness absence and disability pension levels.