To describe headache and pain multimorbidity in a national cohort of U.S. Veterans with cluster headache (CH) diagnosis.

CH is the most common autonomic cephalalgia. Persons with CH, even during the interictal headache free period, demonstrate increased cutaneous pain sensitivity. We hypothesize that persons with CH have a high degree of headache and pain multimorbidity.    

Data are from the national Veterans Health Administration (VHA) headache cohort (FY2008-FY2019), an administrative dataset containing all Veterans in the VHA with an associated ICD9 or ICD10 headache diagnosis. Specific cluster headache ICD diagnostic codes include: ICD9 (339.0/339.00/339.01/339.02) and ICD10 (G44.001/G44.009/G44.011/G44.019/G44.021/G44.029). Data included sociodemographic factors, headache multimorbidity, concurrent medical, pain, psychiatric, and sleep disorder comorbidities (occurring 12 months before and up to 6 months after headache diagnosis), pharmacy, prosthetics and provider type associated with headache diagnosis. SAS 9.4 was used for statistical analyses.

Within the national VHA population between fiscal years 2008 and 2019, a total of 24,140 Veterans (21,772 men, 2,368 women) had a clinical encounter where a CH diagnosis was given. Veterans were middle aged (50.6±14.6 years) with men significantly older than women (51.5±14.6 vs 42.2±12.0; p<0.001) and predominantly Caucasian (63.9% white, 22.5% black, 6.6% Hispanic). 68% of Veterans with CH had another headache diagnosis with headache not otherwise specified (56.7%) and migraine being most common (38.6%), the latter being significantly more frequent in women than men (61.8% vs. 36.0%; p<0.001). The majority of Veterans with CH, 87.6%, had a concurrent non-headache pain diagnosis with limb pain (74.8%) and back pain (60.0%) being most common. Among Veterans with CH, 35.2% had PTSD, 37.7% had depression (55.4% women, 35.7% men; p<0.001), 69.8% had a current or past drug use disorder, and 28.9% had sleep apnea.

Headache and pain multimorbidity is common among Veterans with CH and sex is a factor affecting which comorbidities occur.