Circannual rhythmicity and long-term continuity of treatment dispensing in cluster headache: a French Nationwide SNDS study (2021–2025)

Cluster headache (CH) displays marked circadian and circannual rhythmicity, but population-level evidence remains limited. Using the exhaustive French National Health Data System (SNDS), we investigated nationwide temporal patterns in the dispensing of acute CH treatments between 2021 and 2025. All individuals receiving at least one reimbursed treatment specifically indicated for CH (subcutaneous sumatriptan or oxygen therapy) were identified to estimate the national treated burden. Seasonal analyses among subcutaneous sumatriptan users assessed treatment intensity (mean boxes dispensed per patient-month) and population-level activity (number of treated patient-months). Longitudinal analyses evaluated annual and quarterly treatment continuity. Between 2021 and 2025, 69,113 individuals received at least one CH-specific reimbursed treatment nationwide, including 39,788 treated with subcutaneous sumatriptan. Treatment intensity peaked in midsummer (11.12 boxes in August and 10.96 in July), whereas population-level treatment activity remained elevated from summer into early autumn (18,836 patient-months in July, 18,021 in September, and 18,277 in October). Significant geographic gradients were observed, with higher dispensing levels in southern regions (12.04 boxes) than in the Paris area (10.25) and northern regions (9.55). Longitudinal analyses revealed marked heterogeneity in treatment continuity. Five-year persistence ranged from 17.9% among patients treated with SC sumatriptan alone to 43.1% among those receiving SC sumatriptan, oxygen therapy, and verapamil, while the proportion of patients experiencing three treatment-free quarters decreased from 60.1% to 12.6% across these treatment groups. This nationwide study demonstrates distinct circannual patterns in treatment intensity and population-level treatment activity, together with marked geographic and longitudinal heterogeneity in real-world practice.