Rationale and Background
Cluster headache (CH) is a primary headache disorder characterized by episodes of severe, strictly unilateral pain accompanied by ipsilateral conjunctival injection, lacrimation, nasal congestion, rhinorrhoea, forehead and facial sweating, miosis, ptosis and/or eyelid oedema, and/or with restlessness or agitation, that lasts 15- 180 minutes and occurs from once every other day to eight times a day. CH affects 0.1% of the population and its clinical management is broadly divided into acute treatment and prophylactic treatments.
The EHDEN (European Health Data & Evidence Network) Foundation Research Programmes aim to foster non-competitive research collaborations with Data Partners, Academia, and Industry across various therapeutic areas. To obtain a better understanding of the characteristics of patients with CH as well as other headache disorders in a real-world setting, a pilot study within the Neuroscience Research Program of the EHDEN Foundation will be conducted. The pilot comprises a database feasibility assessment for selection of data partners, protocol development, and final analysis.
Research question and Objectives
The aim of this study is to obtain a better understanding of the characteristics of patients with cluster headache (CH) as well as other headache disorders in a real-world clinical setting. The primary objective of the study is to describe the sex and age of patients in each of the cohorts derived from the study population (see Population below).
The secondary objectives of this study are:
• To assess patterns of pharmacological treatment, procedures, and emergency room (ER) visits among CH patients and differences from the other cohorts.
• To describe common morbidities among CH patients and differences from the other cohorts as well as the risk of new morbidities after initiating the most frequent treatments.
• Understanding major subgroups of patients by morbidity and treatment.
Research Methods
Study design
The study design comprises a multinational, retrospective cohort study on patients with CH and other headache disorders using routinely collected health data. Data are sourced from selected EHDEN data partners, chosen based on database and cohort feasibility assessments.
Population
The study cohorts will comprise all individuals in the selected EHDEN data partners’ databases during the study period from 2015 to 2024 or latest data coverage with at least 730 days of data (365 days prior to index date and 365 days after index date).
• The CH cohort will comprise all individuals of the study population with a first CH diagnosis, and an observation period starting at least 365 days before and ending the at earliest 365 days after the first CH diagnosis recorded in the database.
• The episodic CH cohort will comprise all individuals of the study population with a first episodic CH diagnosis, and an observation period starting at least 365 days before and ending the at earliest 365 days after the first CH diagnosis recorded in the database.
• The chronic CH cohort will comprise all individuals of the study population with a first chronic CH diagnosis, and an observation period starting at least 365 days before and ending the at earliest 365 days after the first CH diagnosis recorded in the database.
• The PTH cohort will comprise all individuals of the study population with a first PTH diagnosis, and an observation period starting at least 365 days before and ending the at earliest 365 days after the first PTH diagnosis recorded in the database.
• The concussion cohort will comprise all individuals of the study population with a first concussion diagnosis, and an observation period starting at least 365 days before and ending the at earliest 365 days after the first concussion diagnosis recorded in the database.
• The migraine cohort will comprise all individuals of the study population with a migraine diagnosis, and an observation period starting at least 365 days before and ending the at earliest 365 days after the first migraine diagnosis recorded in the database.
• The chronic migraine cohort will comprise all individuals of the study population with a migraine diagnosis, and an observation period starting at least 365 days before and ending the at earliest 365 days after the first chronic migraine diagnosis recorded in the database.
• The headache cohort will comprise all individuals of the study population with any kind of headache diagnosis, and an observation period starting at least 365 days before and ending the at earliest 365 days after the first headache diagnosis recorded in the database.
• The random sample cohort will be a sample of all individuals with at least one visit and 365 days of observation before that visit and 365 days after.
Variables
The following variables are planned to be collected from the databases to meet the study objectives, depending on availability:
• Sociodemographic characteristics (age, sex, and country).
• Comorbidities
• Treatment and medical interventions.
Data sources
This study will be conducted using routinely collected data from primary care and/or secondary care as available in the EHDEN data partners’ Information System for Research in Primary Care (Sistema d’Informació per al Desenvolupament de la Investigació en Atenció Primària [SIDIAP]) and Integrated Primary Care Information (IPCI) databases. SIDIAP is a database comprising primary care records of more than 8 million individuals in the Catalonia region in Spain since 2006, with 5.8 million active individuals in June 2021 (75% of the population in the region). IPCI is a database containing routinely collected electronic health records (EHR) of approximately 2.5 million patients registered with a selected group of GPs in the Netherlands.
Sample size
No sample size has been calculated.
Data analyses
The data analysis methods aim to characterize and compare the defined cohorts in a summarized manner, using descriptive statistics, statistical comparisons and descriptive clustering methods.