Data Source and Study Design

This cohort study utilized the data from the Longitudinal Health Insurance Database (LHID), one of the data subsets of the National Health Insurance Research Database (NHIRD). The NHIRD was established by the National Institutes of Health (NHRI) and has recorded the health information of 99% of the residents in Taiwan. The LHID contained the medical records of one million beneficiaries randomly selected from the National Health Insurance program. The definition of the disease in the LHID was according to the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). The index date was defined as the date of receiving Fz therapy. Each migraine patient (ICD-9-CM 346) who received Fz treatment for more than one month was matched to a subject without Fz treatment by age, sex, index year, and the interval between the onset of migraine and the first Fz consultation. People aged < 20 years or > 90 years were excluded. Moreover, subjects with Parkinson’s disease (PD, ICD-9-CM 332), parkinsonism (ICD-9-CM 333), stroke (ICD-9-CM 430-438), dementia (ICD-9-CM 290, 294.1, and 331.0), head injury (ICD-9-CM 850-854, 959.01), or hydrocephalus (ICD-9 331.3-331.5) and those who used anti-psychotics drugs during the study period were also excluded ( Figure 1 ).

Shows the selection process of the participants in the two study cohorts.