The association between migraine and dementia - a national register-based matched cohort study.

Objectives: Migraine and dementia, two major public health challenges, are associated, but more knowledge is needed to understand their relationship. Objectives of this study were to investigate 1) the association between non-self-reported measures of migraine and dementia, and whether dementia was associated with 2) migraine without aura (MO) and with aura (MA) in combination with migraine medication use, and 3) migraine severity operationalized as the number of migraine prescriptions.

Study Design: Matched cohort study.

Methods: National register data were obtained from individuals born between 1934 and 1958. Migraine cases (aged 25-58 years) were identified by migraine diagnoses and redeemed migraine medication. Migraine cases were matched with non-cases (N = 340,850) and date of diagnosis or medication redemption was defined as index year. Dementia was identified by dementia diagnoses and redeemed dementia medication.

Results: We observed a 1.46 (95% CI: 1.26-1.69) times higher dementia rate in individuals with a migraine diagnosis and a 0.86 (95% CI: 0.76-0.97) times lower rate when using migraine medication. We found the highest dementia rate among individuals with MA, who also used migraine medication (HR = 2.23; 95% CI: 1.19-4.17), and the lowest rate among individuals with MO, who also used medication (HR = 1.25; 95% CI: 0.75-2.10). The number of migraine medication prescriptions was not associated with dementia.

Conclusions: Being registered with a migraine diagnosis was associated with a higher dementia rate, while use of prescribed migraine medication was not. The differences in the dementia rate among migraine cases identified via diagnoses versus medications warrants further investigation.