Is headache a risk factor for dementia? A systematic review and meta-analysis.

OBJECTIVE: In this systematic review and meta-analysis, we critically evaluate available evidence regarding the association between primary headaches and subsequent decline of cognitive function and dementia. BACKGROUND: Recent studies suggested that headache disorders may increase the risk for dementia. However, available studies are conflicting. METHODS: To identify qualifying studies, we searched scientific databases, including Pubmed, Scopus, Web of Science, Science Direct and BMC, screening for relevant papers. In order to reduce the heterogeneity between different studies, the analyses were further subdivided according to the clinical diagnoses and the study methodologies. RESULTS: We identified 23 studies investigating the association between primary headaches and the risk of dementia. Of these, 18 met our inclusion criteria for meta-analysis (covering 924.140 individuals). Overall effect-size shows that primary headaches were associated with a small increase in dementia risk (OR = 1,15; CI 95%: 1,03-1,28; p = 0,02). Analyzing subgroups, we found that migraine was associated with both a moderate increased risk of all-cause dementia (OR = 1,26; p = 0,00; 95% CI: 1,13-1,40) as well as a moderate increased risk of Alzheimer's disease (OR = 2,00; p = 0,00; 95% CI: 1,46-2,75). This association was significant in both case-control and retrospective cohort studies but not in prospective studies. CONCLUSIONS: Our study supports the presence of a link between primary headaches and dementia. However, in the subgroup analysis, only patients with migraine showed a moderate increase risk for all-cause dementia and for Alzheimer's disease. Additional rigorous studies are needed to elucidate the possible role of primary headaches on the risk of developing cognitive impairment and dementia.