||BACKGROUND: Headache has not been established as a risk factor for dementia. The aim of this study was to determine whether any headache was associated with subsequent development of vascular dementia (VaD), Alzheimer's disease (AD) or other types of dementia. METHODS: This prospective population-based cohort study used baseline data from the Nord-Trondelag Health Study (HUNT 2) performed during 1995-1997 and, from the same Norwegian county, a register of cases diagnosed with dementia during 1997-2010. Participants aged >/=20 years who responded to headache questions in HUNT 2 were categorized (headache free; with any headache; with migraine; with non-migrainous headache). Hazard ratios (HRs) for later inclusion in the dementia register were estimated using Cox regression analysis. RESULTS: Of 51,383 participants providing headache data in HUNT 2, 378 appeared in the dementia register during the follow-up period. Compared to those who were headache free, participants with any headache had increased risk of VaD ( N = 63) (multivariate-adjusted HR = 2.3, 95% CI 1.4-3.8, P = 0.002) and of mixed dementia (VaD and AD ( N = 52)) (adjusted HR = 2.0, 95% CI 1.1-3.5, P = 0.018). There was no association between any headache and later development of AD ( N = 180). CONCLUSION: In this prospective population-based cohort study, any headache was a risk factor for development of VaD.