Aim The aim of the present study was to evaluate the age‐specific prevalence of dementia, and develop a metabolic risk indicator for dementia according to sex. Methods This cross‐sectional study was carried out from September 2007 through December 2012 with 19 935 elderly participants in metropolitan Seoul, Korea. Multiphase assessments were used to measure metabolic risk factors and confirm dementia according to sex. Specifically, multivariate logistic regression analyses were used to identify how elderly men and women differed in regard to metabolic risk indicators of dementia. Results The adjusted prevalence rates of dementia in elderly Seoul residents were estimated at 4.9%, 6.1% and 5.6% in men, women and the overall population, respectively. Stroke conferred an odds ratio of 5.14 (95% CI 3.91–6.77) and 2.55 (95% CI 2.01–3.25) in men and women, respectively. Additionally, within the female population, diabetes mellitus conferred an odds ratio of 1.29 (95% CI 1.09–1.53), whereas alcohol consumption conferred an odds ratio of 0.77 (95% CI 0.61–0.97). Conclusions Stroke played a primary role as a metabolic risk indicator of dementia in elderly men, while diabetes mellitus and alcohol abstinence were important metabolic risk factors in elderly women. Taken together, the data show that when designing preventative measures against dementia based on metabolic risk, sex needs to be taken into account. Geriatr Gerontol Int 2017; ••: ••–••.