The only study involving a nationally representative sample to estimate dementia prevalence in Colombia has been the EPINEURO. This was a population-based survey of a stratified random sample of urban and rural residents of five regions of Colombia. The purpose of this paper was to estimate the number of people suffering from dementia and in particular Alzheimer's disease (AD) in Colombia by severity stage. Using secondary data, updated population estimations and a cohort component population projection method we estimated the number of patients with AD by stage in Colombia.The model rests on three basic elements: prevalence, incidence and mortality rates by disease's stage.We estimated three scenarios. The first one is the baseline in which we applied to the population projection prevalence rates by gender, adjusted dementia cases by 70% to get AD cases and distributed patients annually using the following criteria: 48% mild, 31% moderate, and 21% severe. In this baseline model there is no transition between stages. The second and third scenarios modeled transition dynamic between stages. The number of people with AD could be approximately 220 000 in 2015, and 260 000 in 2020. We estimated three scenarios to investigate what could be the distribution of the population with the disease by stage. Depending on the assumptions made regarding the stage at which new cases are identified, the share of those in the moderate stage could be up to 20 percentage points higher than a baseline model with fixed proportions. The current estimates in the published literature could be underestimating the number of people with dementias and AD by 50%. The fastest growth in aging is happening in developing countries with profound implications not only for the older people themselves, but for their households, the social and community infrastructure and for social policy. Developing societies, as Colombia, are now faced with an ageing population and a more generous coverage of healthcare needs. Since the services required by patients are differential according to the stage and disease involvement, research involving stage distribution to estimate burden of the disease and costs are required. Transition dynamic People 60+ years with Alzheimer's Disease in Colombia