Dementia is a leading cause of death and disability in the United States. The absolute number of adults affected by dementia is expected to rise in response to population aging, although recent studies have reported declines in the age-specific risk of dementia across sequential birth cohorts. The underlying mechanisms driving this decline remain unclear, nor is it clear whether and to what extent these trends will sustain in the future. Understanding these trends in the context of demographic and epidemiological forces would provide valuable information about the current landscape of dementia and its future burden. Microsimulation is a modeling technique that lends itself to this objective as it allows for studying life course dynamics in a counterfactual framework. In addition, it can be used to generate population forecasts in a stochastic rather than deterministic way, overcoming the untenable assumptions on which many extrapolation-based methods rely. This dissertation has three parts. In the first part, I use the parametric g-formula to examine the risk of dementia under hypothetical interventions on its risk factors while accounting for the competing risk of death. I find that observed rises in educational attainment and reduced cardiovascular disease reduce the cumulative risk of dementia but this reduction is offset after accounting for expected increases in diabetes and obesity. The second part develops a probabilistic approach to forecasting dementia incidence, prevalence, and mortality through the year 2050 while accounting for compositional and epidemiological changes in the population. I estimate a more than two-fold increase in the number of adults aged 65 years or over with dementia from 6.3 million in 2010 to 16.3 million in 2050. In the final part, I forecast the economic burden of dementia by combining estimates from part two with linked Medicare claims and self-reported out-of-pocket expenditures. I estimate that the direct, incremental out-of-pocket expenditures and costs to Medicare for dementia may rise from $145.12 billion in 2010 to $378.98 billion by 2050.