The article presents an updated global cost estimate of dementia for 2015, comparing it to the 2010 estimates. The worldwide costs of dementia were estimated at US $818 billion in 2015, a 35% increase from 2010. The majority of these costs (86%) occur in high-income countries (HICs). Costs are divided into three categories: direct medical costs, direct social care costs, and informal care costs. The study found that the costs of informal care and direct social care remain similar proportions of total costs, while medical sector costs are much lower. The threshold of US $1 trillion is expected to be crossed by 2018. The distribution of costs remains inequitably distributed, with a significant imbalance between the global prevalence of dementia (58% in lower middle-income countries [LMICs]) and the costs (87% in HICs). Sensitivity analyses suggest that assumptions about informal care costs significantly impact the total costs. The study also forecasts that the global costs will continue to grow, reaching around US $2 trillion by 2030.The article presents an updated global cost estimate of dementia for 2015, comparing it to the 2010 estimates. The worldwide costs of dementia were estimated at US $818 billion in 2015, a 35% increase from 2010. The majority of these costs (86%) occur in high-income countries (HICs). Costs are divided into three categories: direct medical costs, direct social care costs, and informal care costs. The study found that the costs of informal care and direct social care remain similar proportions of total costs, while medical sector costs are much lower. The threshold of US $1 trillion is expected to be crossed by 2018. The distribution of costs remains inequitably distributed, with a significant imbalance between the global prevalence of dementia (58% in lower middle-income countries [LMICs]) and the costs (87% in HICs). Sensitivity analyses suggest that assumptions about informal care costs significantly impact the total costs. The study also forecasts that the global costs will continue to grow, reaching around US $2 trillion by 2030.