There is need for accurate projections of the future dementia burden to prepare healthcare systems and policymakers. Existing projections only account for population ageing, not for observed declines in age-specific dementia incidence of 13% per decade. We developed a dementia microsimulation model that synthesizes population-based data from the Rotterdam Study with changes in demographics between birth cohorts from the early 1900s onwards. We determined dementia prevalence and incidence until 2050 for three different dementia incidence trend scenarios: (1) stable age-specific incidence, (2) linear decline by 13% per decade, (3) nonlinear declines averaging 13% per decade. Assuming a stable age-specific incidence resulted in a 130% increase in incidence and 118% in prevalence between 2020 and 2050. By contrast, the linearly declining trend resulted in substantially smaller increases of 58% in incidence (95%CI: 29–87%), and 43% in prevalence (95%CI: 13–66%), corresponding to 39% lower incidence and 36% lower prevalence by 2050 than in the stable-incidence scenario. Results for various non-linear declines fell between the stable and linear trend. The future burden of dementia is highly susceptible to achievable changes in age-specific incidence. Extension of previously established secular trends globally would reduce widely upheld projections of new dementia cases until 2050 by 39%.

需要准确预测未来的痴呆症负担，以便为医疗保健系统和政策制定者做好准备。现有预测仅考虑人口老龄化，而不是观察到的特定年龄痴呆发病率每十年下降 13%。我们开发了一个痴呆症微观模拟模型，该模型综合了鹿特丹研究中基于人群的数据以及 1900 年代初以来出生队列之间的人口统计变化。我们确定了 2050 年之前三种不同痴呆发病率趋势情景的痴呆患病率和发病率：(1) 稳定的特定年龄发病率，(2) 每十年线性下降 13%，(3) 每十年平均下降 13% 的非线性下降。假设年龄别发病率稳定，2020 年至 2050 年间发病率增加 130%，患病率增加 118%。相比之下，线性下降趋势导致发病率大幅增加 58%（95%CI：29-87%），患病率增加 43%（95%CI：13-66%），对应于发病率降低 39% 和 36%到 2050 年的流行率低于稳定发病率情景中的流行率。各种非线性下降的结果介于稳定和线性趋势之间。痴呆症的未来负担极易受到特定年龄发病率的可实现变化的影响。在全球范围内扩展先前确定的长期趋势将使广泛支持的到 2050 年新痴呆病例的预测减少 39%。各种非线性下降的结果介于稳定和线性趋势之间。痴呆症的未来负担极易受到特定年龄发病率的可实现变化的影响。在全球范围内扩展先前确定的长期趋势将使广泛支持的到 2050 年新痴呆病例的预测减少 39%。各种非线性下降的结果介于稳定和线性趋势之间。痴呆症的未来负担极易受到特定年龄发病率的可实现变化的影响。在全球范围内扩展先前确定的长期趋势将使广泛支持的到 2050 年新痴呆病例的预测减少 39%。