Tracing temporal trends in dementia incidence over 25 years in central Stockholm, Sweden.

INTRODUCTION: Recent reports from high-income countries have suggested a declining incidence of dementia. METHODS: Trends in dementia incidence over 25 years among people >/=75 years of age were examined using two population-based cohort studies: the Kungsholmen Project (KP, n = 1473, 1987-1998) and the Swedish National study on Aging and Care in Kungsholmen (SNAC-K, n = 1746, 2001-2013). RESULTS: We identified 440 (29.9%) and 388 (22.2%) incident dementia cases in the KP and SNAC-K cohorts, respectively. The incidence of dementia declined by 30% (hazard ratio [HR] = 0.70; 95% confidence interval [CI] 0.61-0.80) during the second decade. Adjustment of education, psychosocial working conditions, lifestyle, and vascular diseases did not substantially change the results (HR = 0.77, 95% CI 0.65-0.90). This decline was observed particularly in women and people with elementary education. DISCUSSION: Our study provides direct evidence of a declining trend in dementia incidence. Improved cognitive reserve and cardiovascular health could partially explain the decline.