IMPORTANCEThe aging of the US population is expected to lead to a large increase in the number of adults with dementia, but some recent studies in the United States and other high-income countries suggest that the age-specific risk of dementia may have declined over the past 25 years. Clarifying current and future population trends in dementia prevalence and risk has important implications for patients, families, and government programs. OBJECTIVE To compare the prevalence of dementia in the United States in 2000 and 2012. DESIGN, SETTING, AND PARTICIPANTS We used data from the Health and Retirement Study (HRS), a nationally representative, population-based longitudinal survey of individuals in the United States 65 years or older from the 2000 (n = 10 546) and 2012 (n = 10 511) waves of the HRS.MAIN OUTCOMES AND MEASURES Dementia was identified in each year using HRS cognitive measures and validated methods for classifying self-respondents, as well as those represented by a proxy. Logistic regression was used to identify socioeconomic and health variables associated with change in dementia prevalence between 2000 and 2012. RESULTSThe study cohorts had an average age of 75.0 years (95% CI, 74.8-75.2 years) in 2000 and 74.8 years (95% CI, 74.5-75.1 years) in 2012 (P= .24); 58.4% (95% CI, 57.3%-59.4%) of the 2000 cohort was female compared with 56.3% (95% CI, 55.5%-57.0%) of the 2012 cohort (P< .001). Dementia prevalence among those 65 years or older decreased from 11.6% (95% CI, 10.7%-12.7%) in 2000 to 8.8% (95% CI, 8.2%-9.4%) (8.6% with ageand sex-standardization) in 2012 (P < .001). More years of education was associated with a lower risk for dementia, and average years of education increased significantly (from 11.8 years [95% CI,9 years] to 12.7 years [95% CI, 12.6-12.9 years]; P < .001) between 2000 and 2012. The decline in dementia prevalence occurred even though there was a significant age-and sex-adjusted increase between years in the cardiovascular risk profile (eg, prevalence of hypertension, diabetes, and obesity) among older US adults. CONCLUSIONS AND RELEVANCEThe prevalence of dementia in the United States declined significantly between 2000 and 2012. An increase in educational attainment was associated with some of the decline in dementia prevalence, but the full set of social, behavioral, and medical factors contributing to the decline is still uncertain. Continued monitoring of trends in dementia incidence and prevalence will be important for better gauging the full future societal impact of dementia as the number of older adults increases in the decades ahead.

IMPORTANCE Cognitive decline is a major cause of disability in stroke survivors. The magnitude of survivors' cognitive changes after stroke is uncertain.OBJECTIVE To measure changes in cognitive function among survivors of incident stroke, controlling for their prestroke cognitive trajectories. DESIGN, SETTING, AND PARTICIPANTS Prospective study of 23 572 participants 45 years or older without baseline cognitive impairment from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) cohort, residing in the continental United States, enrolled 2003-2007 and followed up through March 31, 2013. Over a median follow-up of 6.1 years (interquartile range, 5.0-7.1 years), 515 participants survived expert-adjudicated incident stroke and 23 057 remained stroke free. EXPOSURE Time-dependent incident stroke. MAIN OUTCOMES AND MEASURES The primary outcome was change in global cognition (Six-Item Screener [SIS], range, 0-6). Secondary outcomes were change in new learning (Consortium to Establish a Registry for Alzheimer Disease Word-List Learning; range, 0-30), verbal memory (Word-List Delayed Recall; range, 0-10), and executive function (Animal Fluency Test; range, Ն0), and cognitive impairment (SIS score <5 [impaired] vs Ն5 [unimpaired]). For all tests, higher scores indicate better performance. RESULTS Stroke was associated with acute decline in global cognition (0.10 points [95% CI, 0.04 to 0.17]), new learning (1.80 points [95% CI, 0.73 to 2.86]), and verbal memory (0.60 points [95% CI, 0.13 to 1.07]). Participants with stroke, compared with those without stroke, demonstrated faster declines in global cognition (0.06 points per year faster [95% CI, 0.03 to 0.08]) and executive function (0.63 points per year faster [95% CI, 0.12 to 1.15]), but not in new learning and verbal memory, compared with prestroke slopes. Among survivors, the difference in risk of cognitive impairment acutely after stroke, compared with immediately before stroke, was not statistically significant (odds ratio, 1.32 [95% CI, 0.95 to 1.83]; P = .10); however, there was a significantly faster poststroke rate of incident cognitive impairment compared with the prestroke rate (odds ratio, 1.23 per year [95% CI, 1.10 to 1.38]; P < .001). For a 70-year-old black woman with average values for all covariates at baseline, stroke at year 3 was associated with greater incident cognitive impairment: absolute difference of 4.0% (95% CI, −1.2% to 9.2%) at year 3 and 12.4% (95% CI, 7.7% to 17.1%) at year 6.CONCLUSIONS AND RELEVANCE Incident stroke was associated with an acute decline in cognitive function and also accelerated and persistent cognitive decline over 6 years.

Background-Recent medical, demographic, and social trends may have had an important impact on the cognitive health of older adults. To assess the impact of these multiple trends, we compared the prevalence and 2-year mortality of cognitive impairment (CI) consistent with dementia in the