Objectives: To provide updated estimates of Alzheimer disease (AD) dementia prevalence in the United States from 2010 through 2050.Methods: Probabilities of AD dementia incidence were calculated from a longitudinal, populationbased study including substantial numbers of both black and white participants. Incidence probabilities for single year of age, race, and level of education were calculated using weighted logistic regression and AD dementia diagnosis from 2,577 detailed clinical evaluations of 1,913 people obtained from stratified random samples of previously disease-free individuals in a population of 10,800. These were combined with US mortality, education, and new US Census Bureau estimates of current and future population to estimate current and future numbers of people with AD dementia in the United States.Results: We estimated that in 2010, there were 4.7 million individuals aged 65 years or older with AD dementia (95% confidence interval [CI] 5 4.0-5.5). Of these, 0.7 million (95% CI 5 0.4-0.9) were between 65 and 74 years, 2.3 million were between 75 and 84 years (95% CI 5 1.7-2.9), and 1.8 million were 85 years or older (95% CI 5 1.4-2.2). The total number of people with AD dementia in 2050 is projected to be 13.8 million, with 7.0 million aged 85 years or older. Conclusion:

This report describes the public health impact of Alzheimer's disease, including incidence and prevalence, mortality rates, costs of care, and the overall impact on caregivers and society. It also examines in detail the financial impact of Alzheimer's on families, including annual costs to families and the difficult decisions families must often make to pay those costs. An estimated 5.4 million Americans have Alzheimer's disease. By mid-century, the number of people living with Alzheimer's disease in the United States is projected to grow to 13.8 million, fueled in large part by the aging baby boom generation. Today, someone in the country develops Alzheimer's disease every 66 seconds. By 2050, one new case of Alzheimer's is expected to develop every 33 seconds, resulting in nearly 1 million new cases per year. In 2013, official death certificates recorded 84,767 deaths from Alzheimer's disease, making it the sixth leading cause of death in the United States and the fifth leading cause of death in Americans age ≥ 65 years. Between 2000 and 2013, deaths resulting from stroke, heart disease, and prostate cancer decreased 23%, 14%, and 11%, respectively, whereas deaths from Alzheimer's disease increased 71%. The actual number of deaths to which Alzheimer's disease contributes is likely much larger than the number of deaths from Alzheimer's disease recorded on death certificates. In 2016, an estimated 700,000 Americans age ≥ 65 years will die with Alzheimer's disease, and many of them will die because of the complications caused by Alzheimer's disease. In 2015, more than 15 million family members and other unpaid caregivers provided an estimated 18.1 billion hours of care to people with Alzheimer's and other dementias, a contribution valued at more than $221 billion. Average per-person Medicare payments for services to beneficiaries age ≥ 65 years with Alzheimer's disease and other dementias are more than two and a half times as great as payments for all beneficiaries without these conditions, and Medicaid payments are 19 times as great. Total payments in 2016 for health care, long-term care and hospice services for people age ≥ 65 years with dementia are estimated to be $236 billion. The costs of Alzheimer's care may place a substantial financial burden on families, who often have to take money out of their retirement savings, cut back on buying food, and reduce their own trips to the doctor. In addition, many family members incorrectly believe that Medicare pays for nursing home care and other types of long-term care. Such findings highlight the need for solutions to prevent dementia-related costs from jeopardizing the health and financial security of the families of people with Alzheimer's and other dementias.

IMPORTANCE Players of American football may be at increased risk of long-term neurological conditions, particularly chronic traumatic encephalopathy (CTE). OBJECTIVE To determine the neuropathological and clinical features of deceased football players with CTE. DESIGN, SETTING, AND PARTICIPANTS Case series of 202 football players whose brains were donated for research. Neuropathological evaluations and retrospective telephone clinical assessments (including head trauma history) with informants were performed blinded. Online questionnaires ascertained athletic and military history. EXPOSURES Participation in American football at any level of play. MAIN OUTCOMES AND MEASURES Neuropathological diagnoses of neurodegenerative diseases, including CTE, based on defined diagnostic criteria; CTE neuropathological severity (stages I to IV or dichotomized into mild [stages I and II] and severe [stages III and IV]); informant-reported athletic history and, for players who died in 2014 or later, clinical presentation, including behavior, mood, and cognitive symptoms and dementia. RESULTS Among 202 deceased former football players (median age at death, 66 years [interquartile range, 47–76 years]), CTE was neuropathologically diagnosed in 177 players (87%; median age at death, 67 years [interquartile range, 52–77 years]; mean years of football participation, 15.1 [SD, 5.2]), including 0 of 2 pre–high school, 3 of 14 high school (21%), 48 of 53 college (91%), 9 of 14 semiprofessional (64%), 7 of 8 Canadian Football League (88%), and 110 of 111 National Football League (99%) players. Neuropathological severity of CTE was distributed across the highest level of play, with all 3 former high school players having mild pathology and the majority of former college (27 [56%]), semiprofessional (5 [56%]), and professional (101 [86%]) players having severe pathology. Among 27 participants with mild CTE pathology, 26 (96%) had behavioral or mood symptoms or both, 23 (85%) had cognitive symptoms, and 9 (33%) had signs of dementia. Among 84 participants with severe CTE pathology, 75 (89%) had behavioral or mood symptoms or both, 80 (95%) had cognitive symptoms, and 71 (85%) had signs of dementia. CONCLUSIONS AND RELEVANCE In a convenience sample of deceased football players who donated their brains for research, a high proportion had neuropathological evidence of CTE, suggesting that CTE may be related to prior participation in football.

Context Physical activity may help maintain cognitive function in older adults. Objective To examine the relation of long-term regular physical activity, including walking, to cognitive function. Design Women reported participation in leisure-time physical activities on biennial mailed questionnaires beginning in 1986. We assessed long-term activity by averaging energy expenditures from questionnaires in 1986 through participants' baseline cognitive assessments (1995 to 2001). We used linear regression to estimate adjusted mean differences in baseline cognitive performance and cognitive decline over 2 years, across levels of physical activity and walking. Setting and Participants Nurses' Health Study, including 18766 US women aged 70 to 81 years. Main Outcome Measure Validated telephone assessments of cognition administered twice approximately 2 years apart (1995 to 2001 and 1997 to 2003), including tests of general cognition, verbal memory, category fluency, and attention. Results Higher levels of activity were associated with better cognitive performance. On a global score combining results of all 6 tests, women in the second through fifth quintiles of energy expenditure scored an average of 0.06, 0.06, 0.09, and 0.10 standard units higher than women in the lowest quintile (P for trend Ͻ.001). Compared with women in the lowest physical activity quintile, we found a 20% lower risk of cognitive impairment for women in the highest quintile of activity. Among women performing the equivalent of walking at an easy pace for at least 1.5 h/wk, mean global scores were 0.06 to 0.07 units higher compared with walking less than 40 min/wk (PՅ.003). We also observed less cognitive decline among women who were more active, especially those in the 2 highest quintiles of energy expenditure. Women in the fourth and fifth quintiles had mean changes in global scores that were 0.04 (95% confidence interval, 0.02-0.10) and 0.06 (95% confidence interval, 0.02-0.11) standard units better than those in the lowest quintile. Conclusion Long-term regular physical activity, including walking, is associated with significantly better cognitive function and less cognitive decline in older women.

In research on the determinants of change in health status, a crucial analytic decision is whether to adjust for baseline health status. In this paper, the authors examine the consequences of baseline adjustment, using for illustration the question of the effect of educational attainment on change in cognitive function in old age. With data from the US-based Assets and Health Dynamics Among the Oldest Old survey (n = 5,726; born before 1924), they show that adjustment for baseline cognitive test score substantially inflates regression coefficient estimates for the effect of schooling on change in cognitive test scores compared with models without baseline adjustment. To explain this finding, they consider various plausible assumptions about relations among variables. Each set of assumptions is represented by a causal diagram. The authors apply simple rules for assessing causal diagrams to demonstrate that, in many plausible situations, baseline adjustment induces a spurious statistical association between education and change in cognitive score. More generally, when exposures are associated with baseline health status, this bias can arise if change in health status preceded baseline assessment or if the dependent variable measurement is unreliable or unstable. In some cases, change-score analyses without baseline adjustment provide unbiased causal effect estimates when baseline-adjusted estimates are biased.

Background The red cell distribution width (RDW), an automated measure of red blood cell size heterogeneity (e.g. anisocytosis) that is largely overlooked, is a newly recognized risk marker in patients with established cardiovascular disease (CVD). It is unknown whether RDW is associated with mortality in the general population, or whether this association is specific to CVD. Methods We examined the association of RDW with all-cause mortality, as well as cardiovascular, cancer, and chronic lower respiratory disease mortality among 15,852 adult participants in The Third National Health and Nutrition Examination Survey (1988–1994), a nationally representative sample of the United States population. Mortality status was obtained by matching to the National Death Index, with follow-up through December 31, 2000. Results Estimated mortality rates increased 5-fold from the lowest to highest quintile of RDW after accounting for age, and 2-fold after multivariable adjustment (each Ptrend < 0.001). A 1- standard deviation increment in RDW (0.98) was associated with a 23% greater risk of all-cause mortality (hazard ratio (HR) 1.23, 95% confidence interval (CI) 1.18–1.28) after multivariable adjustment. RDW was also associated with risk of death due to cardiovascular disease (HR 1.22, 95% CI 1.14–1.31), cancer (HR 1.28, 95% CI 1.21–1.36), and chronic lower respiratory disease (HR 1.32, 95% CI 1.17–1.49). Conclusions Higher RDW was associated with increased mortality risk in this large, community-based sample, an association not specific to CVD. Study of anisocytosis may therefore yield novel pathophysiological insights, and measurement of RDW may contribute to risk assessment.

Background Chronic exposure to particulate air pollution may accelerate cognitive decline in older adults, although data on this association are limited. Our objective was to examine long-term exposure to particulate matter (PM) air pollution, both coarse ([PM 2.5–10 μm in diameter [PM2.5-10]) and fine (PM <2.5 μm in diameter [PM2.5]), in relation to cognitive decline. Methods The study population comprised the Nurses’ Health Study Cognitive Cohort, which included 19 409 US women aged 70 to 81 years. We used geographic information system–based spatiotemporal smoothing models to estimate recent (1 month) and long-term (7–14 years) exposures to PM2.5-10, and PM2.5 preceding base-line cognitive testing (1995–2001) of participants residing in the contiguous United States. We used generalized estimating equation regression to estimate differences in the rate of cognitive decline across levels of PM2.5-10 and PM2.5 exposures. The main outcome measure was cognition, via validated telephone assessments, administered 3 times at approximately 2-year intervals, including tests of general cognition, verbal memory, category fluency, working memory, and attention. Results Higher levels of long-term exposure to both PM2.5-10 and PM2.5 were associated with significantly faster cognitive decline. Two-year decline on a global score was 0.020 (95% CI, −0.032 to −0.008) standard units worse per 10 μg/m3 increment in PM2.5-10 exposure and 0.018 (95% CI, −0.035 to −0.002) units worse per 10 μg/m3 increment in PM2.5 exposure. These differences in cognitive trajectory were similar to those between women in our cohort who were approximately 2 years apart in age, indicating that the effect of a 10-μg/m3 increment in long-term PM exposure is cognitively equivalent to aging by approximately 2 years. Conclusion Long-term exposure to PM2.5-10 and PM2.5 at levels typically experienced by many individuals in the United States is associated with significantly worse cognitive decline in older women.

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