Cognitive Aging in Black and White Americans: Cognition, Cognitive Decline, and Incidence of Alzheimer Disease Dementia.

BACKGROUND: US-based studies have reported that older blacks perform worse than older whites on cognitive tests and have higher risk of Alzheimer disease dementia (AD). It is unclear whether these findings reflect differences in cognitive decline. METHODS: The Chicago Health and Aging Project followed individuals, 65+ years old (64% black, 36% white), for up to 18 years. Participants underwent triennial cognitive assessments; stratified randomized samples underwent assessments for AD. We compared black and white participants' cognitive performance, cognitive decline rate (N = 7,735), and AD incidence (N = 2,144), adjusting for age and sex. RESULTS: Black participants performed worse than white participants on the cognitive tests; 441 participants developed AD. Black participants' incident AD risk was twice that of whites (RR = 1.9; 95% CI, 1.4, 2.7), with 58 excess cases/1,000 occurring among blacks (95% CI, 28, 88). Among noncarriers of APOE ε4, blacks had 2.3 times the AD risk (95% CI, 1.5, 3.6), but among carriers, race was not associated with risk (RR = 1.1; 95% CI, 0.6, 2.0; Pinteraction = 0.05). However, cognitive decline was not faster among blacks: the black-white difference in 5-year change in global cognitive score was 0.007 standard unit (95% CI, -0.034, 0.047). Years of education accounted for a sizable portion of racial disparities in cognitive level and AD risk, in analyses using a counterfactual approach. CONCLUSIONS: The higher risk of AD among blacks may stem from lower level of cognitive test performance persisting throughout the observation period rather than faster rate of late-life cognitive decline. Disparities in educational attainment may contribute to these performance disparities. See video abstract at, http://links.lww.com/EDE/B299.

Rate of Cognitive Decline Before and After the Onset of Functional Limitations in Older Persons.

BACKGROUND: Loss in physical function is indicative of deterioration in physiological health that may also be associated with deterioration in neurological health. The objective of this study was to examine whether the onset of functional limitations and their severity is associated with increases in cognitive decline among older adults. METHODS: The study sample consists of 3825 (65% African Americans and 53% females) participants over the age of 65 with no functional limitations. Cognitive function was assessed using a standardized global cognitive score, and functional limitations using a summary measure of 8 Rosow-Breslau and Nagi limitations (ROS-B/Nagi). Cognitive decline before and after the onset of limitations were analyzed using a linear piecewise change point model. RESULTS: During follow-up, 2682 (70%) participants reported limitations in ROS-B/Nagi measure. The rate of cognitive decline was 0.053-units per year before any limitations, and increased to 0.069-units per year after one or more limitations in ROS-B/Nagi measure. This was about 30% (95% Confidence Interval [CI]: 18 - 42%) increase in the rate of cognitive decline comparing before and after the onset of limitations in ROS-B/Nagi measure. Also, higher number of limitations in ROS-B/Nagi measure at the time of onset was associated with faster cognitive decline. CONCLUSIONS: The rate of cognitive decline was significantly higher following functional limitations. This study suggests that self-reported measures of functional limitations may serve as an important marker of cognitive decline.

Deaths in the United States among persons with Alzheimer's disease (2010-2050).

BACKGROUND: Alzheimer's disease (AD) profoundly affects the end-of-life experience. Yet, counts of deaths attributable to AD understate this burden of AD in the population. Therefore, we estimated the annual number of deaths in the United States among older adults with AD from 2010 to 2050. METHODS: We calculated probabilities of AD incidence and mortality from a longitudinal population-based study of 10,802 participants. From this population, 1913 previously disease-free individuals, selected via stratified random sampling, underwent 2577 detailed clinical evaluations. Over the course of follow-up, 990 participants died. We computed age-, sex-, race-, and education-specific AD incidences and education-adjusted AD mortality proportions specific to age, sex, and race group. We then combined these probabilities with US-wide census, education, and mortality data. RESULTS: In 2010, approximately 600,000 deaths occurred among individuals aged 65 years or older with AD, comprising 32% of all older adult deaths. By 2050, this number is projected to be 1.6 million, 43% of all older adult deaths. CONCLUSION: Individuals with AD comprise a substantial number of older adult deaths in the United States, a number expected to rise considerably in coming decades.

Contribution of Alzheimer disease to mortality in the United States.

OBJECTIVE: To assess the burden of mortality attributable to Alzheimer disease (AD) dementia in the United States. METHODS: Data came from 2,566 persons aged 65 years and older (mean 78.1 years) without dementia at baseline from 2 cohort studies of aging with identical annual diagnostic assessments of dementia. Because both studies require organ donation, ascertainment of mortality was complete and dates of death accurate. Mortality hazard ratios (HRs) after incident AD dementia were estimated per 10-year age strata from proportional hazards models. Population attributable risk percentage was derived to estimate excess mortality after a diagnosis of AD dementia. The number of excess deaths attributable to AD dementia in the United States was then estimated. RESULTS: Over an average of 8 years, 559 participants (21.8%) without dementia at baseline developed AD dementia and 1,090 (42.4%) died. Median time from AD dementia diagnosis to death was 3.8 years. The mortality HR for AD dementia was 4.30 (confidence interval = 3.33, 5.58) for ages 75-84 years and 2.77 (confidence interval = 2.37, 3.23) for ages 85 years and older (too few deaths after AD dementia in ages 65-74 were available to estimate HR). Population attributable risk percentage was 37.0% for ages 75-84 and 35.8% for ages 85 and older. An estimated 503,400 deaths in Americans aged 75 years and older were attributable to AD dementia in 2010. CONCLUSIONS: A larger number of deaths are attributable to AD dementia in the United States each year than the number (<84,000 in 2010) reported on death certificates.

Cognitive aging and rate of hospitalization in an urban population of older people.

BACKGROUND: The association of age-related cognitive change with hospitalization is not well understood. METHODS: At 3-year intervals for a mean of 8.7 years, 2,273 older residents of a geographically defined urban community underwent cognitive testing from which a global measure was derived. Hospitalization data were obtained from Part A Medicare beneficiary records. The association of level of cognitive function and rate of cognitive decline in each 3-year interval with subsequent rate of hospitalization was assessed using mixed-effects count regression models. RESULTS: There were 9,091 hospitalizations involving 1,810 of the 2,273 individuals in the cohort (79.6%). Rate of hospitalization increased by 9.7% (95% confidence interval [CI]: 7.2, 12.3) with each additional study year; by 32.7% (95% CI: 26.8, 38.0) for each 1 point lower on the global cognitive measure at the beginning of an observation interval; and by 24.3% (95% CI: 16.6, 32.6) for each 1-point decrease in the global cognitive measure during the previous observation period. These associations persisted after adjustment for comorbidities and exclusion of those with a Mini-Mental State Examination score less than 26. CONCLUSION: Individual differences in trajectories of cognitive aging are associated with subsequent risk of hospitalization.

Alzheimer disease in the United States (2010-2050) estimated using the 2010 census.

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, population-based 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] = 4.0-5.5). Of these, 0.7 million (95% CI = 0.4-0.9) were between 65 and 74 years, 2.3 million were between 75 and 84 years (95% CI = 1.7-2.9), and 1.8 million were 85 years or older (95% CI = 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: The number of people in the United States with AD dementia will increase dramatically in the next 40 years unless preventive measures are developed.

Disability in basic and instrumental activities of daily living is associated with faster rate of decline in cognitive function of older adults.

BACKGROUND: The purpose of this study is to examine whether physical disability is associated with faster rate of decline in cognitive function. METHODS: A longitudinal population-based cohort of 6,678 initially nondisabled older adults from a biracial urban community was interviewed at 3-year intervals from 1993 to 2012. Cognitive function was assessed using a standardized global cognitive score, and physical disabilities using activities of daily living (ADL) and instrumental activities of daily living (IADL). RESULTS: During the follow-up period, 2,450 of 6,678 participants (37%) developed ADL and 2,069 of 4,287 participants (48%) developed IADL disability. After adjusting for demographic and physiologic confounders, cognitive function declined a mean of 0.048 unit per year before ADL disability and 0.047 unit per year before IADL disability. In comparison, the rate of cognitive decline accelerated further by 0.076 unit per year (156% increase) after ADL disability and 0.054 unit per year (115% increase) after IADL disability. Severity of ADL and IADL disabilities were also associated with faster cognitive decline following disability. CONCLUSIONS: In old age, cognitive function declines substantially faster following physical disability even after controlling for demographic and physiologic characteristics of participants.

Cognitive and physical functions as determinants of delayed age at onset and progression of disability.

BACKGROUND: This study examined the association of cognitive and physical functions with age-related transition and progression of activities of daily living (ADL) disability in a population-based longitudinal cohort of nondisabled older adults. METHODS: A longitudinal population-based cohort study of 5,317 initially nondisabled older adults with an average age of 73.6 years of an urban Chicago community were interviewed annually for up to 8 years from 2000 through 2008. Cognitive function was assessed using a standardized global cognitive score and physical function using a combination of measured walk, tandem stand, and chair stand. A novel two-part model was used to access the relationship between cognitive and physical functions and age at onset and progression of ADL disability. RESULTS: The sample consisted of 5,317 participants, 65% blacks, and 61% females. Twenty-five percent reported an onset of ADL disability during follow-up. After adjusting for confounders, lower cognitive and physical functions were associated with an increased risk for lower age at onset. Lower cognitive function was longitudinally associated with increased rate of progression of disability after onset. However, lower physical function did not alter the rate of progression of ADL disability. CONCLUSIONS: Cognitive and physical functions were associated with age at onset. However, only cognitive function was associated with the rate of progression of ADL disability.

Do Community and Caregiver Factors Influence Hospice Use at the End of Life Among Older Adults With Alzheimer Disease?

Hospice is an underused service among people with Alzheimer disease. This study used the Hospice Use Model to examine community, care recipient, and caregiver characteristics associated with hospice use before death among 145 community-dwelling care recipients with Alzheimer disease and their caregivers. Secondary analysis using logistic regression modeling indicated that older age, male gender, black race, and better functional health of care recipients with Alzheimer disease were associated with a decreased likelihood of using hospice (model χ25 = 23.5, P = .0003). Moreover, care recipients recruited from an Alzheimer clinic were more likely to use hospice than those recruited from adult day-care centers. Caregiver factors were not independent predictors of hospice use. However, there was a significant interaction between hours of care provided each week and recruitment site. Among care recipients from the Alzheimer clinic, the probability of hospice use increased as caregiving intensity increased. This relationship was reversed in care recipients from day-care centers. Results suggest that adult day-care centers need to partner with hospice programs in the community. In conclusion, care recipient and community service factors influence hospice use in individuals with Alzheimer disease.

A prospective population-based study of differences in elder self-neglect and mortality between black and white older adults.

BACKGROUND: Self-neglect is the behavior of an elderly person that threatens his or her own health and safety, and it is associated with increased morbidity and mortality. Although report of self-neglect is more common among black older adults, the racial/ethnic differences in mortality remain unclear. METHODS: The Chicago Healthy Aging Project is a population-based cohort study conducted from 1993 to 2005. A subset of these participants were suspected to self-neglect and were reported to a social services agency. Mortality was ascertained during follow-up and from the National Death Index. Cox proportional hazards models were used to assess the mortality risk. RESULTS: In the total cohort, there were 5,963 black and 3,475 white older adults, and of these, 1,479 were reported for self-neglect (21.7% in black and 5.3% in white older adults). In multivariable analyses with extensive adjustments, the interaction term indicated that impact of self-neglect on mortality was significantly stronger in black than in white older adults (parameter estimate, 0.54, SE, 0.14, p < .001). This difference persisted over time. In race/ethnicity-stratified analyses, at 6 months after report of self-neglect, the hazard ratio for black older adults was 5.00 (95% confidence interval, 4.47-5.59) and for white older adults was 2.75 (95% confidence interval, 2.19-3.44). At 3 years after report, the hazard ratios were 2.61 (95% confidence interval, 2.25-3.04) and 1.47 (95% confidence interval, 1.10-1.96) for black older adults and white older adults, respectively. CONCLUSIONS: Future studies are needed to qualify the casual mechanisms between self-neglect and mortality in black and white older adults in order to devise targeted prevention and intervention strategies.

Racial differences in the association of education with physical and cognitive function in older blacks and whites.

OBJECTIVES: Few studies have explicitly tested whether the health disadvantage among older blacks is consistent across the entire range of education. We examined racial differences in the cross-sectional association of education with physical and cognitive function performance in older adults. METHODS: Participants included over 9500 blacks and whites, aged ≥ 65 years, from the Chicago Health and Aging Project {64% black, 60% women, mean age = 73.0 (standard deviation [SD] = 6.9), mean education = 12.2 (SD = 3.5)}. Physical function was assessed using 3 physical performance tests, and cognitive function was assessed with 4 performance-based tests; composite measures were created and used in analyses. RESULTS: In multiple regression models that controlled for age, age-squared, sex, and race, and their interactions, whites and those with higher education (>12 years) performed significantly better on both functional health measures. The association of education with each indicator of functional health was similar in older blacks and whites with low levels (≤ 12 years) of education. However, at higher levels of education, there was a significantly more positive association between years of education and these functional health outcomes among blacks than whites. DISCUSSION: Results from this biracial population-based sample in the Midwest suggest that blacks may enjoy greater returns in functional health for additional education beyond high school.

Sources of variability in estimates of the prevalence of Alzheimer's disease in the United States.

BACKGROUND: The prevalence of Alzheimer's disease (AD) in the United States was estimated at 2.3 million in 2002 by the Aging, Demographics, and Memory Study (ADAMS), which is almost 50% less than the estimate of 4.5 million in 2000 derived from the Chicago Health and Aging Project. METHODS: We considered how differences in diagnostic criteria may have contributed to these differences in AD prevalence. RESULTS: We identified several important differences in diagnostic criteria that may have contributed to the differing estimates of AD prevalence. Two factors were especially noteworthy. First, the Diagnostic and Statistical Manual of Mental Disorders III-R and IV criteria of functional limitation documented by an informant used in ADAMS effectively concentrated the diagnosis of dementia toward a relatively higher level of cognitive impairment. ADAMS separately identified a category of cognitive impairment not dementia and within that group there were a substantial number of cases with "prodromal" AD (a maximum of 1.95 million with upweighting). Second, a substantial proportion of dementia in ADAMS was attributed to either vascular disease (representing a maximum of 0.59 million with upweighting) or undetermined etiology (a maximum of 0.34 million), whereas most dementia, including mixed dementia, was attributed to AD in the Chicago Health and Aging Project. CONCLUSION: The diagnosis of AD in population studies is a complex process. When a diagnosis of AD excludes persons meeting criteria for vascular dementia, when not all persons with dementia are assigned an etiology, and when a diagnosis of dementia requires an informant report of functional limitations, the prevalence is substantially lower and the diagnosed cases most likely have a relatively higher level of impairment.

Trends in the incidence and prevalence of Alzheimer's disease, dementia, and cognitive impairment in the United States.

Declines in heart disease and stroke mortality rates are conventionally attributed to reductions in cigarette smoking, recognition and treatment of hypertension and diabetes, effective medications to improve serum lipid levels and to reduce clot formation, and general lifestyle improvements. Recent evidence implicates these and other cerebrovascular factors in the development of a substantial proportion of dementia cases. Analyses were undertaken to determine whether corresponding declines in age-specific prevalence and incidence rates for dementia and cognitive impairment have occurred in recent years. Data spanning 1 or 2 decades were examined from community-based epidemiological studies in Minnesota, Illinois, and Indiana, and from the Health and Retirement Study, which is a national survey. Although some decline was observed in the Minnesota cohort, no statistically significant trends were apparent in the community studies. A significant reduction in cognitive impairment measured by neuropsychological testing was identified in the national survey. Cautious optimism appears justified.

Upper and lower extremity motor performance and functional impairment in Alzheimer's disease.

This report examines the relation of upper and lower extremity motor performance to functional impairment among 371 persons with probable Alzheimer's disease (AD). Cognitive and motor performance tests were administered at 6-month intervals for up to 4 years. Motor performance was assessed using 3 lower extremity tests and 2 upper extremity tests. Functional impairment was measured at 3-month intervals using caregiver ratings of impairments in activities of daily living, mobility, and range of motion. Both lower and upper extremity performance were inversely related to functional impairments on all 3 scales (all Ps < .001), after controlling for age, sex, and level of cognitive impairment. This suggests that motor performance contributes to functional impairments in AD, independent of cognitive impairment. It is important to preserve motor performance in individuals with AD because it influences physical function throughout the course of the disease.

Change in direct measures of physical performance among persons with Alzheimer's disease.

OBJECTIVES: Measures of physical performance were used in intact and community populations. We examined upper and lower extremity physical performance tests among people with Alzheimer's disease. METHOD: A total of 367 persons with probable Alzheimer's disease, recruited from an Alzheimer's disease diagnostic center, were given three tests of lower extremity function and two tests of upper extremity function at 6 month intervals for up to 4 years. Gender, race, age and Mini-Mental State Examination (MMSE) score at baseline were used to predict subsequent decline in composite scores of lower and upper extremity function. RESULTS: At baseline, older age and lower MMSE scores were associated with lower scores on both lower and upper extremity function. Males performed better at baseline on lower extremity tests only. For each point higher on MMSE, a person declined 0.023 Standard Unit (SU) less per year (p = 0.0001) on lower extremity tests and declined 0.019 SU less per year (p < 0.0001) on upper extremity tests. CONCLUSION: Physical performance was measured across a range of disease severities and declined over time. Lower cognitive score at baseline predicted faster decline in both lower and upper extremity function. Demographic heterogeneity in decline suggests other predictors may identify factors protective against physical decline.

The effect of adult day care services on time to nursing home placement in older adults with Alzheimer's disease.

PURPOSE: This longitudinal study examined whether the use of adult day care services delayed time to nursing home placement in persons with Alzheimer's disease. DESIGN AND METHODS: Two hundred and eighteen adult day care clients with Alzheimer's disease were recruited from 16 adult day programs in a large metropolitan area. Two hundred and ninety eight persons with Alzheimer's disease but not using adult day care were recruited from a federally funded Alzheimer's diagnostic center and frequency matched to adult day care users on age, gender, race, and level of cognitive impairment. Participants were followed at 3-month intervals for up to 48 months. Cox proportional hazards models were used to examine the effects of adult day care and other fixed and time-varying factors on risk of nursing home placement. RESULTS: Risk of nursing home placement increased significantly with the number of days of adult day care attendance, with this effect being substantially greater for men (hazard ratio or HR = 1.33; confidence interval or CI = 1.18-1.49) than for women (HR = 1.09; CI = 1.00-1.18). Participant disability and hospitalizations and caregiver age and burden were independent predictors, but their inclusion in the model did not alter the risk associated with adult day care. IMPLICATIONS: More severe disease and greater caregiver burden did not explain the increased risk of nursing home placement among adult day care users with Alzheimer's disease. Rather, it appears that other unmeasured factors, such as a proclivity to institutionalize, may account for the association of adult day care to nursing home risk.

Dietary folate and vitamin B12 intake and cognitive decline among community-dwelling older persons.

BACKGROUND: Deficiencies in folate and vitamin B12 have been associated with neurodegenerative disease. OBJECTIVE: To examine the association between rates of age-related cognitive change and dietary intakes of folate and vitamin B12. DESIGN: Prospective study performed from 1993 to 2002. SETTING: Geographically defined biracial community in Chicago, Ill. PARTICIPANTS: A total of 3718 residents, 65 years and older, who completed 2 to 3 cognitive assessments and a food frequency questionnaire. MAIN OUTCOME MEASURE: Change in cognitive function measured at baseline and 3-year and 6-year follow-ups, using the average z score of 4 tests: the East Boston Tests of immediate and delayed recall, the Mini-Mental State Examination, and the Symbol Digit Modalities Test. RESULTS: High folate intake was associated with a faster rate of cognitive decline in mixed models adjusted for multiple risk factors. The rate of cognitive decline among persons in the top fifth of total folate intake (median, 742 microg/d) was more than twice that of those in the lowest fifth of intake (median, 186 microg/d), a statistically significant difference of 0.02 standardized unit per year (P = .002). A faster rate of cognitive decline was also associated with high folate intake from food (P for trend = .04) and with folate vitamin supplementation of more than 400 microg/d compared with nonusers (beta = -.03, P<.001). High total B12 intake was associated with slower cognitive decline only among the oldest participants. CONCLUSIONS: High intake of folate may be associated with cognitive decline in older persons. These unexpected findings call for further study of the cognitive implications of high levels of dietary folate in older populations.

Predictors of beginning and ending caregiving during a 3-year period in a biracial community population of older adults.

OBJECTIVES: We sought to identify predictors of beginning and ending caregiving. METHODS: At baseline and 3-year follow-up, we interviewed 4245 community residents (61.4% Black, 38.4% White, 0.20% other) aged 65 years or older. We used logistic regression to test predictors of beginning caregiving among baseline noncaregivers and of continuing caregiving among baseline caregivers. RESULTS: After control for demographic variables, physically healthier individuals were significantly more likely to become caregivers and to continue caregiving. Mental health had little influence on beginning caregiving, but declining mental heath was associated with continuing caregiving. CONCLUSIONS: Maintenance of physical health and function is essential to the ability of older adults to begin and to continue caregiving. Studies that compare the health of current caregivers with that of noncaregivers may substantially underestimate the impact of caregiving on health.