Statins, incident Alzheimer disease, change in cognitive function, and neuropathology

OBJECTIVE

To examine the relation of statins to incident Alzheimer disease (AD) and change in cognition and neuropathology.

METHODS

Participants were 929 older Catholic clergy (68.7% women, mean baseline age 74.9 years, education 18.2 years, Mini-Mental State Examination 28.5) free of dementia, enrolled in the Religious Orders Study, a longitudinal clinical-pathologic study of AD. All agreed to brain autopsy at time of death and underwent annual structured clinical evaluations, allowing for classification of AD and assessment of cognition (based on 19 neuropsychological tests). Statins were identified by direct medication inspection. Neuropathologic data were available on 262 participants. All macroscopic chronic cerebral infarctions were recorded. A measure of global AD pathology was derived from silver stain, and separate measures of amyloid and tangles were based on immunohistochemistry. We examined the relation of statins to incident AD using Cox proportional hazards, change in cognition using mixed effects models, and pathologic indices using logistic and linear regression.

RESULTS

Statin use at baseline (12.8%) was not associated with incident AD (191 persons, up to 12 follow-up years), change in global cognition, or five separate cognitive domains (all p values > 0.20). Statin use any time prior to death (17.9%) was not related to global AD pathology. Persons taking statins were less likely to have amyloid (p = 0.02). However, among those with amyloid, there was no relation of statins to amyloid load. Statins were not related to tangles or infarction.

CONCLUSIONS

Overall, statins were not related to incident Alzheimer disease (AD) or change in cognition, or continuous measures of AD pathology or infarction.

Body mass index and cognitive decline in a biracial community population

OBJECTIVE

To examine whether a higher body mass index (BMI) in older adults is associated with greater cognitive decline.

METHODS

A longitudinal study was conducted from 1993 to 2003 with an average follow-up of 6.4 years of a biracial community population on the south side of Chicago. Participants were 3,885 community-dwelling adults aged 65 and older who participated in at least two assessments. A composite measure of global cognitive function was used which was derived from the average of standardized scores from four cognitive tests.

RESULTS

There was a significant curvilinear association between BMI and cognitive function scores at baseline for both black (= -0.0014, p = 0.001) and non-black subjects (= -0.0011, p = 0.002). In a mixed model adjusted for age, sex, race, and education, higher BMI was associated with less cognitive decline in both black (= 0.0013, p = 0.009) and non-black subjects (= 0.0021, p = 0.006). Adjusting for comorbid illnesses did not change these findings substantially. However, the associations were much smaller and no longer significant among participants with no cognitive decline at baseline as measured by a Mini-Mental State Examination score of greater than 24.

CONCLUSIONS

The findings suggest that greater body mass index in old age is not predictive of cognitive decline in a cognitively unimpaired community population.

Relation of cognitive activity to risk of developing Alzheimer disease

BACKGROUND

Frequent cognitive activity in old age has been associated with reduced risk of Alzheimer disease (AD), but the basis of the association is uncertain.

METHODS

More than 700 old people underwent annual clinical evaluations for up to 5 years. At baseline, they rated current and past frequency of cognitive activity with the current activity measure administered annually thereafter. Those who died underwent a uniform postmortem examination of the brain. Amyloid burden, density of tangles, and presence of Lewy bodies were assessed in eight brain regions and the number of chronic cerebral infarctions was noted.

RESULTS

During follow-up, 90 people developed AD. More frequent participation in cognitive activity was associated with reduced incidence of AD (HR = 0.58; 95% CI: 0.44, 0.77); a cognitively inactive person (score = 2.2, 10th percentile) was 2.6 times more likely to develop AD than a cognitively active person (score = 4.0, 90th percentile). The association remained after controlling for past cognitive activity, lifespan socioeconomic status, current social and physical activity, and low baseline cognitive function. Frequent cognitive activity was also associated with reduced incidence of mild cognitive impairment and less rapid decline in cognitive function. Among 102 persons who died and had a brain autopsy, neither global nor regionally specific measures of neuropathology were related to level of cognitive activity before the study, at study onset, or during the course of the study.

CONCLUSION

Level of cognitively stimulating activity in old age is related to risk of developing dementia.

Chronic distress and incidence of mild cognitive impairment

OBJECTIVE

Mild cognitive impairment (MCI) is associated with increased morbidity and mortality but its development is not well understood. Here we test the hypothesis that chronic psychological distress is associated with increased incidence of MCI in old age.

METHODS

Participants are older persons from two cohort studies with uniform annual clinical evaluations which included detailed cognitive testing and clinical classification of MCI. We excluded persons with dementia or MCI at baseline; follow-up data were available on 1,256 persons without cognitive impairment (95% of those eligible). At baseline, they completed a six-item measure of neuroticism (mean = 15.6, SD = 6.6), an indicator of the tendency to experience psychological distress.

RESULTS

During up to 12 years of follow-up, 482 persons (38%) developed MCI. Risk of MCI increased by about 2% for each one unit increase on the distress scale (relative risk [RR] = 1.02; 95% CI: 1.01, 1.04), with the association slightly stronger in men than women. Overall, a distress-prone person (score = 24, 90th percentile) was about 40% more likely to develop MCI than someone not prone to distress (score = 8, 10th percentile). Adjustment for depressive symptomatology at baseline did not substantially change results (RR = 1.02; 95% CI: 1.00, 1.03). Depressive symptoms were also related to risk of MCI but not after controlling for distress score. In mixed-effects models, higher distress score was associated with lower level of function in multiple cognitive domains at baseline and more rapid cognitive decline, especially in episodic memory.

CONCLUSION

Among older persons without manifest cognitive impairment, higher level of chronic psychological distress is associated with increased incidence of mild cognitive impairment.

Lower Extremity Motor Function and Disability in Mild Cognitive Impairment

Recent findings suggest that lower extremity motor dysfunction may be a feature of mild cognitive impairment (MCI), but little is known about the nature and significance of lower extremity motor dysfunction in MCI. The aim of this study was to examine the extent to which MCI is associated with impaired gait, balance, and strength and to examine the relation of lower extremity function to disability among persons with MCI in the Rush Memory and Aging Project, a clinical-pathologic study of common chronic conditions of old age. In a series of analyses adjusted for age, sex, and education, individuals with MCI exhibited more impaired gait and balance than individuals without cognitive impairment. Because vascular factors can contribute to lower extremity motor dysfunction, the authors repeated the initial analyses including terms for vascular risk factors and vascular disease, and the associations between MCI and lower extremity motor dysfunction persisted. Moreover, among those with MCI, impairments in gait and balance were associated with an increased likelihood of disability. These findings suggest that lower extremity motor dysfunction is common and contributes to disability in MCI, but lower extremity motor dysfunction in MCI does not appear to be explained by the vascular factors examined in this study.

Physical activity and motor decline in older persons

We tested the hypothesis that physical activity modifies the course of age-related motor decline. More than 850 older participants of the Rush Memory and Aging Project underwent baseline assessment of physical activity and annual motor testing for up to 8 years. Nine strength measures and nine motor performance measures were summarized into composite measures of motor function. In generalized estimating equation models, global motor function declined during follow-up (estimate, -0.072; SE, 0.008; P < 0.001). Each additional hour of physical activity at baseline was associated with about a 5% decrease in the rate of global motor function decline (estimate, 0.004; SE, 0.001; P = 0.007). Secondary analyses suggested that the association of physical activity with motor decline was mostly due to the effect of physical activity on the rate of motor performance decline. Thus, higher levels of physical activity are associated with a slower rate of motor decline in older persons.

Diabetes is related to cerebral infarction but not to AD pathology in older persons

OBJECTIVE

To examine the potential relation of diabetes to common neuropathologic causes of dementia, cerebral infarction and Alzheimer disease (AD) neuropathology.

METHODS

Subjects were 233 older Catholic clergy in the Religious Orders Study, who underwent detailed annual evaluations, including neuropsychological testing, and brain autopsy at time of death (mean age 86 years, 45% men). Diabetes was identified by annual direct medication inspection and history. Cognitive function proximate to death was summarized into five cognitive domains, based on 19 neuropsychological tests. Macroscopic cerebral infarctions were recorded from 1 cm coronal slabs. Neuritic plaques, diffuse plaques, and neurofibrillary tangles were counted in Bielschowsky silver-stained sections and summarized to yield composite measures of neuritic plaques, diffuse plaques, tangles, and overall AD pathology. We also used immunohistochemistry with antibodies to amyloid-beta and PHF-tau to obtain quantitative measures of amyloid burden and neurofibrillary tangle density. Multiple logistic and linear regression analyses were used to examine the relation of diabetes to cerebral infarctions and AD pathology, controlling for age, sex, and education.

RESULTS

AD pathology was related to all five cognitive domains (p < 0.01) and infarctions were related to perceptual speed (p < 0.001). Diabetes (present in 15% subjects) was associated with an increased odds of infarction (OR = 2.47, 95% CI: 1.16, 5.24). Diabetes was not related to global AD pathology score, or to specific measures of neuritic plaques, diffuse plaques or tangles, or to amyloid burden or tangle density.

CONCLUSION

We found a relation between diabetes and cerebral infarction but not between diabetes and Alzheimer disease pathology in older persons.

Body mass index in older persons is associated with Alzheimer disease pathology

OBJECTIVE

We examined the extent to which body mass index (BMI) in older persons is associated with common age-related neuropathologies known to contribute to dementia including Alzheimer disease (AD) pathology, cerebral infarction, and Lewy body disease.

METHODS

We studied brain autopsies from 298 deceased Catholic clergy participating in the Religious Orders Study, a longitudinal clinical-pathologic investigation. BMI was assessed at annual clinical evaluations during an average follow-up of 4.9 years (SD = 2.7 years). Each person's average BMI, derived from all evaluations, was used in analyses. Multiple regression analyses were used to examine the relation of common postmortem neuropathologic findings to average BMI prior to death.

RESULTS

Mean age at death was 85.7 years (SD = 6.8 years), and average BMI during the course of the study was 26.0 (SD = 5.1). A series of linear regression models was performed with average BMI as the outcome and controlling for age, sex, and education. Level of AD pathology was associated with BMI proximate to death (estimate = -1.15; SE = 0.42; p = 0.007). However, Lewy body pathology (estimate = -0.45; SE = 0.73; p = 0.53) and cerebral infarctions (estimate = -0.10; SE = 0.61; p = 0.88) were not associated with average BMI. The association of AD pathology with BMI was unchanged after controlling for dementia, chronic diseases, and physical activity.

CONCLUSION

Body mass in old age is associated with Alzheimer disease pathology in persons with and without dementia.

The relationship between cerebral Alzheimer's disease pathology and odour identification in old age

BACKGROUND

Olfactory dysfunction is common in old age, but its basis is uncertain.

OBJECTIVE

To test the hypothesis that difficulty in identifying odours in old age is related to the accumulation of Alzheimer's disease pathology.

METHODS

As part of the Rush Memory and Aging Project, participants completed the 12-item Brief Smell Identification Test, a standard measure of odour identification. During a mean (standard deviation (SD)) of 2.2 (1.2) years of follow-up (range 0.2-4.9), 166 people died, with brain autopsies performed on 129 (77.7%) people and neuropathological examinations completed on 77 (mean (SD) age at death 87.5 (5.9) years; median postmortem interval 6.1 h). From a uniform postmortem examination of multiple brain regions, summary measures of plaque and tangle pathology were derived on the basis of silver staining, and those of amyloid beta burden, tangle density and Lewy bodies on the basis of immunohistochemistry.

RESULTS

Odour identification performance ranged from 0 to 12 correct (mean (SD) 8.0 (2.6)). In analyses adjusted for age, sex and education, a composite measure of plaques and tangles accounted for >12% of the variation in odour identification. The association remained after controlling for dementia or semantic memory. Density of tau tangles was inversely related to odour identification. A similar effect for amyloid burden was attenuated after controlling for tangles. The association with odour identification was robust for tangles in the entorhinal cortex and CA1/subiculum area of the hippocampus, but not for tangles in other cortical sites. Lewy bodies, identified in 12.5%, were not related to odour identification, probably partly due to to their relative infrequency.

CONCLUSION

The results suggest that difficulty in identifying familiar odours in old age is partly due to the accumulation of neurofibrillar pathology in central olfactory regions.

Associations of vegetable and fruit consumption with age-related cognitive change

OBJECTIVE

To examine the association between rates of cognitive change and dietary consumption of fruits and vegetables among older persons.

METHODS

The authors conducted a prospective cohort study of 3,718 participants, aged 65 years and older of the Chicago Health and Aging Project. Participants completed a food frequency questionnaire and were administered at least two of three cognitive assessments at baseline, 3-year, and 6-year follow-ups. Cognitive function was measured using the average z-score of four tests: the East Boston Tests of immediate memory and delayed recall, the Mini-Mental State Examination, and the Symbol Digit Modalities Test.

RESULTS

The mean cognitive score at baseline for the analyzed cohort was 0.18 (range: -3.5 to 1.6), and the overall mean change in score per year was a decline of 0.04 standardized units. In mixed effects models adjusted for age, sex, race, and education, compared with the rate of cognitive decline among persons in the lowest quintile of vegetable intake (median of 0.9 servings/day), the rate for persons in the fourth quintile (median, 2.8 servings/day) was slower by 0.019 standardized units per year (p = 0.01), a 40% decrease, and by 0.018 standardized units per year (p = 0.02) for the fifth quintile (median, 4.1 servings/day), or a 38% decrease in rates. The association remained significant (p for linear trend = 0.02) with further control of cardiovascular-related conditions and risk factors. Fruit consumption was not associated with cognitive change.

CONCLUSION

High vegetable but not fruit consumption may be associated with slower rate of cognitive decline with older age.

Substantial changes in the genetic basis of tadpole morphology of Rana lessonae in the presence of predators

Predator-induced morphological plasticity is a model system for investigating phenotypic plasticity in an ecological context. We investigated the genetic basis of the predator-induced plasticity in Rana lessonae by determining the pattern of genetic covariation of three morphological traits that were found to be induced in a predatory environment. Body size decreased and tail dimensions increased when reared in the presence of preying dragonfly larvae. Genetic variance in body size increased by almost an order of magnitude in the predator environment, and the first genetic principal component was found to be highly significantly different between the two environments. The across environment genetic correlation for body size was significantly below 1 indicating that different genes contributed to this trait in the two environments. Body size may therefore be able to respond to selection independently in the two environments to some extent.

Mild cognitive impairment: Risk of Alzheimer disease and rate of cognitive decline

OBJECTIVE

To examine the extent to which persons with mild cognitive impairment (MCI) have an increased risk of Alzheimer disease (AD) and a more rapid rate of decline in cognitive function compared to similar persons without cognitive impairment.

METHOD

Participants were 786 community-based persons (221 with MCI and 565 without cognitive impairment) from the Rush Memory and Aging Project, an ongoing longitudinal clinical-pathologic study of common chronic conditions of old age. All participants underwent detailed annual clinical and neuropsychological evaluations. The authors examined the risk of incident AD and rate of change in global cognitive function among persons with MCI and those without cognitive impairment; all statistical models controlled for age, sex, and education.

RESULTS

Over an average of 2.5 years of follow-up, 57 persons with MCI (25.8%) developed AD, a rate 6.7 times higher than those without cognitive impairment. In addition, persons with MCI declined considerably more rapidly each year on a measure of global cognitive function than those without cognitive impairment.

CONCLUSIONS

Mild cognitive impairment is associated with a greatly increased risk of incident Alzheimer disease and a more rapid rate of decline in cognitive function.

Diabetes mellitus, dementia, and cognitive function in older persons

Dementia and cognitive decline are among the most common and most feared conditions of old age making the identification of modifiable risk factors for dementia an urgent public health priority. Recently, an increasing body of data suggests that type 2 diabetes mellitus, a common condition in older persons, is associated with the development of dementia and cognitive decline. A systematic review of the medical literature of the past 15 years identified 40 original-report articles in the English language pertaining to the relation of diabetes to dementia and cognitive function in older persons. Most, but not all, of these studies suggest a detrimental effect of diabetes on cognitive function. Current research efforts are aimed at understanding the underlying neurobiologic mechanisms whereby diabetes causes dementia and cognitive impairment in order to develop rational interventions to prevent this recently documented adverse consequence.

Neuropathology of older persons without cognitive impairment from two community-based studies

OBJECTIVE

To examine the relation of National Institute on Aging-Reagan (NIA-Reagan) neuropathologic criteria of Alzheimer disease (AD) to level of cognitive function in persons without dementia or mild cognitive impairment (MCI).

METHODS

More than 2,000 persons without dementia participating in the Religious Orders Study or the Memory and Aging Project agreed to annual detailed clinical evaluation and brain donation. The studies had 19 neuropsychological performance tests in common that assessed five cognitive domains, including episodic memory, semantic memory, working memory, perceptual speed, and visuospatial ability. A total of 134 persons without cognitive impairment died and underwent brain autopsy and postmortem assessment for AD pathology using NIA-Reagan neuropathologic criteria for AD, cerebral infarctions, and Lewy bodies. Linear regression was used to examine the relation of AD pathology to level of cognitive function proximate to death.

RESULTS

Two (1.5%) persons met NIA-Reagan criteria for high likelihood AD, and 48 (35.8%) met criteria for intermediate likelihood; 29 (21.6%) had cerebral infarctions, and 18 (13.4%) had Lewy bodies. The mean Mini-Mental State Examination score proximate to death was 28.2 for those meeting high or intermediate likelihood AD by NIA-Reagan criteria and 28.4 for those not meeting criteria. In linear regression models adjusted for age, sex, and education, persons meeting criteria for intermediate or high likelihood AD scored about a quarter standard unit lower on tests of episodic memory (p = 0.01). There were no significant differences in any other cognitive domain.

CONCLUSIONS

Alzheimer disease pathology can be found in the brains of older persons without dementia or mild cognitive impairment and is related to subtle changes in episodic memory.

Parkinsonian signs in subjects with mild cognitive impairment

BACKGROUND

Parkinsonian signs such as gait disturbance, rigidity, bradykinesia, and tremor are common among individuals with dementia and are associated with negative outcomes, but little is known about parkinsonian signs among individuals with mild cognitive impairment (MCI).

OBJECTIVE

To examine the extent to which MCI is associated with parkinsonian signs and the relation between cognitive abilities and parkinsonism among individuals with MCI.

METHODS

Participants included 835 individuals from the Rush Memory and Aging Project, a clinical-pathologic study of common chronic conditions of old age. All participants underwent detailed clinical evaluations which included assessments of parkinsonian signs and cognitive function, and linear regression models were used to examine the associations of MCI and parkinsonism.

RESULTS

In a series of analyses controlled for age, sex, and education, individuals with MCI exhibited significantly more parkinsonism than individuals without cognitive impairment, particularly gait disturbance, bradykinesia, and rigidity. Among individuals with MCI, lower levels of cognitive function, particularly in perceptual speed, were associated with higher levels of parkinsonism; when classified according to MCI subtype, individuals with amnestic vs non-amnestic MCI differed from each other on only one parkinsonian sign, with non-amnestic MCI showing more gait disturbance. Because vascular factors can contribute to cognitive impairment and parkinsonian signs, the authors repeated the core analyses including terms for vascular risk factors and vascular disease and the associations between MCI and parkinsonism persisted.

CONCLUSIONS

Mild cognitive impairment (MCI) is accompanied by parkinsonian signs, which are related to the severity and type of cognitive impairment. The association between MCI and parkinsonism is not explained by vascular risk factors or vascular disease.

Education modifies the association of amyloid but not tangles with cognitive function

The authors quantified amyloid and tau tangles in Religious Orders Study participants. In separate analyses, amyloid and tangles were related to level of cognition. When terms for education's interaction with amyloid and tangles were added, education dampened the association of amyloid with level of cognition (p = 0.02) but not the association of neurofibrillary tangles with level of cognition, suggesting that education is related to factors that reduce the effect of amyloid on cognition.

Mild cognitive impairment is related to Alzheimer disease pathology and cerebral infarctions

OBJECTIVES

To examine the extent to which persons with mild cognitive impairment have intermediate levels of Alzheimer disease (AD) pathology, cerebral infarcts, and Lewy body disease.

METHODS

A total of 180 Catholic clergy participating in the Religious Orders Study underwent annual detailed evaluation and brain autopsy. Blocks of midfrontal, superior temporal, medial temporal lobe, inferior parietal, entorhinal cortex, hippocampus, and substantia nigra were paraffin embedded, and sectioned at 6 mum. Cortical neuritic plaques, diffuse plaques, and neurofibrillary tangles were visualized with Bielschowsky silver stain, and counted and summarized to yield a Braak stage, Consortium to Establish a Registry for Alzheimer's Disease (CERAD) diagnosis, National Institute on Aging (NIA)-Reagan diagnosis, and composite measure of AD pathology. The authors recorded the number and location of all gross chronic cerebral infarctions. Lewy bodies were identified with antibodies to alpha-synuclein. Multiple regression analyses were used to examine the relation of AD pathology and cerebral infarctions to clinical diagnosis proximate to death, controlling for age, sex, and education.

RESULTS

A total of 37 had mild cognitive impairment, 60 did not have cognitive impairment, and 83 had dementia proximate to death. Nearly all persons had at least some AD pathology. Cerebral infarctions were present in 35.2%, and 15.6% had Lewy body disease. Persons with mild cognitive impairment were intermediate in terms of Braak stage and CERAD and NIA-Reagan neuropathologic criteria for AD compared to the other two groups. In multiple regression analyses, persons with mild cognitive impairment had intermediate levels of AD pathology from those without cognitive impairment and those with dementia (test for trend, F = 45.2, p < 0.001). Further, the relation between cognition and AD pathology in persons with mild cognitive impairment did not differ significantly from the relation between cognition and AD pathology in persons with dementia or those without cognitive impairment. Persons with mild cognitive impairment also had intermediate levels of cerebral infarctions (test for trend, p = 0.04). Only 3 (8.1%) persons with mild cognitive impairment had Lewy body disease.

CONCLUSION

These data suggest that mild cognitive impairment may be the earliest clinical manifestation of common age-related neurologic diseases.

Hallucinations, cognitive decline, and death in Alzheimer's disease

The relation of psychotic symptoms to cognitive decline and mortality in Alzheimer's disease (AD) was examined during a mean of 2.2 years in 478 persons selected from clinical settings. Psychotic symptoms were ascertained at baseline and cognition was assessed semiannually with nine tests from which a global measure was formed. In analyses that controlled for age, sex, race, and education, hallucinations (29.6%), especially visual ones, were associated with more rapid global cognitive decline and increased mortality, even after controlling for baseline level of cognition and use of antipsychotic medication, and the association with mortality increased with higher level of education. Delusions and misperceptions were not strongly related to cognitive decline or mortality. The results suggest that hallucinations in Alzheimer's disease, particularly visual ones, are associated with more rapid progression.

Mild cognitive impairment in different functional domains and incident Alzheimer's disease

BACKGROUND

Little is known about factors that predict transition from mild cognitive impairment to Alzheimer's disease (AD).

OBJECTIVE

To examine the relation of impairment in different cognitive systems to risk of developing AD in persons with mild cognitive impairment.

METHODS

Participants are 218 older Catholic clergy members from the Religious Orders Study. At baseline, they met criteria for mild cognitive impairment based on a uniform clinical evaluation that included detailed cognitive testing. Evaluations were repeated annually for up to 10 years. Analyses were controlled for age, sex, and education.

RESULTS

Eighty two persons (37.6%) developed AD. In separate analyses, episodic memory, semantic memory, working memory, and perceptual speed, but not visuospatial ability, were associated with risk of AD, but when analysed together only episodic memory and perceptual speed were associated with AD incidence, with the effect for episodic memory especially strong. Overall, those with impaired episodic memory were more than twice as likely to develop AD as those with impairment in other cognitive domains (relative risk (RR) = 2.45; 95% confidence interval (CI): 1.53 to 3.92), and they experienced more rapid cognitive decline. Lower episodic memory performance was associated with increased risk of AD throughout the observation period, whereas impairment in other cognitive domains was primarily associated with risk during the following year but not thereafter.

CONCLUSION

Among persons with mild cognitive impairment, episodic memory impairment is associated with a substantial and persistent elevation in risk of developing AD compared to impairment in other cognitive systems.

Socioeconomic Characteristics of the Community in Childhood and Cognition in Old Age

We examined the relation of early life socioeconomic circumstances to cognition in older residents of a biracial urban community. Participants had brief cognitive testing three times at approximately 3-year intervals. At baseline, information about early life household and county socioeconomic level was collected. In mixed-effects models adjusted for age, sex, race, and education, both early life household and county socioeconomic levels were positively associated with baseline level of cognition but unrelated to cognitive decline. The results suggest that socioeconomic conditions in early life are associated with level of cognitive function in old age but not with rate of cognitive decline.

Change in body mass index and risk of incident Alzheimer disease

OBJECTIVE

To examine the association of change in body mass index (BMI) with risk of Alzheimer disease (AD).

METHODS

Nine hundred eighteen older Catholic clergy participating in the Religious Orders Study without dementia at baseline were studied. Outcome measures were the clinical diagnosis of AD and change in cognitive function.

RESULTS

During a mean follow-up of 5.5 years, 151 persons developed AD. BMI averaged 27.4 at baseline and declined in about half the participants. In a proportional hazards model adjusted for age, sex, and education, each 1-unit less of BMI at baseline was associated with about a 5% increase in the risk of AD (hazard ratio = 0.944; 95% CI = 0.908 to 0.981), and each 1-unit annual decline in BMI (about the 10th percentile) was associated with about a 35% increase in the risk of AD compared with a person experiencing no change in BMI (about the 50th percentile) (hazard ratio = 0.730; 95% CI = 0.625 to 0.852). The results were similar after controlling for chronic diseases and excluding persons who developed AD during the first 4 years of observation. Random effects models showed that the rate of cognitive decline increased by about 8% for each 1-unit less of BMI at baseline and declined an additional 40%/year in persons losing 1 unit of BMI/year compared with those with no change in BMI.

CONCLUSION

Declining body mass index (BMI) is associated with increased risk of incident Alzheimer disease (AD). Loss of BMI may reflect pathologic processes that contribute to the subsequent development of AD.

Amyloid mediates the association of apolipoprotein E e4 allele to cognitive function in older people

BACKGROUND

The neurobiological changes underlying the association of the apolipoprotein E (APOE) e4 allele with level of cognition are poorly understood.

OBJECTIVE

To test the hypothesis that amyloid load can account for (mediate) the association of the APOE e4 allele with level of cognition assessed proximate to death.

METHODS

There were 44 subjects with clinically diagnosed Alzheimer's disease and 50 without dementia, who had participated in the Religious Orders Study. They underwent determination of APOE allele status, had comprehensive cognitive testing in the last year of life, and brain autopsy at death. The percentage area of cortex occupied by amyloid beta and the density of tau positive neurofibrillary tangles were quantified from six brain regions and averaged to yield summary measures of amyloid load and neurofibrillary tangles. Multiple regression analyses were used to examine whether amyloid load could account for the effect of allele status on level of cognition, controlling for age, sex, and education.

RESULTS

Possession of at least one APOE e4 allele was associated with lower level of cognitive function proximate to death (p = 0.04). The effect of the e4 allele was reduced by nearly 60% and was no longer significant after controlling for the effect of amyloid load, whereas there was a robust inverse association between amyloid and cognition (p = 0.001). Because prior work had suggested that neurofibrillary tangles could account for the association of amyloid on cognition, we next examined whether amyloid could account for the effect of allele status on tangles. In a series of regression analyses, e4 was associated with density of tangles (p = 0.002), but the effect of the e4 allele was reduced by more than 50% and was no longer significant after controlling for the effect of amyloid load.

CONCLUSION

These findings are consistent with a sequence of events whereby the e4 allele works through amyloid deposition and subsequent tangle formation to cause cognitive impairment.

Social resources and cognitive decline in a population of older African Americans and whites

OBJECTIVE

To examine the relation of social resources and cognitive decline in older adults.

METHODS

Data are from the Chicago Health and Aging Project, an epidemiologic study of risk factors for Alzheimer disease (AD) and other common conditions in a geographically defined population of older persons. The sample consisted of 6,102 non-Hispanic African Americans (61.2%) and whites, aged > or = 65, who underwent up to three interviews during an average of 5.3 years of follow-up. Each interview included administration of four cognitive function tests from which a composite measure of cognition was formed. Social networks were based on the number of children, relatives, and friends seen at least once a month. Social engagement was measured with four items related to social and productive activity.

RESULTS

Higher number of social networks and level of social engagement were positively correlated with initial level of cognitive function (networks estimate = 0.003, engagement estimate = 0.060, both p < 0.001). Both resources were also associated with a reduced rate of cognitive decline. A high (90th percentile) number of networks reduced the rate of decline by 39% compared to a low level (10th percentile), and high social engagement reduced decline by 91%. These relations remained after controlling for socioeconomic status, cognitive activity, physical activity, depressive symptoms, and chronic medical conditions.

CONCLUSIONS

Greater social resources, as defined by social networks and social engagement, are associated with reduced cognitive decline in old age.

The apolipoprotein E epsilon4 allele increases the odds of chronic cerebral infarction [corrected] detected at autopsy in older persons

BACKGROUND AND PURPOSE

Studies investigating the relation of the apolipoprotein E (apoE) epsilon4 allele to clinical stroke and to vascular changes on magnetic resonance imaging have been conflicting. Little data are available regarding the relation of apoE epsilon4 to cerebral infarctions documented on postmortem examination.

METHODS

We studied the apoE epsilon4 allele in 214 deceased members of the Religious Orders Study, a longitudinal clinical-pathologic study of aging and Alzheimer disease. The apoE genotype was determined using DNA from lymphocytes. Brains were removed a median of 5 hours (interquartile range, 5.5) after death. At postmortem examination, age, location, and size of macroscopic chronic cerebral infarctions were recorded from 1-cm coronal slabs after paraformaldehyde fixation. We also examined 20-microm paraffin-embedded sections of midfrontal and calcarine cortex for amyloid angiopathy on a scale of 1 to 4.

RESULTS

Subjects included 96 males and 118 females with a mean age at death of 86 years (SD, 7). Sixty-five subjects (30.4%) had at least 1 apoE epsilon4 allele and 76 (35.5%) exhibited cerebral infarctions. More than 74% of the subjects exhibited amyloid angiopathy with a mean score of 1.4+/-1.2. After controlling for age and sex, apoE epsilon4 increased the odds of cerebral infarction by 2.3-fold (95% CI, 1.2 to 4.2). apoE epsilon4 increased the odds of cortical 3.2-fold (95% CI, 1.3 to 7.7) and subcortical infarctions 2.3-fold (95% CI, 1.2 to 4.5). The effect was unchanged after accounting for amyloid angiopathy.

CONCLUSIONS

apoE epsilon4 increases the odds of chronic cerebral infarction detected at autopsy in older persons.

Proneness to psychological distress and risk of Alzheimer disease in a biracial community

Persons without dementia residing in a biracial community completed a brief scale of proneness to psychological distress, and 1,064 were subsequently examined for incident Alzheimer disease (AD) 3 to 6 years later. In analyses controlling for selected demographic and clinical variables, persons prone to distress were 2.4 times more likely to develop AD than persons not distress prone. This effect was substantially stronger in white persons compared to African Americans.

Education and the course of cognitive decline in Alzheimer disease

OBJECTIVE

To test the hypothesis that higher level of education is related to more rapid cognitive decline in Alzheimer disease (AD).

METHODS

Participants are older persons with clinically diagnosed AD recruited from health care facilities in the Chicago area. At 6-month intervals for up to 4 years, they underwent uniform structured clinical evaluations that included administration of nine cognitive performance tests from which a composite measure of global cognition was derived. Analyses are based on 494 persons with follow-up data (89.3% of those eligible). In mixed models that allowed for linear and nonlinear decline, the authors first accounted for the effects of age on cognition and then tested the relation of education to rate of cognitive decline.

RESULTS

Global cognitive decline had linear and nonlinear components, resulting in a gradually accelerating course of decline. Age was related to linear but not nonlinear decline, with more rapid decline observed in younger compared with older persons. Higher educational level was related to more rapid global cognitive decline, as hypothesized, with education related to the nonlinear but not the linear component of decline.

CONCLUSION

Higher educational attainment is associated with a slightly accelerated rate of cognitive decline in Alzheimer disease.

MRI-derived entorhinal volume is a good predictor of conversion from MCI to AD

With high-resolution quantitative magnetic resonance imaging (MRI) techniques, it is possible to examine alterations in brain anatomy in vivo and to identify regions affected in the earliest stages of Alzheimer's disease (AD). In the present study, 27 patients diagnosed with mild cognitive impairment (MCI) received a high-resolution MRI scan at baseline and were followed with yearly clinical evaluations. Ten of the 27 patients converted to AD during a 36-month period following the baseline clinical evaluation. Hippocampal and entorhinal cortex volumes derived from the baseline scan were compared to determine which of these two regions, known to be pathologically involved very early in the course of AD, could best differentiate MCI converters from non-converters. Although both entorhinal and hippocampal volumes were found to be independent predictors of the likelihood of conversion to AD, it was the right hemisphere entorhinal volume that best predicted conversion with a concordance rate of 93.5%.

Diabetes mellitus and progression of rigidity and gait disturbance in older persons

BACKGROUND

Parkinsonian-like signs, including rigidity, gait disturbance, and bradykinesia, are common and progressive in old age and are associated with morbidity and mortality. Few risk factors for these signs have been identified. Diabetes mellitus, also a common chronic condition in old age and known to be associated with physical and neurologic disability, may be associated with parkinsonian-like signs.

OBJECTIVE

To examine the relation of diabetes to four parkinsonian-like signs.

METHODS

Participants were 822 older Catholic clergymen and women who were without clinically diagnosed Parkinson disease or dementia at baseline. For up to 9 years, they had uniform annual evaluations, which included a modified version of the motor portion of the Unified Parkinson's Disease Rating Scale, from which previously established measures of four specific parkinsonian-like signs were derived. Participants were evaluated for the presence of diabetes, based on direct medication inspection and history.

RESULTS

Diabetes was present in 128 (15.6%) participants. In random effects models controlling for age, sex, and education, diabetes was associated with worsening rigidity (p < 0.01) and gait (p < 0.05), over an average of 5.6 years of follow-up, but not with change in bradykinesia or tremor. The presence of stroke did not substantially affect the association of diabetes with rigidity but reduced the association of diabetes with gait to a trend (p = 0.08).

CONCLUSION

Diabetes may be a previously unrecognized risk factor for progression of parkinsonian-like signs in older persons.

Depressive symptoms, clinical AD, and cortical plaques and tangles in older persons

BACKGROUND

Depressive symptoms in old age have been associated with risk of Alzheimer disease (AD), but it is uncertain whether they are an independent risk factor for disease or an early clinical sign of its underlying pathology.

METHODS

A group of 130 older Catholic nuns, priests, and brothers underwent detailed annual clinical evaluations and brain autopsy at death. The evaluations included administration of a modified 10-item Center for Epidemiologic Studies Depression Scale (CES-D) and 19 cognitive performance tests and clinical classification of dementia and AD. On postmortem examination, neuritic plaques, diffuse plaques, and neurofibrillary tangles in tissue samples from four cortical regions were counted, and a previously established composite measure of cortical plaque and tangle density (range 0 to 2.98) was derived. All analyses were adjusted for age, sex, and education.

RESULTS

Participants reported a mean 1.5 depressive symptoms (SD 1.6) on the CES-D scale averaged across evaluations. In a logistic regression model, the odds of clinically diagnosed AD proximate to death increased by 1.33 (95% CI 1.01 to 1.76) for each depressive symptom and by 8.41 (95% CI 3.49 to 20.26) for each unit on the composite measure of pathology. In subsequent analyses, depressive symptoms were not related to level of pathology and did not modify the relation of pathology to clinical AD. In a series of linear regression models that controlled for pathology, depressive symptoms were related to level of cognitive function proximate to death and did not modify the association of pathology with cognition.

CONCLUSION

The association of depressive symptoms with clinical AD and cognitive impairment appears to be independent of cortical plaques and tangles.

Dietary fat intake and 6-year cognitive change in an older biracial community population

OBJECTIVE

To examine whether consumption of different types of fat is associated with age-related change in cognition.

METHODS

The authors related fat consumption to 6-year change in cognitive function among 2,560 participants of the Chicago Health and Aging Project, ages 65 and older, with no history of heart attack, stroke, or diabetes at baseline. Fat intake was measured by food frequency questionnaire. Cognitive function was measured at baseline and 3-year and 6-year follow-ups, using the average z score of four cognitive tests: the East Boston Tests of Immediate and Delayed Recall, the Mini-Mental State Examination, and the Symbol Digit Modalities Test.

RESULTS

In separate mixed models adjusted for demographic and cardiovascular risk factors and intakes of antioxidant nutrients and other dietary fats, higher intakes of saturated fat (p for trend = 0.04) and trans-unsaturated fat (p for trend = 0.07) were linearly associated with greater decline in cognitive score over 6 years. These associations became stronger in analyses that eliminated persons whose fat intake changed in recent years or whose baseline cognitive scores were in the lowest 15%. Inverse associations with cognitive decline were observed in these latter restricted analyses for high intake of monounsaturated fat and a high ratio of polyunsaturated to saturated fat intake. Intakes of total fat, vegetable and animal fats, and cholesterol were not associated with cognitive change.

CONCLUSION

A diet high in saturated or trans-unsaturated fat or low in nonhydrogenated unsaturated fats may be associated with cognitive decline among older persons.

Influence of behavioral symptoms on rates of institutionalization for persons with Alzheimer's disease

BACKGROUND

Recent studies indicate that behavioral symptoms may play a key role in decisions to institutionalize persons with Alzheimer's disease (AD), but the specific types of behavior that contribute to this increased risk have not been reliably identified. The relationship between behavioral symptoms and time to institutionalization was evaluated in a 4-year longitudinal study.

METHOD

A total of 410 persons with the clinical diagnosis of AD completed annual clinical evaluations to assess cognitive impairment, functional limitations, delusions, hallucinations, depressive symptoms and physical aggression. Participation rates among survivors exceeded 90% for four follow-up evaluations with complete ascertainment of mortality and institutionalization. Time to institutionalization was evaluated using proportional hazards regression models in relation to time-varying clinical features.

RESULTS

In multivariate models, adjusted for demographic and social variables, four clinical features emerged as the predominant predictors of institutionalization: cognitive impairment level, physical aggression, hallucinations and depressive symptoms. These associations were virtually unchanged in analyses controlling for mortality.

CONCLUSIONS

Specific behavioral symptoms are important independent risk factors for institutionalization in persons with AD. Because behavioral symptoms are susceptible to therapy, efforts to modify or prevent these symptoms deserve careful consideration as a means to delay institutionalization for persons with this disease.

Dietary niacin and the risk of incident Alzheimer's disease and of cognitive decline

BACKGROUND

Dementia can be caused by severe niacin insufficiency, but it is unknown whether variation in intake of niacin in the usual diet is linked to neurodegenerative decline. We examined whether dietary intake of niacin was associated with incident Alzheimer's disease (AD) and cognitive decline in a large, prospective study.

METHODS

This study was conducted in 1993-2002 in a geographically defined Chicago community of 6158 residents aged 65 years and older. Nutrient intake was determined by food frequency questionnaire. Four cognitive tests were administered to all study participants at 3 year intervals in a 6 year follow up. A total of 3718 participants had dietary data and at least two cognitive assessments for analyses of cognitive change over a median 5.5 years. Clinical evaluations were performed on a stratified random sample of 815 participants initially unaffected by AD, and 131 participants were diagnosed with 4 year incident AD by standardised criteria.

RESULTS

Energy adjusted niacin intake had a protective effect on development of AD and cognitive decline. In a logistic regression model, relative risks (95% confidence intervals) for incident AD from lowest to highest quintiles of total niacin intake were: 1.0 (referent) 0.3 (0.1 to 0.6), 0.3 (0.1 to 0.7), 0.6 (0.3 to 1.3), and 0.3 (0.1 to 0.7) adjusted for age, sex, race, education, and ApoE e4 status. Niacin intake from foods was also inversely associated with AD (p for linear trend = 0.002 in the adjusted model). In an adjusted random effects model, higher food intake of niacin was associated with a slower annual rate of cognitive decline, by 0.019 standardised units (SU) per natural log increase in intake (mg) (p = 0.05). Stronger associations were observed in analyses that excluded participants with a history of cardiovascular disease (beta = 0.028 SU/year; p = 0.008), those with low baseline cognitive scores (beta = 0.023 SU/year; p = 0.02), or those with fewer than 12 years' education (beta = 0.035 SU/year; p = 0.002)

CONCLUSION

Dietary niacin may protect against AD and age related cognitive decline.

Blood pressure and late-life cognitive function change: A biracial longitudinal population study

OBJECTIVE

To examine the relation of blood pressure (BP) to subsequent decline in cognitive function among persons age 65 or over.

METHODS

All persons age 65 or over in a geographically defined community were invited to participate in a longitudinal study of problems of the elderly. Interviews were conducted in the participants' homes and included two BP measures and four tests of cognitive function. Follow-up interviews 3 and 6 years after baseline repeated the cognitive function tests. These analyses included 4,284 individuals who had baseline and at least one follow-up measure of cognitive function. The average of z scores of the individual cognitive function tests was used as a global measure of cognitive function.

RESULTS

In random effects analyses controlling for age, sex, education, and race, there was no significant linear association of either systolic or diastolic BP with 6-year change in global cognitive function score. There was no significant curvilinear association with systolic BP. In tests for a curvilinear association with diastolic BP, there was a suggestion of increased decline among those with low or high diastolic BP (p = 0.03 for the quadratic diastolic term). At baseline, 50% of participants took some type of medication affecting BP.

CONCLUSION

In this community population where BP treatment was common, there was no association of either high systolic or high diastolic BP at the beginning of the observation interval with 6-year cognitive decline.

A population-based longitudinal study of cognitive functioning in the menopausal transition

BACKGROUND

No longitudinal studies have tracked cognitive performance through the menopausal transition and thus the impact of the transition on cognition, independent of aging, is not known. The authors hypothesized that a decline in cognitive functioning occurs as women progress through the menopausal transition, independent of age, educational level, family income, ethnicity, and baseline self-perceived health.

METHOD

The authors began a population-based, longitudinal study in January 1996 with yearly follow-up interviews. This report includes follow-up through November 2001. The authors randomly selected African American and white women from a census of two contiguous Chicago communities. After screening for eligibility (age 42 to 52 years, premenopausal or early perimenopausal, no exogenous hormone use in the past 3 months, and no hysterectomy), 868 agreed to participate. Women who became pregnant, had a hysterectomy, or began using hormones were censored from that time onward. This study reports on 803 women for whom cognitive assessments were available. The authors assessed working memory (Digit Span Backward) and perceptual speed (Symbol Digit Modalities Test).

RESULTS

Contrary to the hypothesis, the authors found small but significant increases over time during the premenopausal and perimenopausal phases. This trend was not accounted for by chronological age, education, family income, ethnicity, or baseline self-perceived health.

CONCLUSIONS

Transition through menopause is not accompanied by a decline in working memory and perceptual speed.

Cognitive activity and cognitive decline in a biracial community population

BACKGROUND

Frequent participation in cognitively stimulating activities has been associated with reduced risk of AD in several prospective studies. However, the association of cognitive activity with cognitive decline, the principal manifestation of AD, is not well understood.

METHODS

More than 4,000 older residents of a geographically defined biracial community of Chicago were interviewed at approximately 3-year intervals for an average of 5.3 years. Each interview included administration of four cognitive function tests from which a previously established global measure was derived. At baseline, each person rated frequency of participation in cognitively stimulating activities (e.g., reading a magazine) from which a previously established composite measure of cognitive activity was derived.

RESULTS

Cognitive activity scores ranged from 1 to 5 (mean = 3.14, SD = 0.66), with higher scores indicating more frequent participation. More frequent cognitive activity was associated with reduced cognitive decline during follow-up. In a model that controlled for baseline level of cognition, age, sex, race, and education, a 1-point increase in cognitive activity score was associated with an approximately 19% decrease in annual rate of cognitive decline (p < 0.001). This effect remained when we controlled for depressive symptoms and chronic medical conditions (p < 0.001), and when we excluded persons with evidence of memory impairment at baseline (p < 0.001).

CONCLUSION

Frequent participation in cognitively stimulating activities is associated with reduced cognitive decline in older persons.

Cerebral infarctions and the likelihood of dementia from Alzheimer disease pathology

BACKGROUND

Alzheimer disease (AD) is the most common cause of dementia. The effect of cerebral infarctions on the likelihood of dementia from AD pathology is not well understood.

METHODS

The study included 153 deceased Catholic clergy who participated in the Religious Orders Study. Annual evaluations, including 19 tests of cognitive function, were performed to determine a diagnosis of dementia and level of cognitive abilities proximate to death. At autopsy, neuritic and diffuse plaques and neurofibrillary tangles were counted and combined into a standardized summary measure of AD pathology. Number, volume, side, and distribution of old macroscopic infarctions were recorded. Analyses included logistic and linear regression, adjusting for age, sex, and education.

RESULTS

The AD pathology score ranged from 0 to 2.93 units, and 54 persons had infarctions. There was no relationship between AD pathology and infarctions (r = 0.04, p = 0.56). Each unit of AD pathology increased the odds of dementia by 4.40-fold (95% CI = 2.33 to 8.32), and this was essentially unchanged after accounting for infarctions. The presence of one or more infarctions independently increased the odds of dementia by 2.80-fold (95% CI = 1.26 to 6.21). There was no interaction between AD pathology and infarctions to further increase the likelihood of dementia (p = 0.39). The number, size, and distribution of infarctions added to the odds of dementia but also did not show an interaction with AD pathology. Similar results were found in analyses with global cognitive function and five different cognitive systems.

CONCLUSION

Cerebral infarctions independently contribute to the likelihood of dementia but do not interact with AD pathology to increase the likelihood of dementia beyond their additive effect.

Multivariate longitudinal models for complex change processes

Longitudinal studies offer us an opportunity to develop detailed descriptions of the process of growth and development or of the course of progression of chronic diseases. Most longitudinal analyses focus on characterizing change over time in a single outcome variable and identifying predictors of growth or decline. Both growth and degenerative diseases, however, are complex processes with multiple markers of change, so that it may be important to model more than one outcome measure and to understand their relationship over time. We consider random effects models for the association between the trajectories of two outcomes over time, and then compare their properties to approaches based on separate ordinary least-squares estimates of change. We then illustrate with an example from the Religious Orders Study, a longitudinal cohort study of more than 900 members of Catholic religious orders who have had up to eight annual clinical examinations.

Premorbid proneness to distress and episodic memory impairment in Alzheimer's disease

BACKGROUND

Chronic stress has been associated with impaired episodic memory, but the association of premorbidly experienced distress with memory function in Alzheimer's disease is unknown.

OBJECTIVE

To investigate the link between proneness to distress and Alzheimer's disease.

METHODS

Participants were 363 persons with clinically diagnosed Alzheimer's disease. At baseline, a knowledgeable informant rated each person's premorbid personality (that is, before dementia onset) along five dimensions, one of which was the tendency to experience psychological distress. Participants underwent structured clinical evaluations at baseline and then annually for up to four years. Each evaluation included 17 cognitive tests from which previously established measures of episodic memory, visuoconstruction, repetition, and naming were derived.

RESULTS

In a series of random effects models adjusted for age, sex, and education, premorbid distress proneness was associated with baseline impairment in episodic memory but not with impairment in other cognitive domains, or with change in any cognitive domain. No other trait was related to baseline function or rate of decline in any cognitive domain.

CONCLUSIONS

The results suggest that premorbid proneness to experience psychological distress is related to level of impairment in episodic memory in persons with Alzheimer's disease, but neither distress proneness nor other personality traits are related to disease progression.

Proneness to psychological distress is associated with risk of Alzheimer's disease

BACKGROUND

Chronic stress is associated with hippocampal damage and impaired memory in animals and humans.

OBJECTIVE

To examine this relationship with clinical and pathologic data from the Religious Orders Study.

METHODS

Older Catholic clergy members underwent annual clinical evaluations, which included clinical classification of Alzheimer's disease (AD) and detailed cognitive function testing from which composite measures of global cognition and specific cognitive functions were derived. At the baseline evaluation, participants completed a measure of the tendency to experience psychological distress, a stable personality trait that served as an indicator of susceptibility to negative emotional states across the life span. More than 90% of participants who died underwent a uniform postmortem examination of the brain from which summary measures of AD pathology were derived. The association of distress proneness with incident AD and cognitive decline and with measures of AD pathology was examined in analyses adjusted for selected demographic and clinical variables.

RESULTS

During a mean of 4.9 years of follow-up, 140 persons developed AD. Those high in distress proneness (90th percentile) had twice the risk of developing AD than those low in distress proneness (10th percentile). Distress proneness was related to decline in episodic memory but not in other cognitive domains, with a >10-fold increase in episodic memory decline in those high in distress proneness compared with those low in the trait. Among those who died, however, distress proneness was not related to common measures of AD pathology.

CONCLUSION

Proneness to experience psychological distress is a risk factor for AD, an effect independent of AD pathologic markers such as cortical plaques and tangles.

Depressive symptoms and cognitive decline in a community population of older persons

BACKGROUND

An association between depressive symptoms and cognitive decline has been observed in selected cohorts of older people, but studies of defined populations have had conflicting results.

OBJECTIVE

To test whether the level of depressive symptoms predicted the rate of cognitive decline in a biracial community of older persons.

METHODS

4392 older people (88% of those eligible) from a defined community in Chicago completed two or three structured interviews at approximately three year intervals for an average of 5.3 years. At the baseline interview, the number of depressive symptoms was assessed with a 10 item version of the Center for Epidemiologic Studies Depression scale. Cognitive function was assessed at each interview with four performance tests, from which a previously established measure of global cognition was derived. Random effects models were used to assess change in cognition and its relation to depressive symptoms, controlling for age, sex, race, education, and baseline cognitive function.

RESULTS

Participants reported a median of one depressive symptom at baseline (interquartile range, 0 to 2). For each depressive symptom, the rate of cognitive decline increased by a mean of about 5%. Results were not substantially changed when persons with cognitive impairment at baseline were excluded, or when chronic illness or participation in cognitively stimulating activities was controlled, and the association was not modified by age, sex, race, or education.

CONCLUSIONS

The results suggest that depressive symptoms predict cognitive decline in old age.

Rate of cognitive decline and mortality in Alzheimer’s disease

Background: Alzheimer’s disease (AD) is associated with increased mortality, but survival in those with the disease varies widely. It is uncertain how much of the variation in survival is due to individual differences in rate of disease progression.

Methods: During a 4-year period, 354 persons with AD underwent annual clinical evaluations that included administration of 17 cognitive function tests, from which global and specific measures of cognitive function were derived. A growth curve approach was used to assess individual rates of cognitive decline and proportional hazards models adjusted for age, sex, and education to examine the associations of baseline level of cognition and rate of cognitive decline with mortality.

Results: During the 4-year study period, 242 persons survived and 112 died. At baseline, the global measure of cognition ranged from −1.68 to 1.36 (mean = 0.03, SD = 0.57), with higher scores indicating better function. Baseline level of cognition was not related to mortality (p = 0.12). Global cognition declined an average of 0.56 unit/year, with substantial heterogeneity (SD = 0.41). To determine mortality risk, persons were divided into quartiles based on rate of cognitive decline and survival contrasted in the quartile with the least decline with survival in each remaining quartile, adjusting for baseline level of cognition. Compared with those with the least decline, risk of death was increased more than threefold in the subgroup with mild decline, more than fivefold in those with moderately rapid decline, and more than eightfold in those with the most rapid decline. Similar results were found after controlling for baseline health and disability and in analyses using specific cognitive function measures.

Conclusion: Mortality in AD is strongly associated with rate of cognitive decline.

Education modifies the relation of AD pathology to level of cognitive function in older persons

OBJECTIVE

To test the hypothesis that years of formal education modifies the relation of AD pathology to level of cognitive function.

METHODS

A total of 130 older Catholic clergy participating in the Religious Orders Study underwent annual cognitive function testing and brain autopsy at the time of death. Individual cognitive function tests were z-scored and averaged to yield a global measure of cognitive function and summary measures of five different cognitive abilities. Neuritic and diffuse plaques and neurofibrillary tangles were counted in separate 1 mm(2) areas of maximal density. Counts were converted to standard scores by dividing by their SD, and combined to yield a global AD pathology score and summary scores of each postmortem index. Linear regression was used to examine the relation of education and AD pathology scores to level of cognitive function proximate to death, controlling for age and sex. Subsequent analyses tested the interaction between education and each AD pathology score to determine whether education modified the relation of AD pathology to level of cognitive function. Additional analyses examined these associations on five specific cognitive abilities.

RESULTS

Both years of formal education (regression coefficient = 0.073, p = 0.0001) and the global AD pathology score (regression coefficient = -0.689, p < 0.0001) were related to level of cognitive function. When an interaction term between education and AD pathology was added to the model, the association between a unit of AD pathology and level of cognitive function was 0.088 (p = 0.0078) standard unit less for each year of education than the level predicted from the model without the interaction term. Whereas neuritic plaques, diffuse plaques, and neurofibrillary tangles were all strongly related to cognitive function, education only modified the relation of neuritic plaques (p = 0.002) and diffuse plaques (p = 0.03) to cognition, but not neurofibrillary tangles. In analyses examining five different cognitive abilities, the interaction between education and the neuritic plaque score was strongest for perceptual speed and weakest for episodic memory.

CONCLUSIONS

These data provide strong evidence that the relation between senile plaques and level of cognitive function differs by years of formal education.

Gender, cognitive decline, and risk of AD in older persons

BACKGROUND

Cross-sectional studies suggest gender differences in cognitive function and risk of AD in older persons. However, longitudinal studies comparing change in cognitive function and risk of AD in men and women have had mixed results. The authors investigated gender differences in rate of decline for different cognitive systems and for risk of developing AD.

METHODS

Participants were from the Religious Orders Study, a longitudinal, clinical-pathologic study of aging and AD in older Catholic nuns, priests, and brothers. Longitudinal data were available from 577 older women and 271 older men, who completed an average of 5.8 annual evaluations with more than 95% follow-up participation in survivors. The evaluations included 21 neuropsychological tests, from which summary measures of global cognitive function and 5 functional domains were formed, and clinical classification of AD.

RESULTS

Random effects models were used to analyze change in cognitive function, and proportional hazards models were used to assess risk of incident AD. On average, men and women declined in all abilities during the 8-year period but did not differ in annual rates of change in analyses that controlled for age, education, and initial level of cognitive function. Risk of incident AD did not differ between men and women. Furthermore, results were unchanged after controlling for possession of the apolipoprotein-epsilon4 allele. Duration of estrogen use was related to rate of global cognitive decline and visuospatial abilities in women but did not influence comparisons between men and women in cognitive decline.

CONCLUSIONS

The results suggest that patterns of cognitive decline and incidence of AD are similar in older men and women.

Terminal decline in cognitive function

BACKGROUND

Impending death is thought to be associated with age-related cognitive decline, but this association has not been well studied.

METHODS

Participants were 763 older Roman Catholic nuns, priests, and brothers without dementia at baseline. They completed an average of 5.6 annual evaluations (range 2 to 9), with >95% follow-up participation in survivors. Each evaluation included administration of 19 cognitive function tests from which previously established measures of global cognition (mean = 0.108, SD = 0.502) and specific cognitive functions were derived. In a series of change point random effects models, the average point before death when rate of cognitive decline changed was identified, and rates of cognitive decline before and after the optimal change point were estimated, controlling for the effects of age, sex, and education.

RESULTS

There were 122 deaths during the observation period. Those who died had lower global cognitive function at baseline than survivors (by 0.103 unit; p = 0.03), and beginning about 43 months before death, their annual rate of global cognitive decline sharply accelerated from an annual loss of 0.026 to 0.173 unit, a more than sixfold increase. Results were comparable in analyses that controlled for baseline health and disability. Terminal cognitive decline was evident in nearly all of those who died, but at highly variable rates. Remarkably little cognitive decline was evident in survivors. Decline in episodic memory, semantic memory, working memory, perceptual speed, and visuospatial ability also greatly increased about 3 to 6 years prior to death.

CONCLUSION

On average, cognitive decline sharply accelerates in the last years of life.

Relation of cerebral infarctions to dementia and cognitive function in older persons

BACKGROUND

Cerebral infarctions are common in older persons but their relationship with dementia and cognitive function remains controversial.

METHODS

Participants were 164 older Catholic nuns, priests, and brothers who underwent annual clinical evaluation and brain autopsy at death. The authors quantified number and volume of old cerebral infarctions on postmortem examination and determined the association with dementia and cognitive function proximate to death. Analyses controlled for age, sex, and education.

RESULTS

A total of 58 (35.4%) subjects had cerebral infarctions: 29 had one infarction and 29 had multiple infarctions. In logistic regression analyses, infarctions increased the odds of dementia twofold (OR 2.12; 95% CI 1.06 to 4.25). The odds of dementia increased by 2.67-fold for multiple infarctions (95% CI 1.08 to 6.61), whereas the odds of dementia with single infarctions increased by 69% (95% CI 0.70 to 4.09). In linear regression analyses, there was a trend for multiple infarctions to be associated with lower global cognitive scores (-0.44 standard units, p = 0.057). Multiple infarctions were related to perceptual speed, visuospatial skills, and working memory, but not to episodic or semantic memory. The authors found similar results with infarction volume. In secondary analyses, only infarctions that were clinically evident during life were associated with dementia and cognitive function.

CONCLUSION

Cerebral infarctions are associated with a twofold increase in odds of dementia. Odds are higher in persons with multiple, large, or clinically evident infarctions. In addition, cerebral infarctions do not affect all cognitive systems equally, showing the strongest association with perceptual speed and the weakest with episodic memory.

Apolipoprotein E epsilon4 allele, AD pathology, and the clinical expression of Alzheimer's disease

OBJECTIVE

To test the hypothesis that the APOE epsilon4 allele is associated with the clinical manifestations of AD through an association with the pathologic hallmarks of disease.

METHODS

Participants were older Catholic nuns, priests, and brothers who agreed to annual neurologic and neuropsychological evaluation for AD and other common neurologic conditions and brain autopsy at the time of death. There were 77 persons without dementia and 51 with probable AD; 38 participants had one or more epsilon4 alleles.

RESULTS

In logistic regression analyses, controlling for age, sex, and education, the epsilon4 allele was strongly associated with the likelihood of clinical AD (odds = 3.46, 95% CI = 1.44 to 8.33). However, controlling for the effect of AD pathology, the association of the epsilon allele with clinical AD was reduced by >50% and was no longer significant (odds = 1.58, 95% CI = 0.56 to 4.43). Similarly, in linear regression analyses, controlling for age, sex, and education, the epsilon4 allele was strongly associated with level of cognitive function proximate to death (regression coefficient = -0.477, p = 0.005). However, after controlling for the effect of AD pathology, the association of the epsilon4 allele with level of cognition was reduced by >80% and was no longer significant (regression coefficient = -0.093). Similar results were found in analyses using separate measures of neuritic plaques, diffuse plaques, and neurofibrillary tangles, and in analyses of five different cognitive systems (episodic memory, semantic memory, working memory, perceptual speed, and visuospatial ability).

CONCLUSIONS

The APOE epsilon4 allele appears to be associated with the clinical manifestations of AD through an association with the pathologic hallmarks of AD rather than another mechanism.

Cognitive activity and incident AD in a population-based sample of older persons

BACKGROUND

Participation in cognitively stimulating activities is hypothesized to be associated with risk of AD, but knowledge about this association is limited.

METHODS

A biracial community in Chicago was censused, persons aged 65 years and older were asked to participate in an interview, and 6,158 of 7,826 (79%) eligible persons did so. As part of the interview, persons rated current frequency of participation in seven cognitive activities (e.g., reading a newspaper) and nine physical activities (e.g., walking for exercise) from which composite measures of cognitive and physical activity frequency were derived. Four years later, 1,249 of those judged free of AD were sampled for a detailed clinical evaluation of incident disease and 842 (74% of those eligible) participated.

RESULTS

The composite measure of cognitive activity ranged from 1.28 to 4.71 (mean 3.30; SD 0.59), with higher scores indicating more frequent activity. A total of 139 persons met National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for AD on clinical evaluation. In a logistic regression model adjusted for age, education, sex, race, and possession of the APOE epsilon4 allele, a one-point increase in cognitive activity score was associated with a 64% reduction in risk of incident AD (OR 0.36; 95% CI 0.20 to 0.65). By contrast, weekly hours of physical activity (mean 3.5; SD 5.1) was not related to disease risk (OR 1.04; 95% CI 0.98 to 1.10). Education was associated with risk of AD and a similar trend was present for occupation, but these effects were substantially reduced when cognitive activity was added to the model.

CONCLUSION

Frequency of participation in cognitively stimulating activities appears to be associated with risk of AD and may partially explain the association of educational and occupational attainment with disease risk.

The apolipoprotein E epsilon 2 allele and decline in episodic memory

OBJECTIVES

The apolipoprotein E (apoE) epsilon 4 allele is related to decline in multiple cognitive domains, especially episodic memory, but the effect of the epsilon 2 allele on change in different forms of cognitive function has been difficult to establish.

METHODS

Participants are from the Religious Orders Study. At baseline, they were at least 65 years old and free of clinical evidence of dementia. For up to eight years, they underwent annual clinical evaluations that included detailed cognitive function assessment from which previously established summary measures of episodic memory, semantic memory, working memory, perceptual speed, and visuospatial ability were derived. Growth curve models were used to assess change in each measure and its relation to apoE genotype, controlling for age, sex, education, and baseline level of cognition. Follow up data were available in 669 persons (98% of those eligible). We treated those with the epsilon 3/3 genotype as the reference group (n=425), which was contrasted with epsilon 2 ( epsilon 2/2, epsilon 2/3; n=86), and epsilon 4 ( epsilon 3/4, epsilon 4/4; n=158) subgroups.

RESULTS

Rate of episodic memory change in the three subgroups significantly differed, with an average annual increase of 0.016 units in the epsilon 2 subgroup and annual decreases of 0.022 units in those with epsilon 3/3 and of 0.073 units in the epsilon 4 subgroup. The epsilon 2 subgroup did not differ from those with epsilon 3/3 in rate of decline in other cognitive systems. The epsilon 4 subgroup declined more rapidly than those with epsilon 3/3 in semantic memory and perceptual speed but not in working memory or visuospatial ability.

CONCLUSION

Possession of one or more apoE epsilon 2 alleles is associated with reduced decline in episodic memory in older persons.