Long-lasting memory of jasmonic acid-dependent immunity requires DNA demethylation and ARGONAUTE1

Stress can have long-lasting impacts on plants. Here we report the long-term effects of the stress hormone jasmonic acid (JA) on the defence phenotype, transcriptome and DNA methylome of Arabidopsis. Three weeks after transient JA signalling, 5-week-old plants retained induced resistance (IR) against herbivory but showed increased susceptibility to pathogens. Transcriptome analysis revealed long-term priming and/or upregulation of JA-dependent defence genes but repression of ethylene- and salicylic acid-dependent genes. Long-term JA-IR was associated with shifts in glucosinolate composition and required MYC2/3/4 transcription factors, RNA-directed DNA methylation, the DNA demethylase ROS1 and the small RNA (sRNA)-binding protein AGO1. Although methylome analysis did not reveal consistent changes in DNA methylation near MYC2/3/4-controlled genes, JA-treated plants were specifically enriched with hypomethylated ATREP2 transposable elements (TEs). Epigenomic characterization of mutants and transgenic lines revealed that ATREP2 TEs are regulated by RdDM and ROS1 and produce 21 nt sRNAs that bind to nuclear AGO1. Since ATREP2 TEs are enriched with sequences from IR-related defence genes, our results suggest that AGO1-associated sRNAs from hypomethylated ATREP2 TEs trans-regulate long-lasting memory of JA-dependent immunity.

Straight to test reduces time to investigation and treatment

Straight to test (STT) is a recognised pathway for improving the waiting time for red flag referrals. Electronic patient care records (ECR) provide clinicians with a greater volume of clinical information allowing virtual triage and STT. We aimed to assess if using ECR and STT can reduce delays in diagnosis and treatment. A review of 300 colorectal referrals between 2018-2019 was performed. Patients awaiting an appointment were reviewed electronically, by a single colorectal surgeon and re-triaged STT if appropriate. The delay in time from referral to initial review was removed, creating a second group for statistical comparison to demonstrate time saved if the strategy was adopted at the point of original triage. 91.3% (n= 274) were red flag referrals. 94% (n=282) were sent STT. Patients processed via traditional referral and clinic had a median time to scope of 36 days compared with 22.5 days, p < 0.001 if triaged STT via virtual clinic. Median time to management was 59 days for traditional and 35 days for STT, p < 0.001.

Dietary Allergy and Specific IgE in Ulcerative Colitis

Previous authors have considered that allergy to certain foodstuffs may play an important role in the aetiology of ulcerative colitis, but immunological evidence for dietary allergy in ulcerative colitis is inconclusive. A study is reported of 22 patients with ulcerative colitis, with matched controls, in whom total serum IgE and specific IgE to certain foodstuffs have been estimated by the Phadebas PRIST and RAST (Pharmacia) techniques. Allergens tested were egg-white, milk, wheat, rye, oat, fish (cod) and peanut. There was no significant difference in the total serum IgE levels and the food specific IgE activity between the two groups.

Using step width to compare locomotor biomechanics between extinct, non-avian theropod dinosaurs and modern obligate bipeds

How extinct, non-avian theropod dinosaurs locomoted is a subject of considerable interest, as is the manner in which it evolved on the line leading to birds. Fossil footprints provide the most direct evidence for answering these questions. In this study, step width-the mediolateral (transverse) distance between successive footfalls-was investigated with respect to speed (stride length) in non-avian theropod trackways of Late Triassic age. Comparable kinematic data were also collected for humans and 11 species of ground-dwelling birds. Permutation tests of the slope on a plot of step width against stride length showed that step width decreased continuously with increasing speed in the extinct theropods (p < 0.001), as well as the five tallest bird species studied (p < 0.01). Humans, by contrast, showed an abrupt decrease in step width at the walk-run transition. In the modern bipeds, these patterns reflect the use of either a discontinuous locomotor repertoire, characterized by distinct gaits (humans), or a continuous locomotor repertoire, where walking smoothly transitions into running (birds). The non-avian theropods are consequently inferred to have had a continuous locomotor repertoire, possibly including grounded running. Thus, features that characterize avian terrestrial locomotion had begun to evolve early in theropod history.

Reframing climate change assessments around risk: recommendations for the US National Climate Assessment

Climate change is a risk management challenge for society, with uncertain but potentially severe outcomes affecting natural and human systems, across generations. Managing climate-related risks will be more difficult without a base of knowledge and practice aimed at identifying and evaluating specific risks, and their likelihood and consequences, as well as potential actions to promote resilience in the face of these risks. We suggest three improvements to the process of conducting climate change assessments to better characterize risk and inform risk management actions.

Whale's tail technique: A case series

The Whale's tail technique performed to obtain maximum interdental papilla fill in the anterior region after placement of bone grafts. This study aims to assess the clinical efficacy of this new technique. This report describes a series of three cases with a probing depth of 6–7 mm in the maxillary anterior teeth and their treatment with Whale's tail technique to obtain regeneration and maximum papilla preservation. The cases in this report showed a pocket depth reduction of 3-4mm and a clinical attachment gain of 3-4mm. The application of the “Whale's tail” flap leads to clinically significant improvement of hard and soft tissue conditions and allows regeneration of wide intrabony defects involving the maxillary anterior teeth with notable interdental diastemas, maintaining interproximal tissue to recreate a functional attachment with esthetic results.

Balancing Biomechanical Constraints: Optimal Escape Speeds When There Is a Trade-off between Speed and Maneuverability

The ability for prey to escape a pursuing predator is dependent both on the prey's speed away from the threat and on their ability to rapidly change directions, or maneuverability. Given that the biomechanical trade-off between speed and maneuverability limits the simultaneous maximization of both performance traits, animals should not select their fastest possible speeds when running away from a pursuing predator but rather a speed that maximizes the probability of successful escape. We explored how variation in the relationship between speed and maneuverability-or the shape of the trade-off-affects the optimal choice of speed for escaping predators. We used tablet-based games that simulated interactions between predators and prey (human subjects acting as predators attempting to capture "prey" moving across a screen). By defining a specific relationship between speed and maneuverability, we could test the survival of each of the possible behavioral choices available to this phenotype, i.e., the best combination of speed and maneuverability for prey fitness, based on their ability to escape. We found that the shape of the trade-off function affected the prey's optimal speed for success in escaping, the prey's maximum performance in escaping, and the breadth of speeds over which the prey's performance was high. The optimal speed for escape varied only when the trade-off between speed and maneuverability was non-linear. Phenotypes possessing trade-off functions for which maneuverability was only compromised at high speeds exhibited lower optimal speeds. Phenotypes that exhibited greater increases in maneuverability for any decrease in speed were more likely to have broader ranges of performance, meaning that individuals could attain their maximum performance across a broader range of speeds. We also found that there was a differential response of the subject's learning to these different components of locomotion. With increased experience through repeated trials, subjects were able to successfully catch faster and faster dots. However, no improvement was observed in the subject's ability to capture more maneuverable prey. Our work highlights the costs of high-speed movement on other traits, including maneuverability, which make the use of an animal's fastest speeds unlikely, even when attempting to escape predators. By investigating the shape of the trade-off functions between speed and maneuverability and the way the environment and morphology mediates this trade-off, we can begin to understand why animals choose to move at the speeds they do when they are running away from predators or attempting to capture prey.

Twins and Chronogenetics: Correlated Pathways of Development

The study of developmental processes in twins furnishes a powerful resource for examining the role of gene-action systems in guiding the course of growth [2,9].

While there is a steady and rapid progression from birth onward, the growth rate is not entirely uniform for a given child, but rather moves in episodes of acceleration and lag. The timing of the growth spurts follows a distinctive pattern for each child, and consequently a child who may be smaller than average at one age may then enter a phase of rapid growth, and ultimately catch up with or surpass his peers at a later age.

The effect of such individualized patterns of growth is that many children may change in relative size from one age to the next; and in this sense it may appear that the underlying developmental processes are erratic, rather than coherent. But if there is an underlying ground plan, a chronogenetic pattern, then the distinctive developmental gradients should unfold in synchrony for twins sharing the same genetic make-up. Episodes of acceleration and lag in growth would then occur in parallel for both twins and would presumably represent the activity of timed gene-action systems, which switch on and off according to a predetermined plan.

Genotype patterns at PICALM, CR1, BIN1, CLU, and APOE genes are associated with episodic memory

OBJECTIVE

Several genome-wide association studies (GWAS) have associated variants in late-onset Alzheimer disease (LOAD) susceptibility genes; however, these single nucleotide polymorphisms (SNPs) have very modest effects, suggesting that single SNP approaches may be inadequate to identify genetic risks. An alternative approach is the use of multilocus genotype patterns (MLGPs) that combine SNPs at different susceptibility genes.

METHODS

Using data from 1,365 subjects in the National Institute on Aging Late-Onset Alzheimer's Disease Family Study, we conducted a family-based association study in which we tabulated MLGPs for SNPs at CR1, BIN1, CLU, PICALM, and APOE. We used generalized estimating equations to model episodic memory as the dependent endophenotype of LOAD and the MLGPs as predictors while adjusting for sex, age, and education.

RESULTS

Several genotype patterns influenced episodic memory performance. A pattern that included PICALM and CLU was the strongest genotypic profile for lower memory performance (β = -0.32, SE = 0.19, p = 0.021). The effect was stronger after addition of APOE (p = 0.016). Two additional patterns involving PICALM, CR1, and APOE and another pattern involving PICALM, BIN1, and APOE were also associated with significantly poorer memory performance (β = -0.44, SE = 0.09, p = 0.009 and β = -0.29, SE = 0.07, p = 0.012) even after exclusion of patients with LOAD. We also identified genotype pattern involving variants in PICALM, CLU, and APOE as a predictor of better memory performance (β = 0.26, SE = 0.10, p = 0.010).

CONCLUSIONS

MLGPs provide an alternative analytical approach to predict an individual's genetic risk for episodic memory performance, a surrogate indicator of LOAD. Identifying genotypic patterns contributing to the decline of an individual's cognitive performance may be a critical step along the road to preclinical detection of Alzheimer disease.

Total daily physical activity and the risk of AD and cognitive decline in older adults

OBJECTIVE

Studies examining the link between objective measures of total daily physical activity and incident Alzheimer disease (AD) are lacking. We tested the hypothesis that an objective measure of total daily physical activity predicts incident AD and cognitive decline.

METHODS

Total daily exercise and nonexercise physical activity was measured continuously for up to 10 days with actigraphy (Actical®; Philips Healthcare, Bend, OR) from 716 older individuals without dementia participating in the Rush Memory and Aging Project, a prospective, observational cohort study. All participants underwent structured annual clinical examination including a battery of 19 cognitive tests.

RESULTS

During an average follow-up of about 4 years, 71 subjects developed clinical AD. In a Cox proportional hazards model adjusting for age, sex, and education, total daily physical activity was associated with incident AD (hazard ratio = 0.477; 95% confidence interval 0.273-0.832). The association remained after adjusting for self-report physical, social, and cognitive activities, as well as current level of motor function, depressive symptoms, chronic health conditions, and APOE allele status. In a linear mixed-effect model, the level of total daily physical activity was associated with the rate of global cognitive decline (estimate 0.033, SE 0.012, p = 0.007).

CONCLUSIONS

A higher level of total daily physical activity is associated with a reduced risk of AD.

Terminal dedifferentiation of cognitive abilities

OBJECTIVE

To test the cognitive dedifferentiation hypothesis that cognitive abilities become increasingly correlated in late life.

METHODS

Participants are 174 older persons without dementia at the beginning of a longitudinal clinical-pathologic cohort study. At annual intervals for 6 to 15 years prior to death, they completed a battery of cognitive performance tests from which previously established composite measures of episodic memory, semantic memory, working memory, and perceptual speed were derived. At death, there was a uniform neuropathologic assessment and levels of diffuse plaques, neuritic plaques, and neurofibrillary tangles were summarized in a composite measure. Change in the 4 cognitive outcomes was analyzed simultaneously in a mixed-effects model that allowed rate of decline to accelerate at a variable point before death.

RESULTS

On average, cognitive decline before the terminal period was relatively gradual, and rates of change in different cognitive domains were moderately correlated, ranging from 0.25 (episodic memory-working memory) to 0.46 (episodic memory-semantic memory). By contrast, cognition declined rapidly during the terminal period, and rates of change in different cognitive functions were strongly correlated, ranging from 0.83 (working memory-perceptual speed) to 0.89 (episodic memory-semantic memory, semantic memory-working memory). Higher level of plaques and tangles on postmortem examination was associated with faster preterminal decline and earlier onset of terminal decline but not with rate of terminal decline or correlations between rates of change in different cognitive functions.

CONCLUSION

In the last years of life, covariation among cognitive abilities sharply increases consistent with the cognitive dedifferentiation hypothesis.

A randomized clinical trial of anticaries therapies targeted according to risk assessment (caries management by risk assessment)

This randomized parallel group clinical trial assessed whether combined antibacterial and fluoride therapy benefits the balance between caries pathological and protective factors. Eligible, enrolled adults (n = 231), with 1-7 baseline cavitated teeth, attending a dental school clinic were randomly assigned to a control or intervention group. Salivary mutans streptococci (MS), lactobacilli (LB), fluoride (F) level, and resulting caries risk status (low or high) assays were determined at baseline and every 6 months. After baseline, all cavitated teeth were restored. An examiner masked to group conducted caries exams at baseline and 2 years after completing restorations. The intervention group used fluoride dentifrice (1,100 ppm F as NaF), 0.12% chlorhexidine gluconate rinse based upon bacterial challenge (MS and LB), and 0.05% NaF rinse based upon salivary F. For the primary outcome, mean caries increment, no statistically significant difference was observed (24% difference between control and intervention groups, p = 0.101). However, the supplemental adjusted zero-inflated Poisson caries increment (change in DMFS) model showed the intervention group had a statistically significantly 24% lower mean than the control group (p = 0.020). Overall, caries risk reduced significantly in intervention versus control over 2 years (baseline adjusted generalized linear mixed models odds ratio, aOR = 3.45; 95% CI: 1.67, 7.13). Change in MS bacterial challenge differed significantly between groups (aOR = 6.70; 95% CI: 2.96, 15.13) but not for LB or F. Targeted antibacterial and fluoride therapy based on salivary microbial and fluoride levels favorably altered the balance between pathological and protective caries risk factors.

Cognitive decline after hospitalization in a community population of older persons

OBJECTIVE

To test the hypothesis that hospitalization in old age is associated with subsequent cognitive decline.

METHODS

As part of a longitudinal population-based cohort study, 1,870 older residents of an urban community were interviewed at 3-year intervals for up to 12 years. The interview included a set of brief cognitive tests from which measures of global cognition, episodic memory, and executive function were derived. Information about hospitalization during the observation period was obtained from Medicare records.

RESULTS

During a mean of 9.3 years, 1,335 of 1,870 persons (71.4%) were hospitalized at least once. In a mixed-effects model adjusted for age, sex, race, and education, the global cognitive score declined a mean of 0.031 unit per year before the first hospitalization compared with 0.075 unit per year thereafter, a more than 2.4-fold increase. The posthospital acceleration in cognitive decline was also evident on measures of episodic memory (3.3-fold increase) and executive function (1.7-fold increase). The rate of cognitive decline after hospitalization was not related to the level of cognitive function at study entry (r = 0.01, p = 0.88) but was moderately correlated with rate of cognitive decline before hospitalization (r = 0.55, p = 0.021). More severe illness, longer hospital stay, and older age were each associated with faster cognitive decline after hospitalization but did not eliminate the effect of hospitalization.

CONCLUSION

In old age, cognitive functioning tends to decline substantially after hospitalization even after controlling for illness severity and prehospital cognitive decline.

Plasma biomarkers of depressive symptoms in older adults

The pathophysiology of negative affect states in older adults is complex, and a host of central nervous system and peripheral systemic mechanisms may play primary or contributing roles. We conducted an unbiased analysis of 146 plasma analytes in a multiplex biochemical biomarker study in relation to number of depressive symptoms endorsed by 566 participants in the Alzheimer's Disease Neuroimaging Initiative (ADNI) at their baseline and 1-year assessments. Analytes that were most highly associated with depressive symptoms included hepatocyte growth factor, insulin polypeptides, pregnancy-associated plasma protein-A and vascular endothelial growth factor. Separate regression models assessed contributions of past history of psychiatric illness, antidepressant or other psychotropic medicine, apolipoprotein E genotype, body mass index, serum glucose and cerebrospinal fluid (CSF) τ and amyloid levels, and none of these values significantly attenuated the main effects of the candidate analyte levels for depressive symptoms score. Ensemble machine learning with Random Forests found good accuracy (~80%) in classifying groups with and without depressive symptoms. These data begin to identify biochemical biomarkers of depressive symptoms in older adults that may be useful in investigations of pathophysiological mechanisms of depression in aging and neurodegenerative dementias and as targets of novel treatment approaches.

Vitamin B12, cognition, and brain MRI measures: a cross-sectional examination

OBJECTIVE

To investigate the interrelations of serum vitamin B12 markers with brain volumes, cerebral infarcts, and performance in different cognitive domains in a biracial population sample cross-sectionally.

METHODS

In 121 community-dwelling participants of the Chicago Health and Aging Project, serum markers of vitamin B12 status were related to summary measures of neuropsychological tests of 5 cognitive domains and brain MRI measures obtained on average 4.6 years later among 121 older adults.

RESULTS

Concentrations of all vitamin B12-related markers, but not serum vitamin B12 itself, were associated with global cognitive function and with total brain volume. Methylmalonate levels were associated with poorer episodic memory and perceptual speed, and cystathionine and 2-methylcitrate with poorer episodic and semantic memory. Homocysteine concentrations were associated with decreased total brain volume. The homocysteine-global cognition effect was modified and no longer statistically significant with adjustment for white matter volume or cerebral infarcts. The methylmalonate-global cognition effect was modified and no longer significant with adjustment for total brain volume.

CONCLUSIONS

Methylmalonate, a specific marker of B12 deficiency, may affect cognition by reducing total brain volume whereas the effect of homocysteine (nonspecific to vitamin B12 deficiency) on cognitive performance may be mediated through increased white matter hyperintensity and cerebral infarcts. Vitamin B12 status may affect the brain through multiple mechanisms.

The relationship between lay and technical views of Escherichia coli O157 risk

Here, we bring together and contrast lay (accessible primarily through social science methodologies) and technical (via risk assessment and epidemiological techniques) views of the risk associated with the Escherichia coli O157 pathogen using two case study areas in the Grampian region of Scotland, and North Wales. Epidemiological risk factors of contact with farm animals, visiting farms or farm fields and having a private water supply were associated with postcode districts of higher than average disease incidence in the human population. However, this was not the case for the epidemiological risk factor of consumption of beef burgers, which was independent of disease incidence in the postcode district of residence. The proportion of the population expressing a high knowledge of E. coli O157 was greatest in high-incidence disease districts compared with low-incidence areas (17% cf. 7%). This supports the hypothesis that in high-disease-incidence areas, residents are regularly exposed to information about the disease through local cases, the media, local social networks, etc. or perhaps that individuals are more likely to be motivated to find out about it. However, no statistically significant difference was found between high- and low-incidence postcode districts in terms of the proportion of the population expressing a high likelihood of personal risk of infection (10% cf. 14%), giving a counterintuitive difference between the technical (epidemiological and quantitative microbiological risk assessment (QMRA)) and the lay assessment of E. coli O157 risk. This suggests that lay evaluations of E. coli O157 risk reflect intuitive and experience-based estimates of the risk rather than probabilistic estimates. A generally strong correspondence was found in terms of the rank order given to potential infection pathways, with environment and foodborne infection routes dominating when comparing public understanding with technical modelling results. Two general conclusions follow from the work. First, that integrative research incorporating both lay and technical views of risk is required in order that informed decisions can be made to handle or treat the risk by the groups concerned (e.g. the public, policy makers/risk managers, etc.). Second, when communicating risk, for example, through education programmes, it is important that this process is two-way with risk managers (e.g. including Food Standards Agency officials and communications team, public health infection control and environmental health officers) both sharing information with the public and stakeholder groups, as well as incorporating public knowledge, values and context (e.g. geographical location) into risk-management decisions.

Hemoglobin level in older persons and incident Alzheimer disease: prospective cohort analysis

OBJECTIVE

To test the hypothesis that level of hemoglobin is associated with incident Alzheimer disease (AD).

METHODS

A total of 881 community-dwelling older persons participating in the Rush Memory and Aging Project without dementia and a measure of hemoglobin level underwent annual cognitive assessments and clinical evaluations for AD.

RESULTS

During an average of 3.3 years of follow-up, 113 persons developed AD. In a Cox proportional hazards model adjusted for age, sex, and education, there was a nonlinear relationship between baseline level of hemoglobin such that higher and lower levels of hemoglobin were associated with AD risk (hazard ratio [HR] for the quadratic of hemoglobin 1.06, 95% confidence interval [CI] 1.01-1.11). Findings were unchanged after controlling for multiple covariates. When compared to participants with clinically normal hemoglobin (n = 717), participants with anemia (n = 154) had a 60% increased hazard for developing AD (95% CI 1.02-2.52), as did participants with clinically high hemoglobin (n = 10, HR 3.39, 95% CI 1.25-9.20). Linear mixed-effects models showed that lower and higher hemoglobin levels were associated with a greater rate of global cognitive decline (parameter estimate for quadratic of hemoglobin = -0.008, SE -0.002, p < 0.001). Compared to participants with clinically normal hemoglobin, participants with anemia had a -0.061 z score unit annual decline in global cognitive function (SE 0.012, p < 0.001), as did participants with clinically high hemoglobin (-0.090 unit/year, SE 0.038, p = 0.018).

CONCLUSIONS

In older persons without dementia, both lower and higher hemoglobin levels are associated with an increased hazard for developing AD and more rapid cognitive decline.

Quantitative genetic variation for thermal performance curves within and among natural populations of Drosophila serrata

Thermal performance curves (TPCs) provide a powerful framework for studying the evolution of continuous reaction norms and for testing hypotheses of thermal adaptation. Although featured heavily in comparative studies, the framework has been comparatively underutilized for quantitative genetic tests of thermal adaptation. We assayed the distribution of genetic (co)variance for TPC (locomotor activity) within and among three natural populations of Drosophila serrata and performed replicated tests of two hypotheses of thermal adaptation--that 'hotter is better' and that a generalist-specialist trade-off underpins the evolution of thermal sensitivity. We detected significant genetic variance within, and divergence among, populations. The 'hotter is better' hypothesis was not supported as the genetic correlations between optimal temperature (T(opt)) and maximum performance (z(max)) were consistently negative. A pattern of variation consistent with a generalist-specialist trade-off was detected within populations and divergence among populations indicated that performance curves were narrower and had higher optimal temperatures in the warmer, but less variable tropical population.

Change in risk of Alzheimer disease over time

OBJECTIVE

To assess whether the risk of incidence of Alzheimer disease (AD) varies over time. The increase in numbers of people at the oldest ages in the population will bring an increase in the number of people with AD. Projections of the size of the increase assume the risk of AD is constant.

METHODS

All persons age 65 or older in a biracial, geographically defined area were invited to participate in a home interview every 3 years. From the approximately 10,000 participants, stratified random samples were selected for detailed clinical evaluation. At each cycle, individuals determined free of AD in a previous cycle, either by examination or by high score on cognitive function tests, were sampled in the subsequent cycle for evaluation for incident AD. The evaluations for disease were structured and uniform across time. These analyses include 1,695 subjects evaluated for incident disease from 1997 through 2008.

RESULTS

AD developed in 360 participants. Change over time in risk of incident disease was assessed in logistic regression analyses including evaluation date and controlling for age, gender, education, race, interval from disease-free designation to evaluation for incident disease, and sample design. The time variable (in years) was not significant (odds ratio = 0.970, 95% confidence interval = 0.902 to 1.044).

CONCLUSIONS

The null relation of evaluation date to disease incidence suggests no recent change in risk of AD over time, and supports this assumption for projections of AD.

Neurodegenerative basis of age-related cognitive decline

OBJECTIVE

To assess the contribution of dementia-related neuropathologic lesions to age-related and disease-related change in cognitive function.

METHODS

A total of 354 Catholic nuns, priests, and brothers had annual clinical evaluations for up to 13 years, died, and underwent brain autopsy. The clinical evaluations included detailed testing of cognitive function from which previously established composite measures of global cognition and specific cognitive functions were derived. As part of a uniform neuropathologic evaluation, the density of neurofibrillary tangles was summarized in a composite measure and the presence of Lewy bodies and gross and microscopic cerebral infarction was noted.

RESULTS

During follow-up, rate of global cognitive decline was gradual at first and then more than quadrupled in the last 4 to 5 years of life consistent with the onset of progressive dementia. Neurofibrillary tangles, cerebral infarction, and neocortical Lewy bodies all contributed to gradual age-related cognitive decline and little age-related decline was evident in the absence of these lesions. Neurofibrillary tangles and neocortical Lewy bodies contributed to precipitous disease-related cognitive decline, but substantial disease-related decline was evident even in the absence of these lesions.

CONCLUSION

Mild age-related decline in cognitive function is mainly due to the neuropathologic lesions traditionally associated with dementia.

Cognitive activity and the cognitive morbidity of Alzheimer disease

OBJECTIVE

To test the hypothesis that frequent cognitive activity predicts slower cognitive decline before dementia onset in Alzheimer disease (AD) and faster decline thereafter.

METHODS

As part of a longitudinal cohort study, older residents of a geographically defined population were assessed at 3-year intervals with brief cognitive performance tests from which a composite measure of global cognition was derived. After each wave of testing, a subset was sampled for clinical evaluation. The present analyses are based on 1,157 participants. They were free of dementia at study enrollment at which time they rated frequency of participation in common cognitively stimulating activities from which a previously validated summary measure was derived. They were sampled for clinical evaluation a mean of 5.6 years after enrollment and subsequently followed a mean of 5.7 years with brief cognitive performance testing at 3-year intervals.

RESULTS

On clinical evaluation, 614 people had no cognitive impairment, 395 had mild cognitive impairment, and 148 had AD. During follow-up, the annual rate of global cognitive decline in persons without cognitive impairment was reduced by 52% (estimate = 0.029, SE = 0.010, p = 0.003) for each additional point on the cognitive activity scale. In the mild cognitive impairment group, cognitive decline rate was unrelated to cognitive activity (estimate = -0.019, SE = 0.018, p = 0.300). In AD, the mean rate of decline per year increased by 42% (estimate = 0.075, SE = 0.021, p < 0.001) for each point on the cognitive activity scale.

CONCLUSION

Mentally stimulating activity in old age appears to compress the cognitive morbidity associated with AD by slowing cognitive decline before dementia onset and hastening it thereafter.

Temporal course of depressive symptoms during the development of Alzheimer disease

OBJECTIVE

To characterize change in depressive symptoms before and after the onset of dementia in Alzheimer disease (AD).

METHOD

We used data from the Chicago Health and Aging Project, a longitudinal cohort study of risk factors for AD in a geographically defined population of old people. Two subsets were analyzed. In 357 individuals who developed incident AD during the study, self-report of depressive symptoms (Center for Epidemiologic Studies Depression Scale) was obtained at 3-year intervals for a mean of 8 to 9 years. In 340 individuals who agreed to annual data collection, informant report of depressive symptoms (Hamilton Depression Rating Scale) was obtained for a mean of 3 years after a diagnosis of AD (n = 107), mild cognitive impairment (n = 81), or no cognitive impairment (n = 152).

RESULTS

The incident AD group reported a barely perceptible increase in depressive symptoms during 6 to 7 years of observation before the diagnosis (0.04 symptoms per year) and no change during 2 to 3 years of observation after the diagnosis except for a slight decrease in positive affect. In those with annual follow-up, neither AD nor its precursor, mild cognitive impairment, was associated with change in informant report of depressive symptoms during a mean of 3 years of observation.

CONCLUSION

Depressive symptoms show little change during the development and progression of AD to a moderate level of dementia severity.

Cognitive decline in incident Alzheimer disease in a community population

OBJECTIVE

To measure the cognitive consequences of incident Alzheimer disease (AD) in older African American and white subjects.

METHODS

Data are from the Chicago Health and Aging Project, a longitudinal cohort study of older white and black persons residing in a geographically defined community. At 3-year intervals, the entire study population completed 4 brief cognitive tests, from which a previously established composite measure of global cognition was derived, and a subset underwent detailed clinical evaluation that supported clinical classification of mild cognitive impairment, dementia, and AD. We used mixed-effects models to examine change in cognitive function following the diagnostic evaluation.

RESULTS

On clinical evaluation, 614 persons were found to have no cognitive impairment, 395 had mild cognitive impairment, and 149 had AD (88.5% mild); 10 persons with other dementias were excluded from analyses. During up to 11 years of observation following the clinical evaluation (mean = 5.5, SD = 2.5), the composite measure of global cognition declined a mean of 0.042 unit per year (SE = 0.008, p < 0.001) in those with no cognitive impairment. In comparison to the no cognitive impairment group, the annual rate of decline was increased more than twofold in mild cognitive impairment (estimate = 0.086, SE = 0.011, p < 0.001) and more than fourfold in AD (estimate = 0.173, SE = 0.020, p < 0.001). Results did not reliably vary by race, sex, or age.

CONCLUSIONS

Alzheimer disease has a devastating impact on cognition, even in its prodromal stages, with comparable effects in African American and white persons.

Insulin-like growth factor receptor 1 (IGF1R) expression and survival in surgically resected non-small-cell lung cancer (NSCLC) patients

BACKGROUND

The purpose of this study is to investigate the prognostic role of insulin-like growth factor receptor 1 (IGF1R) expression in surgically resected non-small-cell lung cancer (NSCLC). Patient characteristics and methods: This retrospective study was conducted in 369 stage I-II-IIIA, surgically resected, NSCLC patients. Patients exposed to anti-epidermal growth factor receptor (EGFR) agents were excluded. IGF1R expression was evaluated by immunohistochemistry in tissue microarray sections.

RESULTS

A positive IGF1R expression (score > or = 100) was observed in 282 cases (76.4%) and was significantly associated with squamous cell histology (P = 0.04) and with grade III differentiation (P = 0.02). No difference in survival was observed between the positive and negative group when score 100 was used as cut-off for discriminating a positive versus a negative IGF1R result (52 versus 48 months, P = 0.99) or when median value of IGF1R expression was used (45 versus 55 months, P = 0.36). No difference in survival was observed between IGF1R-positive and -negative patients in a subgroup of stage I-II adenocarcinoma (n = 137) with known EGFR mutation and copy number status.

CONCLUSIONS

IGF1R expression does not represent a prognostic factor in resected NSCLC patients. Patients with squamous cell carcinoma overexpress IGF1R more frequently than patients with nonsquamous histology, justifying the different sensitivity to anti-IGF1R agents observed in clinical trials.

Coupled Nanomechanical and Raman Microspectroscopic Investigation of Human Third Molar DEJ

The dentino-enamel junction (DEJ) connects enamel, that covers the outer surface of a tooth, to a thicker underlying dentin. The DEJ is a critical interface that permits joining these materials that have widely dissimilar mechanical properties. AFM-based nanoindentation and Raman microspectroscopy were used to define the width and composition of human molar DEJ. Indentation elastic modulus and hardness of enamel, dentin, and DEJ were determined along lines of indents made at 2 μm intervals across the DEJ. Indents made at maximum loads at each end of the indent lines were used to make visible markers allowing Raman microspectroscopy at 1 μm intervals across the DEJ, while using the nanoindent markers for orientation and location. Functional DEJ width estimates were made based on results from nanoindentation and Raman microspectroscopy. DEJ width estimates ranged from 4.7 (±1.2) μm to 6.1 (±1.9) μm based on hardness and 4.9 (±1.1) μm to 6.9 (±1.9) μm based on modulus. DEJ width based on Raman peak intensity variations were 8.0 (±3.2) μm to 8.5 (±3.1) μm based on the phosphate peak, and 7.6 (±3.2) μm to 8.0 (±2.6) μm for C–H stretching mode. These estimates are in the range of DEJ width estimates reported using nanoindentation.

Twins: Measures of birth size at different gestational ages

Means, standard deviations, and empirical centile values are given for birth weight, length and head circumference for twins born at gestational ages 31+ to 42+ weeks. The data are compared with recent results for singletons, and the twins show a deficit that becomes greater as gestational age increases. Although weight may be slightly more affected than the other two measures, the relative growth suppression for twins is quite similar in all three dimensions. Comparatively, the average size of twins born at 33+ weeks gestational age is equal to the 36th centile for singletons; but at 40+ weeks gestational age, the average size for twins is below the 5th centile for singletons.

Educational attainment and cognitive decline in old age

BACKGROUND

Level of education is a well-established risk factor for Alzheimer disease but its relation to cognitive decline, the principal clinical manifestation of the disease, is uncertain.

METHODS

More than 6,000 older residents of a community on the south side of Chicago were interviewed at approximately 3-year intervals for up to 14 years. The interview included administration of four brief tests of cognitive function from which a previously established composite measure of global cognition was derived. We estimated the associations of education with baseline level of cognition and rate of cognitive change in a series of mixed-effects models.

RESULTS

In an initial analysis, higher level of education was related to higher level of cognition at baseline, but there was no linear association between education and rate of change in cognitive function. In a subsequent analysis with terms to allow for nonlinearity in education and its relation to cognitive decline, rate of cognitive decline at average or high levels of education was slightly increased during earlier years of follow-up but slightly decreased in later years in comparison to low levels of education. Findings were similar among black and white participants. Cognitive performance improved with repeated test administration, but there was no evidence that retest effects were related to education or attenuated education's association with cognitive change.

CONCLUSIONS

The results suggest that education is robustly associated with level of cognitive function but not with rate of cognitive decline and that the former association primarily accounts for education's correlation with risk of dementia in old age.

Change in frailty and risk of death in older persons

The authors developed and validated a continuous composite measure of frailty and examined its rate of change in 832 older persons with annual evaluations for up to 8 years. In generalized estimating equation models adjusted for age, sex, and education, there was a significant increase in frailty during follow-up. In a proportional hazards model controlling for age, sex, education, and baseline frailty, each 1-unit increase in annual change in frailty was associated with an almost 5 times the risk of mortality. Using a continuous measure, the authors document that frailty is progressive in some older persons and that its rate of progression is associated with mortality.

Respiratory muscle strength predicts decline in mobility in older persons

OBJECTIVES

To test the hypothesis that respiratory muscle strength is associated with the rate of change in mobility even after controlling for leg strength and physical activity.

METHODS

Prospective study of 890 ambulatory older persons without dementia who underwent annual clinical evaluations to examine change in the rate of mobility over time.

RESULTS

In a linear mixed-effect model adjusted for age, sex, and education, mobility declined about 0.12 unit/year, and higher levels of respiratory muscle strength were associated with a slower rate of mobility decline (estimate 0.043, SE 0.012, p < 0.001). Respiratory muscle strength remained associated with the rate of change in mobility even after controlling for lower extremity strength (estimate 0.036, SE 0.012, p = 0.004). In a model that included terms for respiratory muscle strength, lower extremity strength and physical activity together, all three were independent predictors of mobility decline in older persons. These associations remained significant even after controlling for body composition, global cognition, the development of dementia, parkinsonian signs, possible pulmonary disease, smoking, joint pain and chronic diseases.

CONCLUSION

Respiratory muscle strength is associated with mobility decline in older persons independent of lower extremity strength and physical activity. Clinical interventions to improve respiratory muscle strength may decrease the burden of mobility impairment in the elderly.

Pulmonary function, muscle strength and mortality in old age

Numerous reports have linked extremity muscle strength with mortality but the mechanism underlying this association is not known. We used data from 960 older persons without dementia participating in the Rush Memory and Aging Project to test two sequential hypotheses: first, that extremity muscle strength is a surrogate for respiratory muscle strength, and second, that the association of respiratory muscle strength with mortality is mediated by pulmonary function. In a series of proportional hazards models, we first demonstrated that the association of extremity muscle strength with mortality was no longer significant after including a term for respiratory muscle strength, controlling for age, sex, education, and body mass index. Next, the association of respiratory muscle strength with mortality was attenuated by more than 50% and no longer significant after including a term for pulmonary function. The findings were unchanged after controlling for cognitive function, parkinsonian signs, physical frailty, balance, physical activity, possible COPD, use of pulmonary medications, vascular risk factors including smoking, chronic vascular diseases, musculoskeletal joint pain, and history of falls. Overall, these findings suggest that pulmonary function may partially account for the association of muscle strength and mortality.

Relation of NSAIDs to incident AD, change in cognitive function, and AD pathology

OBJECTIVE

To examine the relation of nonsteroidal anti-inflammatory drugs (NSAIDs) to incident Alzheimer disease (AD), change in cognition, and AD pathology.

METHODS

Participants were 1,019 older Catholic clergy followed up annually for up to 12 years (mean baseline age = 75.0 years, education = 18.1 years, Mini-Mental State Examination score = 28.5), enrolled in the Religious Orders Study, a longitudinal clinical-pathologic study of aging and AD. Clinical evaluations allowed for AD classification and assessment of global cognition and five cognitive domains. NSAIDs were identified by direct medication inspection at baseline and follow-up evaluations. Neuropathologic data were available on 328 deceased participants. AD pathology was summarized as a global measure and as measures of neuritic plaques, diffuse plaques, and neurofibrillary tangles. We used Cox proportional hazards models and mixed models for incident AD and cognitive decline, respectively, and logistic and linear regression for pathologic outcomes, adjusted for age, sex, and education.

RESULTS

Overall, we found no apparent relation of NSAIDs to incident AD (n = 209 cases), change in cognition, or AD pathology. The hazard ratio of incident AD was 1.19 (95% CI 0.87-1.62) comparing those using NSAIDs with those not using NSAIDs at baseline, and 0.84 (95% CI 0.63-1.11) for specific use of aspirin. Findings were similar in analyses in which we considered NSAID use during follow-up. NSAIDs were not related to change in cognition (all p values > 0.14). There was no relation of NSAIDs to global AD pathology or plaques or tangles.

CONCLUSION

These data do not support a strong relation between nonsteroidal anti-inflammatory drugs and Alzheimer disease or cognition. Consistent findings across clinical and pathologic outcomes provide additional confidence in these results.

Intrinsic determinants of temperament

Infant twins have been recruited to participate in a longitudinal assessment of temperament, beginning at three months of age. The twins are brought into a structured laboratory setting and are videotaped as they interact with the mother, with staff personnel, and with each other. The infant's temperament is rated from the videotapes, and additional data are obtained by having the parents fill out the Infant/Toddler Temperament Questionnaire at each visit. A neonatal assessment has also been done for most twins to obtain initial measures of irritability, reactivity and soothability. Monozygotic twins showed high concordance for irritability as neonates, and for ratings of emotional tone at 12 months. Monozygotic twins also tended to show synchronized patterns of change between ages. The questionnaire ratings correlated significantly with the laboratory ratings at six and 12 months, and this convergent linkage between two sources argues for a core temperament profile that manifests itself with some consistency.

Processing resources reduce the effect of Alzheimer pathology on other cognitive systems

The cognitive abilities of older persons vary greatly, even among those with similar amounts of Alzheimer disease (AD) pathology, suggesting differences in neural reserve. Although its neurobiologic basis is not well understood, reserve may reflect differences in the ability to compensate for the deleterious effects of pathology by recruiting alternative or additional brain networks to perform a specific task. If this is an effective compensatory strategy, then involvement of additional cognitive systems may help maintain function in other cognitive systems despite the accumulation of pathology.

OBJECTIVE

We tested the hypothesis that processing resources, specifically perceptual speed and working memory, modify the associations of AD pathology with other cognitive systems.

METHOD

A total of 103 older participants of the Rush Memory and Aging Project underwent detailed annual clinical evaluations and brain autopsy. Five cognitive systems including perceptual speed, working memory, semantic memory, visuospatial abilities, and episodic memory were assessed proximate to death, and AD pathology including tau tangles and amyloid load were quantified postmortem.

RESULTS

In multiple regression models adjusted for age, sex, and education, processing resources reduced the associations of tangles with other cognitive systems, such that persons with higher levels of perceptual speed and working memory performed better on semantic memory and visuospatial abilities despite the burden of tangles. Perceptual speed also reduced the associations of amyloid with semantic memory, visuospatial abilities, and episodic memory.

CONCLUSION

These findings suggest that processing resources may help compensate for the deleterious effects of Alzheimer disease pathology on other cognitive systems in older persons.

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.