EFFECT OF AGING ON MACULAR FEATURES OF X-LINKED RETINOSCHISIS ASSESSED WITH OPTICAL COHERENCE TOMOGRAPHY

X-linked retinoschisis (XLRS) is one of the most common causes of macular degeneration in young men. The purpose of this study was to use optical coherence tomography combined with ophthalmoscopy to study the effects of aging on the morphologic changes associated with XLRS.

Electrophysiological and behavioral correlates of stable automatic semantic retrieval in aging

Previous studies have shown both declining and stable semantic-memory abilities during healthy aging. There is consistent evidence that semantic processes involving controlled mechanisms weaken with age. In contrast, results of aging studies on automatic semantic retrieval are often inconsistent, probably due to methodological limitations and differences. The present study therefore examines age-related alterations in automatic semantic retrieval and memory structure with a novel combination of critical methodological factors, i.e., the selection of subjects, a well-designed paradigm, and electrophysiological methods that result in unambiguous signal markers. Healthy young and elderly participants performed lexical decisions on visually presented word/non-word pairs with a stimulus onset asynchrony (SOA) of 150 ms. Behavioral and electrophysiological data were measured, and the N400-LPC complex, an event-related potential component sensitive to lexical-semantic retrieval, was analyzed by power and topographic distribution of electrical brain activity. Both age groups exhibited semantic priming (SP) and concreteness effects in behavioral reaction time and the electrophysiological N400-LPC complex. Importantly, elderly subjects did not differ significantly from the young in their lexical decision and SP performances as well as in the N400-LPC SP effect. The only difference was an age-related delay measured in the N400-LPC microstate. This could be attributed to existing age effects in controlled functions, as further supported by the replicated age difference in word fluency. The present results add new behavioral and neurophysiological evidence to earlier findings, by showing that automatic semantic retrieval remains stable in global signal strength and topographic distribution during healthy aging.

Effect of Alzheimer caregiving stress and age on frailty markers interleukin-6, C-reactive protein, and D-dimer

BACKGROUND: Elevated plasma levels of interleukin (IL)-6, C-reactive protein (CRP), and D-dimer belong to the biological alterations of the "frailty syndrome," defining increased vulnerability for diseases and mortality with aging. We hypothesized that, compatible with premature frailty, chronic stress and age are related in predicting inflammation and coagulation activity in Alzheimer caregivers. METHODS: Plasma IL-6, CRP, and D-dimer levels were measured in 170 individuals (mean age 73 +/- 9 years; 116 caregivers, 54 noncaregiving controls). Demographic factors, diseases, drugs, and lifestyle variables potentially affecting inflammation and coagulation were obtained by history and adjusted for as covariates in statistical analyses. RESULTS: Caregivers had higher mean levels of IL-6 (1.38 +/- 1.42 vs 1.00 +/- 0.92 pg/mL, p =.032) and of D-dimer (723 +/- 530 vs 471 +/- 211 ng/mL, p <.001) than controls had. CRP levels were similar between groups (p =.44). The relationship between caregiver status and D-dimer was independent of covariates (p =.037) but affected by role overload. Age accounted for much of the relationship with IL-6. After controlling for covariates, the interaction between caregiver status and age was significant for D-dimer (beta =.20, p =.029) and of borderline significance for IL-6 (beta =.17, p =.090). Post hoc regression analyses indicated that, among caregivers, age was significantly correlated with both D-dimer (beta =.50, p <.001) and IL-6 (beta =.38, p =.001). Among controls, however, no significant relationship was observed between age and either D-dimer or IL-6. CONCLUSIONS: The interaction between caregiving status and age for D-dimer and IL-6 suggests the possibility that older caregivers could be at risk of a more rapid transition to the frailty syndrome and clinical manifestations of cardiovascular diseases.

Electrocardiographic PR interval and adverse outcomes in older adults: the Health, Aging, and Body Composition study

BACKGROUND The electrocardiographic PR interval increases with aging, differs by race, and is associated with atrial fibrillation (AF), pacemaker implantation, and all-cause mortality. We sought to determine the associations between PR interval and heart failure, AF, and mortality in a biracial cohort of older adults. METHODS AND RESULTS The Health, Aging, and Body Composition (Health ABC) Study is a prospective, biracial cohort. We used multivariable Cox proportional hazards models to examine PR interval (hazard ratios expressed per SD increase) and 10-year risks of heart failure, AF, and all-cause mortality. Multivariable models included demographic, anthropometric, and clinical variables in addition to established cardiovascular risk factors. We examined 2722 Health ABC participants (aged 74±3 years, 51.9% women, and 41% black). We did not identify significant effect modification by race for the outcomes studied. After multivariable adjustment, every SD increase (29 ms) in PR interval was associated with a 13% greater 10-year risk of heart failure (95% confidence interval, 1.02-1.25) and a 13% increased risk of incident AF (95% confidence interval, 1.04-1.23). PR interval >200 ms was associated with a 46% increased risk of incident heart failure (95% confidence interval, 1.11-1.93). PR interval was not associated with increased all-cause mortality. CONCLUSIONS We identified significant relationships of PR interval to heart failure and AF in older adults. Our findings extend prior investigations by examining PR interval and associations with adverse outcomes in a biracial cohort of older men and women.

Age affects the adjustment of cognitive control after a conflict: evidence from the bivalency effect

Age affects cognitive control. When facing a conflict, older adults are less able to activate goal-relevant information and inhibit irrelevant information. However, cognitive control also affects the events after a conflict. The purpose of this study was to determine whether age affects the adjustment of cognitive control following a conflict. To this end, we investigated the bivalency effect, that is, the performance slowing occurring after the conflict induced by bivalent stimuli (i.e., stimuli with features for two tasks). In two experiments, we tested young adults (aged 20-30) and older adults (aged 65-85) in a paradigm requiring alternations between three tasks, with bivalent stimuli occasionally occurring on one task. The young adults showed a slowing for all trials following bivalent stimuli. This indicates a widespread and long-lasting bivalency effect, replicating previous findings. In contrast, the older adults showed a more specific and shorter-lived slowing. Thus, age affects the adjustment of cognitive control following a conflict.

Metabolomics Reveals Aging-associated Attenuation of Noninvasive Radiation Biomarkers in Mice: Potential Role of Polyamine Catabolism and Incoherent DNA Damage-repair

Development of methods for rapid screening and stratification of subjects after exposure is an integral part of countermeasures against radiation. The potential demographic and exposure history-related heterogeneity of exposed populations warrants robust biomarkers that withstand and reflect such differences. In this study, the effect of aging and repeated exposure on the metabolic response to sublethal irradiation was examined in mice using UPLC-ESI-QTOF mass spectrometry. Aging attenuated postexposure elevation in excretions of DNA damage biomarkers as well as N(1)-acetylspermidine. Although N(1)-acetylspermidine and 2'-deoxyuridine elevation was highly correlated in all age groups, xanthine and N(1)-acetylspermidine elevation was poorly correlated in older mice. These results may reflect the established decline in DNA damage-repair efficiency associated with aging and indicate a novel role for polyamine metabolism in the process. Although repeated irradiation at long intervals did not affect the elevation of N(1)-acetylspermidine, 2'-deoxyuridine, and xanthine, it did significantly attenuate the elevation of 2'-deoxycytidine and thymidine compared to a single exposure. However, these biomarkers were found to identify exposed subjects with accuracy ranging from 82% (xanthosine) to 98% (2'-deoxyuridine), irrespective of their age and exposure history. This indicates that metabolic biomarkers can act as robust noninvasive signatures of sublethal radiation exposure.

Effect of Cognitive Impairment on Driving-Relevant Cognition in Older Persons

Intact cognitive abilities are fundamental for driving. Driving-relevant cognition may be affected in older drivers due to aging or cognitive impairment. The aim of this study was to investigate the effects of cognitive impairment on driving-relevant cognition in older persons. Performance in selective and divided attention, eye-hand-coordination, executive functions and the ability to regulate distance and speed of 18 older persons with CI-Group (cognitive impairment group) was compared to performance of older control group (18 age and gender-matched cognitively normal subjects) and young control group (18 gender-matched young subjects). The CI-Group showed poorer performance than the other two control groups in all cognitive tasks (significance level (p) < 0.001, effect size (partial η2) = 0.63). Differences between cognitively impaired and cognitively normal subjects were still significant after controlling for age (effect sizes from 0.14 to 0.28). Dual tasking affected performance of cognitively impaired subjects more than performance of the other two groups (p = 0.016, partial η2 = 0.14). Results show that cognitive impairment has age-independent detrimental effects on selective and divided attention, eye-hand-coordination, executive functions and the ability to regulate distance and speed. Largest effect sizes are found for reaction times in attention tasks.

Corporate aging and investment decisions

Paper I: Corporate aging and internal resource allocation Abstract Various observers argue that established firms are at a disadvantage in pursuing new growth opportunities. In this paper, we provide systematic evidence that established firms allocate fewer resources to high-growth lines of business. However, we find no evidence of inefficient resource allocation in established firms. Redirecting resources from high-growth to low-growth lines of business does not result in lower profitability. Also, resource allocation towards new growth opportunities does not increase when managers of established firms are exposed to takeover and product market threats. Rather, it seems that conservative resource allocation strategies are driven by pressures to meet investors’ expectations. Our empirical evidence, thus, favors the hypothesis that established firms wisely choose to allocate fewer resources to new growth opportunities as external pressures force them to focus on efficiency rather than novelty (Holmström 1989). Paper II: Corporate aging and asset sales Abstract This paper asks whether divestitures are motivated by strategic considerations about the scope of the firm’s activities. Limited managerial capacity implies that exploiting core competences becomes comparatively more attractive than exploring new growth opportunities as firms mature. Divestitures help stablished firms free management time and increase the focus on core competences. The testable implication of this attention hypothesis is that established firms are the main sellers of assets, that their divestiture activity increases when managerial capacity is scarcer, that they sell non-core activities, and that they return the divestiture proceeds to the providers of capital instead of reinvesting them in the firm. We find strong empirical support for these predictions. Paper III: Corporate aging and lobbying expenditures Abstract Creative destruction forces constantly challenge established firms, especially in competitive markets. This paper asks whether corporate lobbying is a competitive weapon of established firms to counteract the decline in rents over time. We find a statistically and economically significant positive relation between firm age and lobbying expenditures. Moreover, the documented age-effect is weaker when firms have unique products or operate in concentrated product markets. To address endogeneity, we use industry distress as an exogenous nonlegislative shock to future rents and show that established firms are relatively more likely to lobby when in distress. Finally, we provide empirical evidence that corporate lobbying efforts by established firms forestall the creative destruction process. In sum, our findings suggest that corporate lobbying is a competitive weapon of established firms to retain profitability in competitive environments.