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Age Dependence (age + dependence)
Selected AbstractsHIERARCHICAL BAYESIAN MODELLING OF SOCIAL VARIATION IN THE AGE DEPENDENCE OF DISABILITY PREVALENCEAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 4 2005Patrick Graham Summary Motivated by a study of social variation in the relationship of functional limitation prevalence to age, this paper examines methods for modelling social variation in health outcomes. It is argued that, from a Bayesian perspective, modelling the dependence of functional limitation prevalence on age separately for each social group, corresponds to an implausible prior model, in addition to leading to imprecise estimates for some groups. The alternative strategy of fitting a single model, perhaps including some age-by-group interactions but omitting higher-order interactions, requires a strong prior commitment to the absence of such effects. Hierarchical Bayesian modelling is proposed as a compromise between these two analytical approaches. Under all hierarchical Bayes analyses there is strong evidence for an ethnic group difference in limitation prevalence in early- to mid-adulthood among tertiary-qualified males. In contrast, the single-model approach largely misses this effect, while the group-specific analyses exhibit an unrealistically large degree of heterogeneity in gender-education-specific ethnicity effects. The sensitivity of posterior inferences to prior specifications is studied. [source] Age Dependence of the Human Skeletal Muscle Stem Cell in Forming Muscle TissueARTIFICIAL ORGANS, Issue 3 2006Ralf Schäfer Abstract:, Human skeletal muscle stem cells from healthy donors aged 2,82 years (n = 13) and from three children suffering from Duchenne Muscular Dystrophy (DMD) were implanted into soleus muscles of immunoincompetent mice and were also expanded in vitro until senescence. Growth of implanted cells was quantified by structural features and by the amount of human DNA present in a muscle. Proliferative capacity in vitro and in vivo was inversely related to age of the donor. In vitro, a decline of about two mean population doublings (MPDs) per 10 years of donor's age was observed. Muscle stem cells from DMD children were prematurely aged. In general, cell preparations with low or decreasing content in desmin-positive cells produced more MPDs than age-matched high-desmin preparations and upon implantation more human DNA and more nonmyogenic than myogenic tissue. Thus, a "Desmin Factor" was derived which predicts "quality" of the human muscle tissue growing in vivo. This factor may serve as a prognostic tool. [source] Age dependence of cataract induced by ultraviolet radiation-B in miceACTA OPHTHALMOLOGICA, Issue 2007Y ZHANG Purpose: To investigate for the C57BL/6 mouse if there is an age dependence of the dose-response function for in vivo UVR-300 nm induced forward light scattering in the lens. Methods: Each of four age groups of 25 mice aged 3, 6, 12, or 24 weeks were randomly distributed on five age group specific UVR-B dose levels. The dose levels selected for each age group were derived from the expected maximum tolerable dose (MTD). Expected MTDs were set to 1.9, 3.2, 4.8, and 6.0 kJ/m^2 for the 3, 12, and 24 weeks mice, respectively, based on published data for the albino Sprague Dawley rat. Each animal was unilaterally exposed to UVR-B to the pre-determined dose, delivered during 15 minutes. All mice were sacrificed two days after exposure and both lenses were extracted for; macroscopic imaging in incident illumination against a grid and in dark-field illumination, and measurement of intensity of forward light scattering. The difference of intensity of forward light scattering between the exposed and the contralateral not exposed lens was fitted against dose received using regression based on a second order polynomial model. Results: Two days after exposure, subcapsular opacities were observed in the exposed lenses from all dose groups except at 0 kJ/m^2. In all age groups, the difference of intensity of forward light scattering increased with increasing UVR-B dose. The increase was age dependent. Conclusions: In the pigmented C57BL/6 mouse, an increasing in vivo dose of UVR-300 nm induces an increasing intensity of forward light scattering that is age dependent in the age interval 3-24 weeks. This finding should be considered in future design of experiments on UVR-effects to the mouse lens. [source] Prolonged Febrile Seizures Are Associated with Hippocampal Vasogenic Edema and Developmental ChangesEPILEPSIA, Issue 9 2006Rod C. Scott Summary:,Purpose: There is mounting evidence that a prolonged febrile seizure (PFS) can cause acute hippocampal edema although the nature of that edema remains uncertain. The principal aims of the current study were: (1) to use apparent diffusion coefficient (ADC) measurements to further characterize the hippocampal edema previously identified within 5 days of a PFS, and (2) to determine whether the age dependency of ADC in the hippocampus is different in patients when compared to a control population following a PFS. Methods: Diffusion weighted imaging was acquired in 23 children within 5 days of a PFS, and in 14 of these children a mean of 5.5 months later. Twenty-four control children were enrolled. Results: There was a reduction in ADC between the acute and follow-up investigations [mean reduction = 0.0072 mm2/s/month since PFS (95% confidence interval; 0.0001,0.014 mm2/s/month since PFS), p = 0.048] consistent with early vasogenic edema, followed by recovery in children investigated within 2 days of a PFS. In addition, the behavior of ADC with respect to age was different in patients when compared to control subjects [mean difference in slope =,0.155 mm2/s/log10 age (95% confidence interval; ,0.290,0.0203 mm2/s/log10 age), p = 0.029], in that the expected age dependence was observed only in the control subjects. Conclusion: We suggest that these latter findings are most consistent with a preexisting developmental hippocampal abnormality that may predispose individuals to having a PFS. [source] THE EFFECTS OF GENOTYPE, AGE, AND SOCIAL ENVIRONMENT ON MALE ORNAMENTATION, MATING BEHAVIOR, AND ATTRACTIVENESSEVOLUTION, Issue 11 2005Lisa K. Miller Abstract The traits thought to advertise genetic quality are often highly susceptible to environmental variation and prone to change with age. These factors may either undermine or reinforce the potential for advertisement traits to signal quality depending on the magnitude of age-dependent expression, environmental variation, and genotype-age and genotype-environment interaction. Measurements of the magnitude of these effects are thus a necessary step toward assessing the implications of age dependence and environmental variability for the evolution of signals of quality. We conducted a longitudinal study of male guppies (Poecilia reticulata) from 22 full-sibling families. Each fish was assigned at maturity to one of three treatments in order to manipulate his allocation of resources to reproduction: a control in which the male was kept alone, a courtship-only treatment in which he could see and court a female across a clear partition, and a mating treatment in which he interacted freely with a female. We measured each male's size, ornamental color patterns, courtship, attractiveness to females, and mating success at three ages. Size was influenced by treatment and age-treatment interactions, indicating that courtship and mating may impose costs on growth. Tail size and color patterns were influenced by age but not by treatment, suggesting fixed age-dependent trajectories in these advertisement traits. By contrast, display rate and attempted sneak copulation rate differed among treatments but not among ages, suggesting greater plasticity of these behavioral traits. As a result of the different patterns of variation in ornamentation and behavior, male attractiveness and mating success responded to male age, treatment, and the interaction between age and treatment. Neither age nor treatment obscured the presence of genetic variation, and the genetic relationship between male ornamentation and attractiveness remained the same among treatments. Our findings suggest that neither age-dependent variation nor environmentally induced variation in reproductive effort is likely to undermine the reliability of male signaling. [source] Site-Specific Deterioration of Trabecular Bone Architecture in Men and Women With Advancing AgeJOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2008Eva-Maria Lochmüller Abstract We tested the hypothesis that the age dependence of trabecular bone microstructure differs between men and women and is specific to skeletal site. Furthermore, we aimed to investigate the microstructural pattern of bone loss in aging. Microstructural properties of trabecular bone were measured in vitro in 75 men and 75 age-matched women (age, 52,99 yr) using ,CT. Trabecular bone samples were scanned at a 26-,m isotropic resolution at seven anatomical sites (i.e., distal radius, T10 and L2 vertebrae, iliac crest, femoral neck and trochanter, and calcaneus). DXA measurements were obtained at the distal radius and proximal femur and QCT was used at T12. No significant decrease in bone density or structure with age was found in men using ,CT, DXA, or QCT at any of the anatomical sites. In women, a significant age-dependent decrease in BV/TV was observed at most sites, which was strongest at the iliac crest and weakest at the distal radius. At most sites, the reduction in BV/TV was associated with an increase in structure model index, decrease in Tb.N, and an increase in Tb.Sp. Only in the calcaneus was it associated with a significant decrease in Tb.Th. In conclusion, a significant, site-specific correlation of trabecular bone microstructure with age was found in women but not in men of advanced age. The microstructural basis by which a loss of BV/TV occurs with age can vary between anatomical sites. [source] Ageing in granular aluminium insulating thin filmsANNALEN DER PHYSIK, Issue 12 2009J. Delahaye Abstract We present a new set of electrical field effect measurements on granular aluminium insulating thin films. We have explored how the conductance relaxations induced by gate voltage changes depend on the age of the system, namely the time elapsed since its quench at low temperature. A clear age dependence of the relaxations is seen, qualitatively similar to ageing effects seen in other well studied glassy systems such as spin glasses or polymers. We explain how our results differ from the previous ones obtained with different protocols in indium oxide and granular aluminium thin films. Our experimental findings bring new information on the dynamics of the system and put new constraints on the theoretical models that may explain slow conductance relaxations in disordered insulators. [source] MLE and Bayesian Inference of Age-Dependent Sensitivity and Transition Probability in Periodic ScreeningBIOMETRICS, Issue 4 2005Dongfeng Wu Summary This article extends previous probability models for periodic breast cancer screening examinations. The specific aim is to provide statistical inference for age dependence of sensitivity and the transition probability from the disease free to the preclinical state. The setting is a periodic screening program in which a cohort of initially asymptomatic women undergo a sequence of breast cancer screening exams. We use age as a covariate in the estimation of screening sensitivity and the transition probability simultaneously, both from a frequentist point of view and within a Bayesian framework. We apply our method to the Health Insurance Plan of Greater New York study of female breast cancer and give age-dependent sensitivity and transition probability density estimates. The inferential methodology we develop is also applicable when analyzing studies of modalities for early detection of other types of progressive chronic diseases. [source] Is there a role for dynamic retinal vessel analysis in internal medicine?ACTA OPHTHALMOLOGICA, Issue 2008IM LANZL Purpose Human retinal vessels and their reaction to stimuli change during life and in disease due to physiological, genetic and pathological influences. Using the Dynamic Vessel Analyzer (DVA, Fa. IMEDOS, Jena) it is possible to assess changes in retinal vessel diameters in response to vasoactive stimuli in real time and non-invasively. Methods Retinal arterial vessel reaction in the natural time course and to the average of 3 consecutive monochromatic flicker stimulations (530-600 nm, 12,5 Hz, 20 s) with a 80 s observation pause between stimulations was investigated in healthy volunteers of different age groups, obese patients, diabetes type 1 patients, systemic hypertensive patients and patients with lysosomal storage disease. Statistical data analysis of vessel reactions independent from the DVA program was performed. Results There is a statistically significant difference in retinal vascular behaviour in different age groups in a healthy population. The same is true between a healthy population and each of the diseases investigated. Lysosomal storage disease however demonstrated an increase in dilation following flicker stimulation compared to normal persons. Conclusion Flicker stimulation of the retina light evokes a prompt vessel reaction in all healthy subjects. We could demonstrate an age dependence of the retinal arterial reaction in medically healthy persons and in hypertension, diabetes and obese patients. From the increased reaction in lysosomal storage disease further understanding of different factors leading to the vascular reaction to stimuli may be derived. Application of flicker stimulus to retinal vessels represents a method to assess the endothelial function of vessels which is important to understand in systemic disease. [source] Age dependence of cataract induced by ultraviolet radiation-B in miceACTA OPHTHALMOLOGICA, Issue 2007Y ZHANG Purpose: To investigate for the C57BL/6 mouse if there is an age dependence of the dose-response function for in vivo UVR-300 nm induced forward light scattering in the lens. Methods: Each of four age groups of 25 mice aged 3, 6, 12, or 24 weeks were randomly distributed on five age group specific UVR-B dose levels. The dose levels selected for each age group were derived from the expected maximum tolerable dose (MTD). Expected MTDs were set to 1.9, 3.2, 4.8, and 6.0 kJ/m^2 for the 3, 12, and 24 weeks mice, respectively, based on published data for the albino Sprague Dawley rat. Each animal was unilaterally exposed to UVR-B to the pre-determined dose, delivered during 15 minutes. All mice were sacrificed two days after exposure and both lenses were extracted for; macroscopic imaging in incident illumination against a grid and in dark-field illumination, and measurement of intensity of forward light scattering. The difference of intensity of forward light scattering between the exposed and the contralateral not exposed lens was fitted against dose received using regression based on a second order polynomial model. Results: Two days after exposure, subcapsular opacities were observed in the exposed lenses from all dose groups except at 0 kJ/m^2. In all age groups, the difference of intensity of forward light scattering increased with increasing UVR-B dose. The increase was age dependent. Conclusions: In the pigmented C57BL/6 mouse, an increasing in vivo dose of UVR-300 nm induces an increasing intensity of forward light scattering that is age dependent in the age interval 3-24 weeks. This finding should be considered in future design of experiments on UVR-effects to the mouse lens. [source] Sex Modulates the Arrhythmogenic Substrate in Prepubertal Rabbit Hearts with Long QT 2JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2005Ph.D., TONG LIU M.D. Females have a greater susceptibility to Torsade de Pointes in congenital and drug-induced long QT syndrome (LQTS) that has been attributed to the modulation of ion channel expression by sex hormones. However, little is known regarding sex differences in pre-puberty, that is, before the surge of sexual hormones. In patients with congenital LQTS types 1 and 2, male children tend to have a greater occurrence of adverse events, especially in 10,15 year olds, than their female counterpart. To evaluate whether the rabbit model of drug-acquired LQTS exhibits similar age dependences, hearts of prepubertal rabbits were perfused, mapped optically to record action potentials (APs) and treated with an IKr blocker, E4031 to elicit LQTS2. As expected, AP durations (APD) were significantly longer in female (n = 18) than male hearts (n = 10), at long cycle length. Surprisingly, E4031 (50,250 nM) induced a greater prolongation of APDs in male than in female hearts, and in both genders reversed the direction of repolarization (apex , base to base , apex), enhancing dispersions of repolarization. Furthermore, in male hearts, E4031 (0.5 ,M) elicited early afterdepolarizations (EADs) that progressed to polymorphic ventricular tachycardia (PVT) (n = 7/10) and were interrupted by isoproterenol (40 nM) and prevented by propranolol (0.5,2.5 ,M). In female hearts, E4031 (0.5 ,M) produced marked prolongations of APDs yet few EADs with no progression to PVT (n = 16/18). Thus, sex differences are opposite in prepubertal versus adult rabbits with respect to E4031-induced APD prolongation, EADs and PVT, underscoring the fact that APD prolongation alone is insufficient to predict arrhythmia susceptibility. [source] | |||||||||||||