No description available.

This study was carried out in response to the policy attention directed at older people discharged from hospital with ill-defined conditions, or signs and symptoms related disease. In England there has been an increase in incidence of this type of hospital admission and policy suggests that patients with these codes have fewer medical/physiological and more ‘social’ conditions that could be better managed in community settings. Currently however, this population has not been characterised. Description of the functional and physiological status of these patients is essential for the planning of future health and social care services. Patients with ill-defined conditions were described via a cross-sectional study of 80 patients aged over 70 years admitted to hospital with collapse/falls. Number of chronic diseases and prescribed medications were obtained from the medical records. Routine blood tests were taken and serum cytokine concentrations (IL-1β, IL-6, TNF-α, IFN-γ) were measured. Deprivation score, functional status, depression and the prevalence of frailty were ascertained. 35 patients received ill-defined condition codes, 45 received other codes. Patients with ‘illdefined conditions’ had normal routine blood results but very high serum concentrations of pro-inflammatory cytokines which did not correlate with number of chronic diseases indicating considerable medical problems. As the policy had suggested, they also had prevalent functional impairment (65.7%), high rates of frailty (77.1%) and pre-frailty (14.3%), and depression (42.9%). Patients with ill-defined conditions had poor outcomes evident in the high readmission (60%) and mortality (20%) rates. Patients were hospitalised for a statistically significantly shorter period than patients with other codes (p<.05) and functional limitations and depression were associated with a longer length of stay. Increasing deprivation and TNF-α concentration were associated with an increase in the odds of an illdefined condition diagnosis at discharge. The association between functional limitations, frailty, chronic disease and depression add considerable complexity to the health of older people with ill-defined conditions. However, the prevalence of multiple morbidity, high serum concentrations of inflammatory markers and poor outcomes indicate that they also have considerable medical problems that may be largely unmet. These medical problems may result from chronic disease symptom crises and manifest as geriatric conditions for which there are no appropriate International Classification of Diseases (ICD-10) codes. The results of this study indicate a need for reevaluation of the ICD-10 system to incorporate the health problems faced by older people and further research into the effect of a more comprehensive community-based chronic disease management that aims to enable frail older people to maintain health and independence at home and prevent readmission in patients with ill-defined conditions.

No description available.

This submission for PhD is based around a series of thematic and original research studies, which have been published during the past seven years (2001 to 2007), focused upon arm crank ergometry exercise testing. A number of topical issues have been considered, including: 1) the development of fundamental exercise protocols; 2) the assessment of oxygen uptake (VO2) kinetics; 3) the assessment of external power production during sprint arm crank ergometry, and 4) the design and implementation of novel equipment configurations and research designs. During preliminary testing we demonstrated that the selection of an imposed crank rate was an important consideration. In another study we also demonstrated that it was feasible to use either step or ramp incremental exercise tests for the purpose of establishing peak physiological responses during arm crank ergometry. Two further studies considered the measurement of external peak and mean power production during sprint arm crank ergometry. The first of these studies compared measurement techniques. A follow-up publication considered the reproducibility of uncorrected peak and mean values of power output. In the final publication an interdisciplinary approach was employed. This study examined how crank configuration (asynchronous vs. synchronous) affected the magnitude and pattern of muscle activity, and torque production at two work rates. Our findings demonstrated the complexity of arm crank ergometry as the activity of muscles of the arms, shoulders and legs became progressively involved as external work rate increased from 50 to 100 W. Based on parameters associated with the pattern of torque profile, it was speculated that the asynchronous crank configuration was more efficient for the group of able-bodied participants.

Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation method that involves the application of weak electric currents to the scalp. tACS has the potential to be an inexpensive, easily administrable, and well-tolerated multi-purpose tool for cognitive and clinical neuroscience as it could be applied to establish the functional role of rhythmic brain activity, and to treat neural disorders, in particular those where these rhythms have gone awry. However, the mechanisms by which tACS produces both "online" and "offline" effects (that is, those that manifest during stimulation and those that last beyond stimulation offset) are to date still poorly understood. If the potential of tACS is to be harnessed effectively to alter brain activity in a controlled manner, it is fundamental to have a good understanding of how tACS interacts with neuronal dynamics, and of the conditions that promote its effect. This thesis describes three experiments that were conducted to elucidate the mechanisms by which tACS interacts with underlying neural network activity. Experiments 1 and 2 investigated the mechanism by which tACS at alpha frequencies (8 12 Hz, α-tACS) over occipital cortex induces the lasting aftereffects on posterior α power that were previously described in the literature. Two mechanisms have been suggested to underlie alpha power enhancement after α tACS: entrainment of endogenous brain oscillations and/or changes in oscillatory neural networks through spike timing-dependent plasticity (STDP). In Experiment 1, we tested to what extent plasticity can account for tACS-aftereffects when controlling for entrainment characteristics. To this end, we used a novel, intermittent α-tACS protocol and investigated the strength of the aftereffect as a function of phase continuity between successive tACS episodes, as well as the match between stimulation frequency and individual alpha frequency (IAF). Alpha aftereffects were successfully replicated with enhanced α power after intermittent stimulation compared to sham. These aftereffects did not exhibit any of the expected characteristics of prolonged entrainment in that they were independent of tACS phase-continuity and did not show stable phase alignment or synchronisation to the stimulation frequency. These results indicate that prolonged entrainment is insufficient to explain the aftereffects and suggest that the latter emerge through some form of network plasticity. To clarify the nature of these plasticity mechanisms, we then aimed to assess whether STDP could explain the α power increase. We developed a conceptual STDP model that predicted bi-directional changes in α power depending on the relative mismatch between the tACS frequency and IAF. After observing in Experiment 1 that tACS at frequencies slightly lower than the IAF produced α enhancement, Experiment 2 used a similar intermittent protocol that manipulated tACS frequency to be either slightly lower or higher than IAF to respectively enhance or suppress α activity. In addition, a control condition with continuous stimulation aimed to replicate previous results from other groups. However, we did not observe a systematic α power change in any of the active conditions. The lack of consistency between the two experiments raises concerns regarding the reproducibility and effect size of tACS aftereffects. The third experiment investigated the mechanism of online effects and tested predictions that were based on the assumption that entrainment is the underlying process mediating behavioural changes during tACS. We capitalised on two well-described phenomena: firstly, the association between α power lateralisation and visuospatial attention, and secondly, the fluctuation of perceptual performance with α phase. Specifically, the experiment tested whether event-related α-tACS applied over right parieto-occipital cortex can induce a visuospatial bias in a peripheral dot detection task that would reflect α power lateralisation, and whether detection performance depends on the phase of the tACS waveform. In control trials either no tACS or 40 Hz-tACS (gamma) was applied to make use of the putative opposing roles of alpha and gamma oscillations in visual processing. As expected from lateralised enhancement of alpha oscillations, visual detection accuracy was weakly impaired for targets presented in the left visual field, contralateral to tACS. However, this effect was neither frequency specific nor waveform phase-dependent. Therefore, it is unlikely that the negative effect of tACS on visuospatial performance reflects entrainment. Overall, the results of these experiments only partially met our hypotheses. Experiment 1 produced the α enhancement that was expected based on the literature while the follow-up experiment failed to reproduce these results under similar conditions. This outcome demonstrates at best that tACS aftereffects on α activity are not robust, may vary widely across individuals, and might be extremely sensitive to small changes in experimental parameters and state variables. The results of the third experiment call into question the assumption of online entrainment as basis for the observed behavioural effect. These findings point to the need for improved methodology, for more systematic and exhaustive exploration of the relative effects of tACS across different parameter settings, tasks, and individuals; and for the replication of promising but thus far often anecdotal results. They also inspire guidelines for more informative experimental designs.

No description available.

The overarching aim of this thesis was to better understand the behavioural, cognitive, and neural corollaries of blunted cardiovascular and/or cortisol reactions to acute psychological stress. As such, it was also concerned to further test the proposition that blunted cardiovascular and cortisol reactions to acute psychological stress are markers of an unconscious dysfunction in the motivational areas of the brain. These aims were achieved by using a mixed methods interdisciplinary approach encompassing both laboratory stress studies and secondary analyses of epidemiological datasets. Chapter 2 adduced evidence that blunted cardiovascular and cortisol reactivity was associated with a non-substance addiction, namely exercise dependence. Chapter 3 demonstrated that blunted cardiovascular and cortisol reactivity was related to disordered eating behaviour. Differences in stress reactivity between healthy controls and exercise dependent individuals or disordered eaters could not be explained by actual stress task performance, how engaged or how stressful participants found the stress task, cardio-respiratory fitness, and a number of other potential confounders. Chapters 4, 5, and 6 demonstrated that poor cognitive ability was associated with blunted stress reactivity retrospectively, cross-sectionally, and prospectively. Additionally, Chapter 6 demonstrated that blunted cardiac reactivity predicted cognitive decline over a 7 year period. Chapter 7 revealed brain activation differences between pre-determined exaggerated and blunted cardiac stress reactors during an acute stress exposure in a fMRI paradigm. Blunted cardiac reactors showed hypo-activation in the areas of the brain associated with motivation and emotion compared to exaggerated reactors. There were no reactivity group differences in subjective measures of the stressfulness and difficulty of and engagement with the stress task. Overall, the research reported in this thesis provides further evidence that blunted cardiovascular and cortisol reactions to stress are associated with a number of adverse health and behavioural outcomes and may be a peripheral marker of some form of disengagement in those areas of the brain that support motivated behaviour.

This thesis explored internal and external predictors of fruit and vegetable intake in children of different age groups. The first sample were toddlers between 2-3 years old and the second sample were children between 5-9 years old. Intake of fruit was analysed separately from intake of vegetables, and subgroups of fruit and vegetables with strong sensory properties were also analysed separately. The results showed that in the older sample lifetime exposure to variety of different fruit and vegetables was positively associated with quantity and diversity of fruit and vegetables consumed. In toddlers, liking of fruit and vegetables was not directly linked to their intake. In children of less controlling mothers fruit liking was positively associated with fruit intake and children of the more controlling mothers ate fruit independent of fruit liking. Past history of middle ear infections may affect adiposity and fruit and vegetable intake. Finally, individual levels of sensitivity to sweet taste may affect adiposity and intake of cruciferous vegetables and non-astringent fruit in school-age children. Parental intake was the strongest predictor of intake in both age groups. The results of this thesis show that fruit and vegetables have different predictors of intake and need to be considered separately.