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For adults aged 45 and over in the United Kingdom (UK), osteoarthritis is a common reason for consultation with primary care. Cardiovascular disease (CVD) is a common comorbidity with osteoarthritis; two in five people with osteoarthritis also have CVD. In the UK, primary care is often the first point of contact for people in need of osteoarthritis management and CVD preventive services. This thesis aims to assess the prevalence of CVD risk factors, the level of CVD risk and outcomes in primary care consulters with osteoarthritis in comparison to those without osteoarthritis. To address this question, the thesis includes a series of retrospective cohort studies using CPRD GOLD, a large representative primary care EHR database, and linked data in the UK between 1992-2017. The consistently higher prevalence of modifiable cardiovascular risk factors (CVRFs), variables that are associated with a higher risk of CVD events, in the osteoarthritis population was revealed in chapter 2 and the socioeconomic inequality in these CVRFs was found in chapter 3. The thesis could then try to understand that if ruling out the impact of CVRFs, what is the excess risk of CVD due to osteoarthritis. The thesis then tried to use the established risk score (sex-specific Framingham risk score) to predict the CVD risk and to assess the following preventative treatments in the osteoarthritis and non-osteoarthritis populations in Chapter 4. If the score performs well, we could then estimate the risk difference (excess risk) based on the established risk score. Unfortunately, its overall prediction performance was not good, as found in chapter 5. We then applied the frailty Cox model (conditional Cox model) based on the matched cohorts, controlling demographical variables, period effect, and coding variation at the practice level, adjusting lifestyles, body measurements, clinical measurements, and treatments to estimate the excess risk of CVD due to osteoarthritis. As the finding in Chapter 6, there was a significant excess risk of CVD for osteoarthritis, and higher in men, the elder and the deprived population. Importantly, the excess risk was also observed in the youngest age group (35-44 years). There could be potential unmeasured confounders, but the findings consistently suggest that clinical effectiveness, cost-effectiveness, and acceptability of potential preventive care strategies under the current screening criteria should be further addressed in the osteoarthritis population in the UK.

Introduction Retirement ages are rising in many countries due to population ageing and increasing life expectancy. It is unclear whether people in later working life (age ≥50) are able to work for longer due to health conditions and a lack of job opportunities. The work described in this thesis aimed to determine the average number of years that adults in England are expected to be healthy and in work from age 50, and investigate inequalities, projections until the year 2035, and association with health, lifestyle and workplace factors including osteoarthritis (OA) as an exemplar of a common long-term health condition. Methods Healthy Working Life Expectancy (HWLE) was identified through a systematic review as a potential indicator of population ableness to work for longer and operationalised as years spent healthy (no limiting long-standing illness) and in paid work ((self-)employment) from age 50. HWLE was estimated with discrete-time and continuous-time multistate models using IMaCh/R software, and longitudinal data from the English Longitudinal Study of Ageing and the North Staffordshire Osteoarthritis Project. HWLE projections were estimated using Health Survey for England data and official mortality rate statistics. Results HWLE at age 50 was 9.42 years (men: 10.94 years, women: 8.25 years). Subgroup analyses highlighted inequalities by socioeconomic status, and to an extent by occupation type and region. Having OA was associated with reduced HWLE, as was obesity, physical inactivity, pain interference, mental health problems, unsupportive work environments, and having no control at work. Projected from 2020 to 2035, life expectancy gains (men: 3.37 years; women: 2.46 years) exceeded HWLE gains (men: 0.38 years; women: 1.08 years). Conclusion HWLE in England is less than the years to the State Pension age. HWLE has potential to be used as a population indicator for work and support a joined-up approach between policymakers, employers and healthcare providers to extend working lives.

Despite significant advances in both understanding and technology, complications of surgical care have become a major cause of death and disability worldwide. A substan- tial proportion of these complications are deemed preventable. It has been hypothesised that preparing surgeons to operate may improve performance and, by extension, pa- tient outcomes. This thesis is concerned with three fundamental investigations into the effect of preparation (described as preoperative simulation) on surgical performance. First is an investigation into the current understanding of preoperative simulation, which involves a systematic review of the literature. Broad support for preoperative simulation is demonstrated, however, the studies suffer from methodological shortcom- ings and lack theoretical grounding. Building on this, a laparoscopic sequence learning task was developed to allow the investigation of preoperative simulation under controlled conditions. This was used in three controlled, randomised crossover trials. These experimental trials demonstrated that a simplified, relevant preoperative simulation can improve simulated laparoscopic performance. Exactly what form the preoperative simulation should take is deter- mined by the nature of the task/operation being performed and is likely to reflect how that procedure was learnt. Additionally, preoperative simulation can alter an opera- tors approach to completing a task, overriding a suboptimal but preferred method, to condition them to use a better method of completing the procedure. Finally, the natural experiment of repeating a procedure during an operative list was used to explore the effect of preoperative simulation in clinical practice. An inves- tigation of approximately a half million operations was conducted, which demonstrated that the order in which procedures are performed has a predictive relationship with operative duration (a surrogate for operative quality). This finding was relatively con- sistent across the thirty-five most common operations, and reinforced by the finding that switching procedures leads to significantly increased operative times. These investigations support the view that preoperative simulation improves surgi- cal performance.

The purpose of this thesis was to develop an in-depth understanding of motor control in surgery. This was achieved by applying current theories of sensorimotor learning and developing a novel experimental approach. A survey of expert opinion and a review of the existing literature identified several issues related to human performance and MIS. The approach of this thesis combined existing surgical training tools with state-of-the-art technology and adapted rigorous experimental psychology techniques (grounded in the principles of sensorimotor learning) within a controlled laboratory environment. Existing technology was incorporated into surgical scenarios via the Kinematic Assessment Tool - an experimentally validated, powerful and portable system capable of providing accurate and repeatable measures of visual-motor performance. The Kinematic Assessment Tool (KAT) was first established as an appropriate means of assessing visual-motor performance, subsequently the KAT was assessed as valid when assessing MIS performance. Following this, the system was used to investigate whether the principles of ‘structural learning’ could be applied to MIS. The final experiment investigated if there is any benefit of a standardised, repeatable laparoscopic warm-up to MIS performance. These experiments demonstrated that the KAT system combined with other existing technologies, can be used to investigate visual-motor performance. The results suggested that learning the control dynamics of the surgical instruments and variability in training is beneficial when presented with novel but similar tasks. These findings are consistent with structural learning theory. This thesis should inform current thinking on MIS training and performance and the future development of simulators with more emphasis on introducing variability within tasks during training. Further investigation of the role of structural learning in MIS is required.

Modern surgical training requires radical change with the advent of increasingly complex procedures, restricted working hours, and reduced ‘hands-on’ training in the operating theatre. Moreover, an increased focus on patient safety means there is a greater need to objectively measure proficiency in trainee surgeons. Indeed, the existing evidence suggests that surgical sensorimotor skill training is not adequate for modern surgery. This calls for new training methodologies which can increase the acquisition rate of sensorimotor skill. Haptic interventions offer one exciting possible avenue for enhancing surgical skills in a safe environment. Nevertheless, the best approach for implementing novel training methodologies involving haptic intervention within existing clinical training curricula has yet to be determined. This thesis set out to address this issue. In Chapter 2, the development of two novel tools which enable the implementation of bespoke visuohaptic environments within robust experimental protocols is described. Chapters 3 and 4 report the effects of intensive, long-term training on the acquisition of a compliance discrimination skill. The results indicate that active behaviour is intrinsically linked to compliance perception, and that long-term training can help to improve the ability of detecting compliance differences. Chapter 5 explores the effects of error augmentation and parameter space exploration on the learning of a complex novel task. The results indicate that error augmentation can help improve learning rate, and that physical workspace exploration may be a driver for motor learning. This research is a first step towards the design of objective haptic intervention strategies to help support the rapid acquisition of sensorimotor skill. The work has applications in clinical settings such as surgical training, dentistry and physical rehabilitation, as well as other areas such as sport.

Falls in older adults are a serious and increasing problem for the NHS. Due to their multifactorial causes falls are difficult to prevent but research suggests that assessment and early interventions of those at risk of falling can help reduce fall frequency and consequently alleviate the health service burden and improve quality of life for older adults. The overall objective of this work was to investigate postural stability in persons over the age of 65 years to understand why this age group are susceptible to falls. Three main research aims were pursued (i) establish the scale of the issue of falls in older adults; (ii) develop an assessment system to measure postural stability; (iii) determine the conditions that compromise postural stability and assess awareness of this compromised stability. Firstly the existing literature was reviewed and a large scale analysis of accident reports from a sample of UK care homes was carried out. The results showed that falls are a serious issue for older adults residing in care homes, but also that accident reports are not necessarily reliable and some institutions may underreport falls. Pilot work in the early stages of the research process developed an accurate and reliable system to measure levels of postural stability. A Wii balance board was interfaced with a computer based kinematic assessment tool to measure postural stability whilst carrying out a variety of computerised secondary tasks. This assessment system was then used to fulfil the final research aim of investigating postural stability in older adults when loaded with various secondary tasks. Older adults’ postural stability was found to be compromised when undertaking a concurrent visuomotor task, but critically the results showed that this group were unaware of this compromise. The implications of these findings are discussed and further research directions are suggested.

A decrease in motor ability can have a profound impact on a person’s capacity to maintain independence. Motor skill levels decline with age and this can create difficulties for older adults as they attempt to maintain independent lives. The fact that people in today’s society are living for much longer means that robust methods for examining movement in older adults, must be developed. These methods will increase our understanding of how movement deteriorates with age and inform approaches to rehabilitation in cases where movement is lost (e.g. motor paresis after stroke). Accordingly, this doctoral research used sophisticated kinematic technology to create a series of computerised visuomotor tasks designed to achieve the following primary aims (i) to examine specific questions regarding age differences in motor performance; (ii) to create an experimental task to measure and infer potential causes of age-related changes in motor learning; and (iii) use the motor learning task to assess the outcomes of tDCS in healthy younger and older adults. A secondary aim was to produce tests that have the potential for use in rehabilitative settings, where more sensitive methods of assessment are required. Chapter 1 reviews previous research on the topics of ageing, motor control, and rehabilitation, and identifies needs for further empirical investigation. Age differences in motor performance are examined in the experimental work of Chapters 2 and 3, which suggests that older people compensate for motor decline by making spatial and temporal adjustments to their movements in order to meet task demands – a finding that generalised between two different motor tasks. Chapter 4 considers performance differences between the preferred and non-preferred hand, and includes findings of a tracing study where manual asymmetries were reduced in older adults. The problems that can arise when measuring differences between the hands are, however, highlighted in the experimental work of Chapter 5. The research in Chapters 6 and 7 focuses on motor learning. In Chapter 6 a motor sequence learning task is developed, which was used to examine the relationship between motor performance and learning. This task paradigm was used again in Chapter 7, which begins by reviewing previous studies that have applied Transcranial Direct Current Stimulation (tDCS) to modify movement in healthy people and in stroke populations, and ends with two experiments that found no beneficial effects of tDCS on motor sequence learning in younger and older adults. Finally, Chapter 8 summarises the findings of each experimental chapter and considers future applications of the motor tasks designed throughout this doctoral work.