A Population Perspective on Physical Activity and Health

Regular physical activity reduces the risk of many chronic diseases. Consequently, the promotion of it and particular types (e.g. walking and cycling for travel), have become a priority for governments seeking to improve health and constrain rising demand on health services. Despite this many uncertainties persist. The aim of this thesis is to address two particular areas of uncertainty: a) the association of walking and cycling for travel with indices of health and well-being; b) and the extent to which increases in physical activity will reduce need for health and social care. The first part of my thesis consists of three studies that describe the health benefits associated with walking and cycling to work among working age adults. The first is a longitudinal study of the associations between maintenance of active commuting with sickness absence and well-being using the Commuting and Health in Cambridge dataset. The second, using the same dataset, describes the longitudinal associations between maintenance of active commuting and self-reported body mass index. Building on this, the third study using a large cohort study (the Fenland Study) with detailed characterisation of diet and physical activity (including objective measurement) describes the baseline associations between active commuting and objective measures of adiposity. The second part of my thesis describes the development of a combined microsimulation multi-state life table model that is used to characterise the effects of a population ‘shift’ in physical activity on the burden of six major diseases at the population-level. Specifically, it seeks to better describe the effect of increases in physical activity on healthcare need considering not just the effect of physical activity on disease incidence but also the effect on healthcare need arising from consequent survival to an older age (at which disease incidence is higher), and contrasts this with a method that does not make allowance for increased survival. The findings of this thesis provide evidence of the importance of walking or cycling to work in maintaining or improving the health and well-being of working age adults. It suggests that increases in physical activity, even after allowance for increased survival, are likely to reduce need for healthcare, although the reductions in need are less than might be assumed when allowance is not made for increased survival. Taken together this work provides a stronger empirical basis to inform public health practice. A stronger ‘health case’ for active travel can be made. The benefits of which should be communicated to individuals choosing how to travel as well as policy makers and others who can influence the determinants of active travel. It also provides a more realistic and nuanced understanding of how increases in physical activity may affect future healthcare need.Wellcome Trust clinical doctoral fellowship (WT103394