Physical Activity Epidemiology

The overall aim of this programme is to understand the detailed relationships between physical activity and disease, particularly obesity and metabolic disorders. Further, we are also examining how the environment, early life factors such as birth weight, and genes affect the associations between physical activity with obesity and metabolic disorders. We have lead the development and evaluation of an objective method based on the combined measurement of heart rate and body movement for measuring physical activity precisely in free living individuals. This technique is now implemented in our epidemiological studies and in collaboration with researchers in UK and abroad. We will use this method in future studies. We seek to understand population levels of physical activity and how activity levels might change by time and between sub-groups of the population. We have shown that physical activity is positively associated with metabolic disorders in both children and adults and this association is independent of aerobic fitness. This has important public health implications as it may be more feasible to encourage the population to increase their levels of activity rather than improving aerobic fitness which is likely to include more vigorous exercise. We will seek to further examine the importance of physical activity in the causation of disease and how these associations differ between sub groups of the population. For example, we will include precise measurements of physical activity and body composition from early age in various birth cohorts. Finally, we will examine the heritability of activity in twin studies and the genetic determinants of activity in large scale observational studies.

Physical activity is assumed to be a key determinant of both obesity and metabolic diseases. However, the detail of this association is not fully clear. A major reason for this is that physical activity is typically poorly measured in epidemiological studies. The overall goal is to understand how physical activity and sedentary behaviour affect the health of people across the lifespan. AIMS The physical activity programme is divided into three different areas of research and the overall aims of the each of the areas are; 1. MEASUREMENT OF PHYSICAL ACTIVITY; Develop and evaluate methods for assessing physical activity in epidemiological studies 2. PHYSICAL ACTIVITY, SEDENTARY BEHAVIOUR AND CAUSATION OF DISEASE; Understand the role of physical activity and sedentary behaviour in the causation of obesity, diabetes and other chronic diseases 3. BIOLOGICAL DETERMINANTS OF PHYSICAL ACTIVITY AND SEDENTARY BEHAVIOUR; Understand the determinants, specifically the biological determinants (genotype and early life factors), of physical activity and sedentary behaviour and how these variables may modify the association between physical activity, obesity and related metabolic disorders MEASUREMENTS OF PHYSICAL ACTIVITY Measurement precision of exposure variables such as physical activity is key in epidemiological research. We are evaluating various objective methods for assessing physical activity including a combined heart rate and movement sensor (the Actiheart) for use in large-scale epidemiological studies. Our results show that this method is more accurate than other comparable objective activity assessment methods in both children and adults for assessing physical activity energy expenditure. However, these studies are restricted to confined settings and we are currently undertaking free living validation work using doubly labelled water (DLW) as the criterion method in UK children and adults. Preliminary data from these studies suggest that the combined heart rate and movement sensing is valid for estimating free living PAEE without any systematic error. It is, however unknown whether the validity of combined heart rate and movement sensing and other movement sensors is influenced by age, culture, climate and other environmental factors. We have therefore initiated studies to examine how different environmental conditions may affect the validity of this method. The next generation of objective measurement instruments will have the possibility to detect different types of activities performed. We have initiated work on developing a high frequency (80 Hz) sampling movement sensor in collaboration with industry for activity type classification. Our work on self-reported physical activity include the development self-report physical activity instruments specifically fit for purpose with the aim to establish a portfolio of questionnaires developed for different age groups, time frames, and assessing different domains of activity. This includes testing the reliability and validity of the European Prospective Investigation into Cancer (EPIC) physical activity questionnaire across 10 countries in Europe. PHYSICAL ACTIVITY IN THE CAUSATION OF DISEASE We aim to examine the complex interrelationships between sedentary behaviour and physical activity with morbidity, mortality and intermediate metabolic traits, throughout life. We aim to explore the direction of associations between physical activity, sedentary behaviour and health outcomes and how physical activity and sedentary behaviour may interact in relation to health. A long term goal is to understand how precisely measured physical activity and sedentary behaviour in childhood may influence on adult health. BIOLOGICAL DETERMINANTS OF PHYSICAL ACTIVITY Our overall aim is to understand the biological determinants of physical activity including birth weight, infancy and childhood growth, motor development and genotype and how these factors may modify the association between physical