Investigating the relationship between active commuting and cardiovascular disease in the UK: Longitudinal and spatial analysis of four large datasets

It is well known that keeping active reduces our risk of cardiovascular disease (CVD), obesity, high blood pressure and other health problems. However over the past few decades British lifestyles have become increasingly sedentary, with two thirds of us taking insufficient exercise. Globally, physical inactivity has become the fourth leading risk factor for premature death. Active commuting (walking or cycling to work) has been recommended by experts as a practical way of building more exercise into the daily routine. However, more research is needed. The precise ways in which active commuting affects cardiovascular health are not understood, and many important questions remain unanswered. I hope to embark on a three-year Medical Research Council funded programme at the London School of Hygiene and Tropical Medicine, to find out whether active commuting is good for our health.

The research will focus not just on walking and cycling trips, but on public transport too. Commuting by train, tube or bus usually involves a walk to the station, and standing when the service is busy also requires some physical exertion. Users of these active and public transport modes will be compared with people who commute by private transport (e.g. car, taxi or motorbike), which is usually more sedentary. The core objective of the project will be to investigate whether active commuters have better cardiovascular health than non-active commuters. This includes the biological antecedents of cardiovascular disease (such as obesity and high blood pressure) as well as more concrete outcomes such as heart disease diagnoses and CVD-related deaths. Factors such as disability, job type, and geographical location will be taken into account to ensure that any health differences observed cannot be explained away by these other elements. Furthermore, the statistical techniques and data sources used will allow the researcher to find out whether active commuting actually causes differences in health between active and non-active commuters.

This type of research is made possible by the UK's rich longitudinal data resources, three of which will be used in this project: the Office for National Statistics Longitudinal Study, the UK Household Longitudinal Study, and UK Biobank (middle-aged individuals only). These are large studies which follow tens or hundreds of thousands of individuals over time, inviting the same people to provide information on a number of occasions through their lives. In addition, data from a smaller, more focussed longitudinal study of young people and their families will also be used. The ORiEL (Olympic Regeneration in East London) study follows around 3000 teenagers, inviting them to provide survey data and have their height and weight measured on three occasions during their adolescence. All of the teenagers live and study in East London and characteristics of the urban environment through which they commute to school have been measured and classified. Using the ORiEL data, the research project will investigate whether properties of the areas travelled through affect whether the young people walk to school, cycle, take the bus or get a lift.

In summary, this project will answer a number of key questions about the health effects of active commuting. It will show whether active commuting is important for young people or middle-aged people, so that public health messages can be targeted at the most crucial age-group. It will show whether environmental factors such as pavements, crime and dedicated cycle routes actually increase the use of active travel modes. It will provide a long-range perspective by describing trends in active commuting over the past 4 decades and show whether long-term active travel can reduce CVD mortality risk. It will also show which particular points on the CVD 'causal pathway' are most influenced by active commuting: Weight? Fitness? Blood pressure? Or heart disease itself?

AIM: To produce a body of work investigating the causal relationship between active commuting (AC) and cardiovascular disease (CVD) outcomes through the lifecourse, using longitudinal and spatial approaches to the analysis of 4 large secondary datasets to unpack causality and process and situate the individual in their environmental and temporal context.

OBJECTIVES: (1) To describe the prevalence and patterning of AC modes through time and across the lifecourse. (2) To determine whether a robust, independent association exists between AC and a range health outcomes on the CVD pathway. (3) To determine the direction of causality in these relationships and to explore causal pathways. (4) To investigate the ways in which socioeconomic and physical characteristics of the urban environment affect commuting mode choice and modify the effects of AC on BMI.

METHODOLOGY: Outcomes of interest can broadly be split into 3 categories, reflecting their position on the causal pathway: (i) Biological antecedents of CVD; (ii) Diagnosed CVD-related conditions; (iii) CVD mortality. The exposure will be operationalised as a variable with three ordered categories of transport: Active; Public; Private. Four large longitudinal datasets will be exploited to illuminate distinct dimensions of the relationship between AC and CVD: (i) The ONS Longitudinal Study (ONS-LS); (ii) The UK Household Longitudinal Study (UKHLS); (iii) UK Biobank; (iv) The Olympic Regeneration in East London study (ORiEL). Complementary analyses of these 4 datasets will provide a comprehensive picture of the ways in which active commuting affects cardiovascular health in adults and young people in the UK. Analytical approaches will include longitudinal multilevel modelling, structural equation modelling and spatially explicit methods.

This combination of longitudinal and spatial epidemiological approaches will provide a novel view of the relationship between AC and CVD, and yield key recommendations for policy.

The proposed research will be of great interest to wide range of users spanning many sectors.
Academic researchers within the fields of epidemiology and public health will benefit from the contributions this work will make to the evidence base and the methodological insights which will be gained. This work will appeal to a wide academic audience in the UK and internationally. It will be of interest to the multidisciplinary range of researchers who use the population-level survey data which will be employed in this project.

The findings of the proposed research will benefit a number of public sector organisations. The findings will be directly relevant to the Department of Health, and could be used to promote policies which improve the nation's cardiovascular health. The Department for Transport will be another key user of the research findings. Promoting the infrastructure which could support and encourage active commuting is within this department's remit, and strong evidence to show that such infrastructural improvements would improve health would be of great impact. In addition, the results could also be of interest to the Department of Energy and Climate Change. Although this department would be primarily concerned with the environmental benefits of promoting active commuting (such as lowered greenhouse gas emissions and reduced air pollution), they would also potentially be interested in evidence which shows that active commuting has a wide range of benefits, including for health.

Other national bodies such as Public Health England would be able to use research outputs on the health effects of active commuting. Part of their remit is to set the agenda for priorities in public health policy, and persuasive evidence on the positive health effects of active commuting could be fed into policy at this level. At a regional level, Local Authorities would be key users of the proposed research as their remits include both urban planning and public health. Bodies such as the Greater London Authority would also be key users for these reasons. Decisions on the remodelling of urban environments should be made with a view to increasing the potential for safe walking and cycling. Persuasive evidence on the benefits of these activities for public health would be of great importance for Local Authorities.

It will be important to engage businesses with the findings of the research. If the research indicates a robust causal link between active commuting and cardiovascular health, then it is in the interests of businesses and workplaces to initiate schemes to encourage active commuting, and to ensure no barriers exist (such as inadequate cycle storage). For similar reasons, schools, colleges and universities would be potential users of this research. Equipped with evidence of its effects on obesity and other outcomes, schools could expand and increase efforts to encourage walking or cycling to school, perhaps through cycling proficiency programmes, advocating to the local authority for changes to road and pavement layouts, or educational sessions with young people and their parents to promote the health benefits of active commuting.