Role of intensity, duration and pattern of accelerometer-assessed physical activity for cardiometabolic health – ActivHealth

Promotion of physical activity has been an integral part of public health policy but our lifestyles are increasingly sedentary and the epidemic of obesity and diabetes continues to grow. Current guidelines recommend 30 minutes per day, 5 days a week (or 2.5 hours per week) of moderate-to-vigorous physical activity but most people do not meet these recommendations, particularly at older ages. In practice, most of our waking time is spent in sedentary and light activities for which there are no clear recommendations. This is mainly due to imprecise measurement of these behaviours rather than robust evidence showing them not to be important for health. The correlation between self-reported and objective measures of physical activity is modest and there is increasing evidence of differences in association with health of objectively-assessed and questionnaire data on physical activity. In addition, questionnaire data are not well suited to assess sedentary and light activities, they also do not capture the manner in which physical activity accumulates over the day. Thus, research based on better measures of physical activity including sedentary behaviour is needed urgently in order to characterize the natural combination, or the “posology”, of everyday physical activities that benefit health.
This project focuses on cardiometabolic health due to the importance of physical activity for these outcomes and their population burden. We aim to identify core dimensions of everyday physical activity and sedentary behaviour that shape cardiometabolic health, defined using cardiometabolic risk markers (blood pressure, cholesterol, insulin, glucose, arterial stiffness) and hard cardiometabolic endpoints (stroke, heart disease, diabetes). Our emphasis will be on:
1) Assessing the importance of sedentary and light activities,
2) Determining activity intensity thresholds in relation to cardiometabolic health,
3) Examining the importance of breaks in sedentary activities independently from total sedentary time,
4) Identifying optimal physical activity patterns based on intensity, duration, context, and timing of physical activity.
The project will be based on data from 4000 participants of the Whitehall II cohort aged between 60 and 83 years that include both objective measures of physical activity (7-day accelerometer data) and prospective measures on cardiometabolic health over 7 years. The innovation of the project lies in the use of a new generation of accelerometers assessing moment-by-moment (“raw”) acceleration (over 200 data points per second per participant). The analysis of these data will allow us to evaluate the importance of intensity, bout duration, and pattern of physical activity for cardiometabolic health. There are considerable methodological challenges in the construction of these parameters from raw data and we propose to make our work available to the scientific community using open access R package in order to encourage future studies to assess physical and sedentary activities objectively using such devices. In addition, this will allow replication of our findings in other studies in order to test their generalizability.
Findings from this project will provide new insights into the aspects of everyday activities (intensity, bout length, pattern) that ought to be promoted for cardiometabolic health. If replicable in other studies, we hope to generate evidence to help inform future targeted longer term interventions to assess the causality of the association in order to refine current physical activity guidelines. In clinical practice, our findings could be used to improve the prognosis of high risk individuals and provide them precise and easily implementable recommendations to reduce their cardiometabolic risk. Minor, readily adoptable changes in everyday routine are more likely to be sustainable in the long-term and even if the benefits are small, the overall impact at the population level will be considerable.