Quantifying population levels of physical activity in Africa using wearable sensors: implications for global physical activity surveillance

We are all Africans. Local availability of food likely caused the first Homo sapiens to migrate out of Africa some 50 000–70 000 years ago and populate the rest of the world. Throughout human history, our behaviour has been governed by our planet’s rotation and revolution around the sun, particularly from the time of the agricultural revolution about 12 000 years ago when the first calendars start to appear, guiding agricultural activities. In the modern age of globalisation, however, food supply is relatively stable over the course of the year in many countries, but the need for primary food production, local weather conditions and availability of daylight continue to impact the activity of populations around the globe to varying degrees. Physical activity has consistently been shown to be associated with several health benefits, but global surveillance data suggest that on average one in four adults are insufficiently active, with populations living in low- and middle-income countries being far more active than those living in high-income countries.1 The WHO Global Action Plan for Physical Activity aims to reduce the prevalence of insufficient activity by 10% in 2025 and by 15% in 2030.2 The key to monitoring progress towards these targets is a robust surveillance system. Currently, systematic global monitoring of physical activity is based on self-report methods, and while it is important for continuity of information that this element of surveillance is continued, there are clear advantages to supplementing self-report data with device-measured physical activity. Accelerometers and heart rate monitors provide objective and much more fine-grained information about habitual physical activity patterns, in particular with respect to intensity of activity, and avoid many of the issues with self-report, such as recall bias and social desirability bias. However, it is still relatively uncommon for devices to be used in epidemiological studies in Africa. Pratt and …