US researchers have used people’s smartphones to amass large-scale physical activity data and measure activity patterns across populations worldwide.
By looking at accelerometry data recorded on the phones, the researchers could assess physical activity levels among 717,527 people and compare it across 111 countries.
Study author Scott Delp (Stanford University) says the research has provided data from more countries and many more people than previous health surveys have. It also tracks people’s activity on an ongoing basis: “This opens the door to new ways of doing science at a much larger scale than we have been able to do before.”
As reported in Nature, the average number of daily steps taken worldwide was 4,961. Hong Kong was in the lead, averaging at 6,880 daily steps and Indonesia ranked the lowest with an average of just 3,513 daily steps.
The authors say the findings provide important insights that could be used to develop health improvement strategies. For example, the average number of steps seemed to be a weaker predictor of obesity prevalence than “activity inequality” (i.e. the difference in activity between the least and most active people). One of the smallest gaps between high and low physical activity was seen for Sweden, which also had one of the lowest rates of obesity, whereas in the US, where the activity inequality was higher, obesity rates were also higher.
Interestingly, the extent of activity inequality seemed to be driven largely by gender differences in activity. In Japan, where inequality was low, men and women had similar levels of physical activity. By contrast, in the US and Saudi Arabia, where inequality was high, it was women who had the lower activity levels.
Co-author Jure Leskovec explains: “When activity inequality is greatest, women’s activity is reduced much more dramatically than men’s activity, and thus the negative connections to obesity can affect women more greatly.”
The gender gap in activity and activity inequality were also influenced by environmental aspects such as the “walkability” of a city. In cities where it was easier to walk around, daily and weekly activity were greater, irrespective of age, gender and BMI groups, with the greatest increases seen among females.
The data showed that New York and San Francisco were pedestrian friendly and easier for people to walk around, whereas Houston and Memphis had “low walkability,” meaning people preferred to use a car.
The authors say this could be useful in helping to design towns and cities in a way that promotes greater physical activity.
“Our findings have implications for global public health policy and urban planning and highlight the role of activity inequality and the built environment in improving physical activity and health,” they conclude.