The declaration of COVID-19 as a global pandemic in March resulted in a rapid decrease in step counts worldwide, including in the United States, according to a new study by researchers at UC San Francisco.
A review of more than 19 million daily step count measurements taken by smartphone users worldwide found a wide range of variance, with some regions dropping nearly 50 percent in the month after the World Health Organization’s March 11 declaration. During that time, regional and national governments advocated for social distancing measures, with varying degrees of enforcement, from simple recommendations to full lockdowns.
Daily step counts have been inversely correlated with overall mortality, reflecting the importance of physical activity in health.
“Governments and policymakers should be aware of the impact of social distancing measures on decreasing physical activity, since physical activity is an important determinant of health,” said lead author Geoffrey Tison, MD, MPH, a UCSF Health cardiologist and assistant professor of cardiology at UCSF. “They might also consider the use of step counts or other smart device-based proxies for social distancing adherence, as regional governments consider methods to encourage and monitor social distancing.”
In the study, published June 29, 2020, in the Annals of Internal Medicine, Tison and his colleagues reviewed data from Jan. 19 to June 1, 2020, of 455,404 users of the free Apple and Android smartphone app Argus, which tracks daily step counts. A total of 19,144,639 measurements were recorded from 187 countries, with user location provided by the smartphone IP address.
Within 10 days of the March 11 pandemic declaration, there was a 5.5 percent average decrease (287 steps) worldwide, growing to a 27.3 percent drop (1,432 steps) within 30 days. The researchers found a wide regional variation in the average step count change and in the timing and rate of that change.
For example, Italy declared a nationwide lockdown on March 9, 2020, and saw a maximum 48.7 percent decrease in steps within 30 days. Sweden, which took a notoriously lenient approach to social restrictions, had a maximum 6.9 percent decrease. The researchers saw a 15 percent step count decrease in Italy at five days, Spain at nine days, France at 12 days, India at 14 days, United States at 15 days, United Kingdom at 17 days, Australia at 19 days and Japan at 24 days.
Step count trends in samples of the 10 largest U.S. cities also varied widely. The biggest overall drop occurred in New York, followed by San Jose and Los Angeles. Dallas had the smallest decrease, followed by Phoenix, Houston and Chicago.
The researchers attribute the wide variation to changes in social distancing adherence, as well as socioeconomic inequalities among the geographic regions and disparities in the ability to use recreational physical activity.
“Countries that, to date, have had relatively low COVID-19 infection rates and therefore have not instituted lockdowns, such as South Korea, Taiwan and Japan, still have exhibited decreases in overall step count,” Tison said. “The within-region step count trends likely reflect a combination of changes both to physical activity and activities of daily living due to social distancing efforts.”