Using volunteered geographic information to assess mobility in the COVID-19 pandemic context: cross-city time series analysis of 41 cities in 22 countries from March 2nd to 26th 2020

Abstract

Background: Restricting mobility is a central aim for lowering contact rates and preventing COVID-19 transmission. Yet the impact on mobility of different policies of restriction is not well-understood.Methods: Trends were evaluated using Citymapper’s mobility index covering 41 cities worldwide between 2nd and 26th March 2020, expressed as percentages of typical usage periods from 0% as the lowest and 100% as normal. China and India were not covered. Multivariate fixed effects models were used to estimate the association of policies restricting movement on mobility before and after their introduction. Policy restrictions were assessed using the Oxford COVID-19 Government Response Stringency Index as well as measures coding the timing and degree of school and workplace closures, transport restrictions, and cancellation of mass gatherings. Results: Mobility declined in all major cities throughout March. Larger declines were seen in European than Asian cities. The COVID-19 Government Response Stringency Index was strongly associated with declines in mobility (r = -0.75, p<0.001). After adjusting for time-trends, we observed that implementing a mobility restriction to the recommended level was associated with a decline of mobility of 10.0% for school closures (95% CI: 4.36% to 15.7%), 15.0% for workplace closures (95% CI: 10.2% to 19.8%), 7.09% for cancelling public events (95% CI: 1.98% to 12.2%), 18.0% for closing public transport (95% CI: 6.74% to 29.2%), 13.3% for restricting internal movements (95% CI: 8.85% to 17.8%) and 5.30% for international travel controls (95% CI: 1.69 to 8.90). In contrast, as expected, there was no association between population mobility changes and fiscal or monetary measures or emergency healthcare investment.Conclusions: Understanding the effect of public policy on mobility is crucial to slowing and reducing COVID-19 transmission. By using Citymapper’s mobility index, this work provides the first evidence about trends in mobility and the impacts of different policy interventions, suggesting that closure of public transport, workplaces and schools are particularly impactful.

Lockdown stringency and paediatric self-harm presentations during COVID-19 pandemic: retrospective cohort study

“…Recent studies suggested that mobility in the general public reduced with increase in stringency. 17 School closure was found to be associated particularly with time staying at home. While youths who self-harm may avoid presentations at hospitals out of fear of contracting and spreading the disease or concerns of being labelled as an ‘attention-seeker’, 11 stringent government restrictions might have inadvertently further discouraged help-seeking behaviour in those who were in need.…”

“…Studies across the globe have suggested that stringency effectively reduced mobility in the community. 17 Referrals to child and adolescent mental health services displayed various patterns in different periods of the lockdown. 18 It is possible that the unintended consequences of lockdown varied with the magnitude of lockdown stringency, creating barriers to emergency presentations.…”