key: cord-0917906-onr61nru
authors: Zipursky, Jonathan S.; Redelmeier, Donald A.
title: Association Between Driving in the Summer and COVID-19 Mortality in the Autumn
date: 2021-08-06
journal: J Gen Intern Med
DOI: 10.1007/s11606-021-07074-z
sha: 9018549e085c244caee9c41a196b0aaf0cc696c8
doc_id: 917906
cord_uid: onr61nru

nan

Behavioral interventions can be successful methods to control a pandemic. 1 In response to COVID-19, onethird of the world's nations instituted formal lockdowns. 1 We previously showed that nations that reduced mobility experienced less COVID-19 mortality during the early months of the pandemic. 2 Severe restrictions are not sustainable; however, premature loosening of restrictions can lead to a COVID-19 resurgence. 1 In particular, many nations eased mobility restrictions in the summer of 2020. Herein, we reassessed the association between mobility and COVID-19 mortality by examining changes of driving distances in the summer and COVID-19 mortality in the autumn.

We examined the same original 36 nations from our previous study of the first wave of the COVID-19 pandemic. 2 We calculated the mean change in mobility from baseline (driving distances on January 13, 2020) for each nation during the summer (June through August 2020) using Apple Mobility Trends. 3 For each nation, we collected data on COVID-19 mortality during the autumn (September through November 2020) using Our World in Data. 4 Excess mortality was estimated by dividing the total number of COVID-19 deaths by the total population size of each nation. In a secondary analysis, we assessed the association between changes in driving distance and changes in COVID-19 cases. As in earlier studies 2 , we used the Spearman rank correlation coefficient to test the association between the reduction in driving and subsequent changes in COVID-19 mortality rate in each nation.

The majority of nations (n=26, 72%) demonstrated increased driving distances in the summer compared to their own earlier baseline. In the autumn, we also found significant variation in COVID-19 mortality rates. For example, the Czech Republic had the highest mortality (73.5 per 100,000) and Singapore had the lowest mortality (0.03 per 100,000). As hypothesized ( Fig. 1 ), we observed a significant association between increased driving distances and higher COVID-19 mortality (r=0.35, p=0.036). In addition, we observed a significant association between increased driving and higher COVID-19 cases (r=0.48, p=0.003) (Fig. 2) . These trends suggested that, for the USA, a 10% increase in driving distances might have contributed to an additional 4,100 deaths and 459,000 cases.

Sensitivity analyses using shorter and longer time periods for assessing changes in mean driving distances found similar correlations of increased driving with increased COVID-19 mortality. In an additional sensitivity analysis restricted to 19 of the nations deemed by the WHO in the top public health systems, we observed consistent findings (r=0.37). 5 In a further analysis restricted to the 21 nations with data on public transit, we found no significant correlation between increased use of public transit and increased COVID-19 mortality (r=0.07).

We found that nations exhibiting increased driving in the summer experienced more COVID-19 mortality in the autumn. These findings support previous work suggesting that communities with greater adherence to mobility restrictions experienced lower COVID-19 mortality. 2,6 However, our findings are unlikely causal because population mobility may be one of several factors associated with COVID-19 mortality.

The stronger association with COVID-19 incidence rather than COVID-19 mortality suggests community spread of infection may be related to human mobility. This differential also highlights the potential greater importance of demographics, healthcare capacity, and other factors for influencing Figure 1 Association between driving distances and COVID-19 mortality. Nations to the right of zero show increased driving and nations to the left show decreased driving. Y-axis denotes total additional deaths from COVID in autumn for each nation adjusted for total population size. Correlation coefficient (r) based on the Spearman rank statistic. Overall data show a significant association between increased driving and increased mortality.

COVID-19 case fatality. As well, more research on countries such as Norway is needed to better understand how a few outlier nations sustained low COVID-19 mortality despite having substantial increases in driving distances in the summer. One limitation of our study is the uncertainty around whether some nations loosened restrictions in response to excellent initial control of the virus. Such reverse causality is possible, since our analysis assessed outcomes three months after assessment of driving patterns without adjustment for other potential confounders. As well, we were unable to account for whether people were traveling by car instead of plane because we lacked data on alternate modes of transport. Additional limitations include the inability to determine vehicle occupancy, the purpose of individual trips, or whether the driving was for private or commercial purposes.

In conclusion, our data further support the potential for controlling community spread of a pandemic through Figure 2 Association between driving distances and COVID-19 cases. Countries to the right of zero show increased driving and nations to the left show decreased driving. Y-axis denotes total additional cases from COVID in autumn for each nation adjusted for total population size. Correlation coefficient (r) based on the Spearman rank statistic. Overall data show a significant association between increased driving and increased COVID-19 case counts.

mobility restrictions in addition to other behavioral interventions. 

Lessons learnt from easing COVID-19 restrictions: an analysis of countries and regions in Asia Pacific and Europe

Mobility and Mortality During the COVID-19 Pandemic

COVID-19) -the data

Measuring Overall Health System Performance for 191 Countries

Impact of climate and public health interventions on the COVID-19 pandemic: a prospective cohort study