UNIVERSITY PARK, Pa. — Staying home and limiting local travel, supporting access to primary care, and limiting contacts in contagion hubs — including hospitals, schools, and workplaces — are strategies that might help reduce COVID-19-related deaths, according to new research. The research team, by statisticians at Penn State, the Sant’Anna School of Advanced Studies in Pisa, Italy, and Université Laval in Quebec, Canada, used novel statistical approaches to compare the first wave of the epidemic across 20 regions in Italy and identify factors that contributed to mortality.
“The first wave of the COVID-19 epidemic took very different paths in different regions, with some areas being hit especially hard while others fared much better,” said Francesca Chiaromonte, leader of the research team, who is a professor of statistics and the holder of the Lloyd and Dorothy Foehr Huck Chair in Statistics for the Life Sciences at Penn State, and the scientific coordinator of the EMbeDS department of excellence at the Sant’Anna School. “We wanted to understand why some regions were hit so much harder than others, so we used both vetted and newly developed techniques in a field of statistics called functional data analysis to compare how the first wave progressed in different regions in Italy.”
Rather than focusing on models for predicting epidemic trajectories, the study used functional data analysis techniques to gather information from the shapes of mortality curves over time, providing a sensitive way to capture associations and patterns from data. The researchers compared mortality curves during the first wave of the epidemic across 20 regions in Italy. After clustering and aligning the curves, to characterize their shapes and account for outbreaks beginning on different dates, the researchers could evaluate factors that might contribute to their differences. Their results appear Aug. 30 in the journal Scientific Reports.
The researchers found that local mobility — how much people moved around their local areas — was strongly associated with COVID mortality. Specifically, they used data from Google’s “grocery and pharmacy” category, which reflects mobility linked to acquiring necessities such as food and medicine. During a national lock-down which started in March 2020, these mobility levels dropped drastically in Italy, roughly by 30% just in the first week of lockdown and then further by as much as 60% during weekdays and almost 100% during weekends in March and April.
“Early on in the epidemic, there were a lot of questions about whether mobility restrictions would really work; our results add to the mounting evidence that they do,” said Chiaromonte. “We see the effect with a lag, but when people reduced their mobility, we saw fewer COVID-related deaths. And we aren’t the only ones to document this, so when we’re told to stay home as a mitigation measure, we should stay home!”