Regions where more young adults live with their parents have experienced significantly higher rates of COVID-19 deaths, according to a new study based on European and U.S. data.

The effect is far more pronounced in the U.S. than in Europe, researchers wrote in the study, which was published in the December 2020 edition of Economics & Human Biology. One additional percentage point of individuals aged 18 to 34 living with their parents in a given U.S. state was associated with a 11.8% increase in cumulative COVID-19 deaths 100 days after the virus reached that state. 

“I realized that there must be a family connection, because Italy and Spain were among the first countries that had a lot of people who were affected by the pandemic,” Shoshana Grossbard, an economist at San Diego State University and a co-author of the study, said in an interview. Grossbard wrote the paper alongside Ainoa Aparicio Fenoll from the University of Turin in Italy. The researchers attributed the astronomical death tolls in those two countries to high rates of young adults living with their parents, possibly due to close family ties fostered by Catholicism. 

As the coronavirus pandemic set in, millions of young people were laid off and universities switched to online learning, causing many to move back in with their parents. In the U.S., a Pew Research poll showed that 52% of 18- to 29-year-olds were living with their parents during the summer of 2020 — a 5% year-over-year increase and the first time that number was higher than 50% since the Great Depression. 

But Grossbard and Fenoll were not able to access comprehensive state-by-state and country-by-country demographic data for 2020; instead, they used 2018 figures. Fenoll told The Academic Times that using older figures actually may have led to more accurate results. 

“If we had used coresidence patterns in 2020 in our analysis, our results could have been artificially inflated because not only intergenerational coresidence may increase COVID deaths, but also the COVID crisis increases intergenerational coresidence,” Fenoll said. “From the methodological point of view, using coresidence patterns in 2018 gets us closer to the implications of intergenerational coresidence for COVID deaths.”   

Grossbard added that even though the number of young adults living with their parents rose significantly, “There is likely to be a high correlation between intergenerational coresidence rates in 2018 and 2020, so our results would not be so different if we had data for 2020.” 

The researchers used coronavirus death data from all 50 U.S. states and 29 European countries from Feb. 15 to Aug. 3 of last year. 

Looking at all regions combined, the researchers found that one additional percentage point of young adults living with their parents was associated with 4% more deaths after 40 days, 3.5% more deaths after 60 days, 3.2% after 80 days and 3.1% after 100 days.

However, the association was much stronger in the U.S. than in Europe, where intergenerational coresidence did not have a statistically significant effect on deaths, the researchers said, noting that this disparity could be an area for further research. 

Examining coronavirus deaths at the U.S. state level is a novel approach, as other researchers have mostly opted to look at deaths only at the country level. 

Grossbard, who is originally from Belgium, said that many people in Europe and the U.S. don’t realize how much variances in lifestyles across states and regions can impact public health. For example, just 14.5% of young people in North Dakota live with their parents, compared to 33.9% in Hawaii and 46.25% in New Jersey. 

“Most Americans are not sufficiently aware of how deep the differences are across the states,” she said.  “They don’t understand how different it is to live in Louisiana versus New York … they’re really like different countries in many ways.” 

Though Grossbard is not a public health specialist, her work focuses on economics in relation to families and households, and she’s particularly interested in topics such as domestic violence and marriage laws. She also edits the journal Review of Economics of the Household, which she founded nearly two decades ago. 

Prior to the pandemic, Fenoll had published work about the economics of intergenerational coresidence in Grossbard’s journal. When the pandemic hit, Grossbard realized the potential to build on Fenoll’s research in relation to the coronavirus. 

“I contacted her and asked her, ‘Would you like to do a joint paper, where we’re going to explain mortality from COVID as a function of the differences between the countries in Europe that she already had data for?’” said Grossbard. 

The paper, titled “Intergenerational residence patterns and Covid-19 fatalities in the EU and the US,” was published in the December 2020 issue of Economics & Human Biology.

The co-authors were Shoshana Grossbard of San Diego State and Ainoa Aparicio Fenoll of the University of Turin. Fenoll was lead author.