“You can have states right next door to each other, like Connecticut and New York, that have a totally different pattern but yet experienced the same wave,” Dr. Richardson said.
Cumulatively over 55 weeks, mortality rates were slightly higher for women in two states, Rhode Island and Massachusetts. In nine states, including Connecticut, the rates were roughly equal. And in the rest of the country, death rates were higher for men.
Sex differences in genes, hormones or immune responses are not likely to explain these differences, the researchers said.
“There would be no reason for biology to be that variable across time and space,” said Katharine Lee, a biological anthropologist and engineer at Washington University in St. Louis and an author of the new study.
But social and behavioral factors, the researchers said, could help explain many of these patterns.
For example, men are more likely to have jobs in transportation, factories, meatpacking plants, agriculture and construction — occupations with higher rates of Covid-19 exposure and fatalities. Men are also more likely to be incarcerated and to experience homelessness, increasing their risk of virus exposure.
Women are more likely than men to report hand washing, mask wearing and complying with social distancing restrictions, all of which may lower their risk of contracting the virus. And women are more likely to be vaccinated.
The researchers speculated that states with more public health restrictions might see reduced sex differences. In New York, which saw a significantly higher number of male deaths in the first six weeks of the pandemic, mortality rates evened out once restrictions were put in place. The observed differences in New York could also be partly explained by better data collection, as well as underreporting of deaths in long-term care facilities, where the majority of residents are women.