Anecdotal evidence of “pandemic fatigue” — defined by the World Health Organization as “a lack of motivation to follow recommended COVID-19 protection behaviors” — has been reported and shared almost as long as physical distancing guidelines have been around to fight the spread of the disease. Now, a research team, including a Johns Hopkins medical student, has the data to prove it.

The researchers analyzed almost nine months of survey responses to the University of Southern California’s Understanding America Study, during which, twice each month, nearly 8,000 people across the United States were asked if they were practicing nonpharmaceutical interventions (NPIs), including physical distancing, frequent handwashing and wearing a mask.

The researchers used the data to develop a national NPI adherence index, detailed in a research letter published Jan. 22, 2021, in the Journal of the American Medical Association. The index, they report, started at 70 (out of 100, which would be total adherence) in early April 2020, dropped and plateaued in the high 50s in June, and increased slightly to 60 by Thanksgiving. The decrease was consistent across every region in the country.

“The plateau we see for overall NPI adherence in the results likely reflects some stability in the risk perception of different activities,” says study lead author Matthew Crane, a second-year medical student at the Johns Hopkins University School of Medicine. “It’s good to see adherence isn’t continuing to drop at the initial rate because that would be terrible. But it’s also disconcerting that protective behaviors overall have become relatively stable no matter what the national state of COVID-19 prevalence is. Given new, more transmissible variants of the virus that are arising globally, we really might need greater adherence to keep people safe.”

The NPIs that had the largest decreases were remaining at home except for essential activities and exercise (79.6% of respondents did so in April 2020 compared with 41.1% by November), having no close contact with non-household members (63.5% decreased to 37.8%), not having visitors at their homes (80.3% decreased to 57.6%) and avoiding eating at restaurants (87.3% decreased to 65.8%).

“I was surprised [NPI adherence] wasn’t more responsive to surges in COVID-19 cases,” Crane says. “I thought it would fluctuate based on headlines and public health advisories.”

The biggest increase was in mask wearing, which went from 39.2% to 88.6%. But Crane notes the survey asks if respondents have done or not done a specific action in the last seven days. That means a person might have worn a mask because it was required to visit a grocery store or another public space but was still opposed in principle to the rule.

“It might not be an endorsement of mask wearing,” Crane says.

Crane hopes to continue to track NPI adherence and break down the survey data further, providing more insight for public health professionals to create targeted messaging to change behaviors.

“Until vaccines are very widely distributed, these protective behaviors will be the cornerstone of our national response. It’s really what is going to get us through this, the NPIs,” he says.

Crane is available for interviews.