There are two options for buying groceries near Cathy’s home in West Oakland, California: a tiny and sometimes expensive co-op and a 99 cent store. Although she loves the co-op, they’re only open until 8 p.m. during the week and 4 p.m. on weekends. The 99 cent store is open until 9 p.m., but its produce and dairy offerings are limited and often teeter on the edge of their expiration dates.

“I have thoughts about the 99 cent store, but overall, without them and their small supply of vegetables, it would be very difficult to live here,” says Cathy, a 44-year-old student who preferred not to use her last name. She spends a half-hour on public transit traveling to other medium to large-sized grocery stores, not counting the time spent waiting at the bus stop and/or train stations. “A store that closes at 10 p.m. would be lovely,” she says.

A new study from geographers at Ohio State University (OSU) and Arkansas Tech University focuses precisely on the type of dilemma many in Cathy’s neighborhood face: reduced store hours, a previously overlooked piece of the complex puzzle that is the modern “food desert.” According to the U.S. Department of Agriculture (USDA), these are areas where residents experience what’s called “low access” to supermarkets, which is defined as living 1 mile away from a large grocery store in urban areas and more than 10 miles from one in rural areas.

The researchers found that hour restrictions can be just as limiting as distance to the food source. They looked at the locations and hours of 118 stores in Franklyn County, the area surrounding Columbus, Ohio. They found that only 23 percent of the area’s 1.2 million residents had good food access when both their proximity to a store and store hours were considered.

“This is the first study that addresses something we’ve known for a long time about food procurement, particularly among low-income, full-time working mothers—that time is a resource,” says co-author Jill Clark, assistant professor in the John Glenn School of Public Affairs at OSU.

Katherine Clover, a 30-year-old writer who has lived in various neighborhoods of Detroit considered “food deserts” for eight years without a car, says the city’s unreliable bus system makes getting to better supermarkets in other neighborhoods before they close difficult.

“In all honestly, it’s a pain,” she says. “If you had asked me this question two years ago, I would have said it was no big deal, but now I have a 1 year old and having to jump through multiple hoops just to buy quinoa matters to me.”

Reduced store hours can contribute to poor health because it could result in residents turning to unhealthier fast food and convenience store options for core meals, the researchers say. If stores stayed open longer, it might help people with low access, particularly those who don’t own cars.