COLUMBUS, Ohio - Getting more nutritious meals on the tables of low-income Americans could depend on the hours the stores in their neighborhoods keep.

Stores likely to sell fresh produce aren't open as long in areas with more socioeconomic struggles, and that problem is more pronounced in neighborhoods where many African Americans live, new research from The Ohio State University has found.

In affluent neighborhoods, 24-7 access to a wide array of foods is far more common.

"Let's say you're stringing together a few jobs and you get off work at 10 and your market closes at 8. It's a big problem," said researcher Jill Clark, an assistant professor in Ohio State's John Glenn College of Public Affairs.

"It's just another burden that we are placing on families that already have so many burdens."

Advocates and policymakers have invested extensively in working to eliminate food deserts - areas with limited or no large grocery stores or supercenters.

But they fall short when they look only at proximity, density and diversity of food retail stores and ignore the little-discussed problem of operating hours, Clark said.

Future policy changes - including those that pertain to the nation's Supplemental Nutrition Assistance Program - should include opportunities to help meet consumers' needs, such as extending store hours or ensuring transportation is available to get consumers to stores that are open, Clark said.

She and Xiang Chen, now of Arkansas Tech University, found that time-related obstacles were greatest in lower-income African-American neighborhoods where people also are more likely to face challenges including single parenthood and work schedules that make it difficult to shop. Their work appeared this month in the journal The Professional Geographer.

"It's not just people getting to stores. It's whether or not there are lights on when you get to the store," Clark said. "Time is a resource that we should not discount."

The researchers looked at store hours in Franklin County, Ohio, home of Columbus, the state's capital. Federal estimates of supermarket access put Franklin County near the national average. An estimated 23.7 percent of the county's 1.2 million residents have low access, defined as living more than one mile from a supermarket in urban areas and more than 10 miles in rural areas.

The researchers created a three-dimensional mathematical model to better understand the locations and hours of 118 stores.

Overall, they found access lowest from 12:30 to 5:30 a.m. The peak of access was at around 11 a.m. and stores started to close around 7:30 p.m.

The researchers found that in neighborhoods that did have stores, an average of just 23 percent of people had good access based on both store location and hours.

Calculations of access that took time into account climbed alongside measures of socioeconomic well-being. Store hours were longer where incomes were higher, unemployment was lower, more people had cars, a greater percentage of the population had graduated high school and where the population was mostly white.

Those with poor access may turn to fast food and other unhealthful options, such as gas station offerings, the researchers wrote.

On a broader scale, this research contributes to a better understanding of the fact that food access isn't just about proximity or cost or any single factor, Clark said.

"Access is complex. Can you get there when it's open? When you get there can you afford it? If you get there and you can afford it, is it healthy?"

That presents policymakers, from community activists to the federal government, with opportunities to tailor their efforts to the needs of the neighborhoods they're trying to help, Clark said.