Every year, the Robert Wood Johnson Foundation and the University of Wisconsin Population Health Institute give every county in Ohio a checkup.

For the fourth consecutive year, those institutions have ranked Delaware County as the state's healthiest county overall.

The annual County Health Rankings and Roadmaps report, which was released earlier this month, also listed Delaware County as No. 1 in the subcategories of health factors and health outcomes.

The category of health outcomes, according to the study, measures how long people live and how healthy they feel. The health-factors ranking tries to estimate the future health of a county's residents based on behavioral, economic and environmental factors.

Shelia Hiddleson, health commissioner of the Delaware General Health District, said the ranking will not lead to complacency for her agency or its partners throughout the county.

"It is always good news, but we don't rest on our laurels because there are always areas to work on," she said.

Hiddleson pointed to the fact that the study ranks Delaware County's physical environment 54th out of 88 counties. The low ranking stems from the percentage of residents who commute more than 30 minutes alone and the comparatively high air pollution.

Hiddleson said the county's proximity to Columbus plays an outsized role in the physical-environment ranking.

She said area agencies have taken steps to allow residents to share commutes to Franklin County and back. For instance, she said the Delaware Area Transit Agency has bus routes that tie into Central Ohio Transit Authority routes.

Hiddleson said it's up to county residents to take advantage of the opportunity.

"We're very fortunate that most of our residents are employed and can afford transportation," she said about the relatively high percentage of residents who make long, solo commutes.

Even in areas in which the county achieved impressive ratings, Hiddleson sees room for improvement.

Fewer than 15 percent of adults in the county smoke tobacco -- the lowest rate in the state.

Hiddleson said the district and its partners are working with schools throughout the county to help educate students about the dangers of tobacco products in an attempt to make that percentage fall even lower in the future.

"We do know that if people don't start smoking early, they're less likely to be a lifelong smoker," she said.

Although the practice is not measured in the rankings, Hiddleson said district officials also are working to educate students about vaping. She said some students may view using electronic cigarettes as a harmless alternative to smoking, which Hiddleson rejects.

"Putting any foreign substance in your lungs is not a good thing," she said.

Hiddleson said she ultimately credits the county's No. 1 ranking to residents, along with the many organizations and professionals that promote healthful living.

She said district officials will continue to review the information that produced the rankings, along with other assessments, data and reports on the health of Delaware County residents.

The full county health rankings can be found at www.countyhealthrankings.org.