The healthiest place to reside in California is upscale Marin County.
The least healthy is Del Norte County and other sparsely populated, rural areas in the northernmost reaches of the state.
For the first time, researchers released health rankings Wednesday for more than 3,000 counties nationwide.
The rankings enable residents to compare how their county stacks up against others within each state based on how long people live, how healthy they are, the quality of medical care, access to healthy food, air pollution, percentage of residents who smoke or are obese, and numerous other categories.
Several Bay Area counties ranked among the healthiest in California, including Santa Clara County at fourth-best, and San Mateo County at fifth.
Contra Costa County came in at 19th, Alameda County at 23rd, and Solano County at 28th. Researchers analyzed 56 of the 58 California counties.
The study, by the Robert Wood Johnson Foundation and the University of Wisconsin's Population Health Institute, found wide disparities.
Many of the lowest-ranked counties had premature death rates two to three times higher than other counties. The deaths often were caused by preventable conditions.
"These rankings demonstrate that health happens where we live, learn, work and play," said Dr. Risa Lavizzo-Mourey, president and CEO of the Robert Wood Johnson Foundation.
She said that she hopes communities will use the rankings to help mobilize leaders to improve health in their area.
Many factors contribute to the disparities, health leaders say, beyond whether residents adopt healthy behaviors.
"It's easier for people to lead a healthy lifestyle when they live in a healthy community, such as one that has expanded early childhood education, enacted smoke-free laws, increased access to healthier foods, or created more opportunities for physical activity," said Dr. Patrick Remington, associate dean for public health at the University of Wisconsin School of Medicine and Public Health.
The findings mirror on a county level the Bay Area News Group report in December that revealed wide health disparities among East Bay ZIP codes.
The series, titled "Shortened Lives: Where You Live Matters," noted a 16-year difference in life expectancy among those living just a few miles apart. The series also revealed wide differences in rates of asthma hospitalizations, heart disease and cancer death.
Scott Morrow, a San Mateo County health officer, said he was not surprised by his county's high ranking in the study.
"That's reflective of our affluence," he said. "San Mateo County has few pockets of poverty."
Morrow noted that in the United States, the healthiest areas are typically the wealthiest. "It's a reflection of U.S. social policy as much as anything else," he said.
The study found that those living in the healthiest counties tend to have higher education levels, are more likely to be employed, have access to more health care providers, and have better access to healthy foods, parks and recreational facilities.
The least-healthy counties are more likely to have high poverty and unemployment rates, more liquor stores and fast-food outlets, and higher obesity and smoking rates.
Despite San Mateo County's relative affluence, Morrow noted that it has a 15-year difference in life expectancy based on residents' race and where they live in the county.
A Contra Costa County health leader praised the study but said it does not reveal the entire story because it misses the differences that exist within each county.
"There are wide health disparities within Contra Costa," said Dr. Wendel Brunner, the county's public health director.
He noted that children living in San Pablo and Richmond have much higher asthma hospitalization rates than other youths in the county.
The study ranked Contra Costa County as the best in the state for physical environment, including air quality, access to healthy food and lower rates of liquor stores.
But Brunner noted that neighborhoods near busy freeways in Contra Costa still suffer health consequences from diesel emissions.
The rankings "underscore the need for local health departments to continue their important work to delve even deeper to address health disparities and inequities for all people living in a county," Brunner said.
Contact Sandy Kleffman at 925-943-8249.
Find the report on the health of counties throughout the nation at www.countyhealthrankings.org.
Review the Bay Area News Group series on health inequities in the East Bay, including an interactive map where you can check your ZIP code, at ContraCosta
HEALTHIEST CALIFORNIA COUNTIES
Sierra and Alpine counties were not ranked.