(CNN) -- Deaths due to heart problems tend to be highest in counties along the southern half of the Mississippi River.
Violent deaths tend to be common in Western counties, and deaths from mental and substance abuse disorders tend to be more common in Kentucky and West Virginia counties than others.
Those are just a few of the trends that emerged in a new study that revealed the major causes of death for counties across the United States. The study was published in the journal JAMA on Tuesday.
"We know that unequal access and quality of care create health disparities in the US for many causes of death, while other causes are linked to risk factors or policies. The results of this study prompt future research to further identify what drives health disparities in our country," said Dr. Christopher Murray, a professor and director of the Institute for Health Metrics and Evaluation at the University of Washington, who was a co-author of the new study.
For the study, researchers analyzed death records from the National Center for Health Statistics' National Vital Statistics System. The records included data on 80,412,524 deaths that occurred from 1980 through 2014 in the United States.
The data included the county of residence for each person who died, at the time of their death, but did not include data on deaths of Americans outside the United States.
After taking a close look at which causes of deaths occurred in which counties, the researchers found trends in how many deaths were due to tumors; cardiovascular disease; diabetes and diseases that affect the urinary tract, genitals, blood, thyroid or pancreas; neurological disorders; suicide and violence; chronic respiratory diseases; transportation-related injuries; mental and substance disorders; chronic liver diseases; and infectious diseases.
The 2014 mortality rates and geographic patterns in the data are a good indicator of current trends, Murray said.
The findings appear to be the most comprehensive yet to describe how a broad set of causes of death differ across counties, said Ellen Meara, a professor at the Dartmouth Institute for Health Policy and Clinical Practice in New Hampshire, who was not involved in the new study.
"It is unique in its ability to track cause-specific death rates in small areas over a long time period, three decades," Meara said of the study.
The study showed very high mortality rates due to tumors, especially when cancerous, in counties along the southern half of the Mississippi River, eastern Kentucky, western West Virginia and western Alaska.
However, many counties in states stretching from Idaho and Wyoming in the north to western Texas in the south had lower-than-average mortality rates from tumors, according to the results.
Cancer death rates between 2009 and 2013 were highest in Union County, Florida; Wade Hampton Census Area, Alaska; Woodson County, Kansas; Powell County, Kentucky; and other nearby counties, according to separate statistics from the National Cancer Institute's state cancer profiles.
For cardiovascular disease, mortality rates decreased by about 50% overall between 1980 and 2014, but the rate of decline varied by county, according to the study. Slow rates of improvement were observed in Southern counties stretching from Oklahoma to Alabama and Kentucky.
Cardiovascular disease death rates were highest among Franklin, Louisiana; Caldwell, Louisiana; Gallatin, Kentucky; and other nearby counties from 2012 to 2014, according to separate data from the Centers for Disease Control and Prevention's Interactive Atlas of Heart Disease and Stroke Tables.
Heart disease has consistently been the leading cause of death in the United States in recent years, with cancer as a close second, according to data released by the National Vital Statistics System in August (PDF).
The new study also showed that mortality rates due to diabetes and diseases that affect the urinary tract, genitals, blood, thyroid or pancreas were particularly high in counties in Arkansas, Louisiana and Mississippi along the Mississippi River and in counties with Native American reservations in North Dakota and South Dakota.
Large increases in deaths due to neurological disorders were observed in Southern counties stretching from eastern Texas and Oklahoma to Alabama, according to the study. Declines in mortality were found in counties in the West, an area reaching from central Idaho and western Montana to central Colorado.
Increased mortality rates due to chronic respiratory diseases were observed in a prominent cluster of counties in eastern Kentucky and West Virginia and in a second cluster in southeastern Colorado, according to the new study.
The lowest mortality rates were found in counties in the District of Columbia area, the upper Midwest, southern Florida, southern Texas and central Colorado.
Chronic respiratory diseases are often linked to smoking. Other risk factors include air pollution, exposure to chemicals and dusts, and frequent lower respiratory infections in childhood.
For deaths due to mental and substance use disorders, the mortality rate increased by 188% overall between 1980 and 2014, according to the new study.
Several clusters of counties in Kentucky, West Virginia, Ohio, Indiana, western Pennsylvania and east-central Missouri saw mortality rates rise by more than 1,000%.
According to a separate Morbidity and Mortality Weekly Report released by the CDC in January, West Virginia topped the list of states with the highest rates of drug overdose deaths in the country in 2014, followed by New Mexico, New Hampshire, Kentucky and Ohio.
The new study showed that counties in eastern Arizona, New Mexico and south and western Texas were among those with the highest mortality rates for cirrhosis and other chronic liver diseases, whereas counties in eastern South Dakota, Kansas, Iowa and southern Minnesota had the lowest mortality rates. Alcohol abuse has been linked to such liver diseases.
For diarrhea, lower respiratory and other common infectious diseases, mortality rates were highest in counties in Southern states, from Louisiana and Arkansas to Georgia, Tennessee and Kentucky, according to the new study.
Meanwhile, rates were lower than average in counties in southern Florida, New England, the upper Midwest, central Colorado and the Pacific Northwest.
The highest mortality rates due to self-harm and interpersonal violence were observed in counties in Alaska, in Native American reservations in North Dakota and South Dakota, and in states in the Southwest, according to the new study.
Lower rates were found in counties in the upper Midwest, New England, southwestern Texas and southern California.
Additionally, "about half of US counties saw increases in suicide and violence, while the other half of counties experienced decreases," Murray said. "Kusilvak Census Area in Alaska topped the list with a 131% mortality rate increase, while the rate in New York County, New York (which encompasses Manhattan), dropped by 72% -- the most dramatic decrease in the country."
In 2012, Wyoming was the state with the highest suicide rate, followed by Alaska, Montana, New Mexico and Utah, according to a 2014 Morbidity and Mortality Weekly Report.
For deaths due to transportation-related injuries, in general, lower mortality rates were found in more urban counties, and higher mortality rates were found in more rural counties.
Todd County, South Dakota, had the highest mortality rate from transportation-related injuries in 2014, and the county with the lowest mortality rate was New York County, Murray said.
"An interesting finding when deaths are mapped by small areas is the way some causes of death follow state boundaries, which suggests that state policies likely play a role in saving lives," said Meara, the Dartmouth Institute professor.
"Deaths due to transport injuries, for example, look very different north of the Ohio River, in Ohio, Indiana and Michigan, compared with Kentucky," she said. "You can see some of these state-by-state patterns in the maps of deaths due to self-harm and interpersonal violence, as well."
The 2016 County Health Rankings, a separate report conducted by the Robert Wood Johnson Foundation and the University of Wisconsin Population Health Institute in March, also showed dramatic differences in health and deaths between rural and urban communities.
It revealed that rural counties tended to have higher rates of smoking, obesity, child poverty and teen births, as well as higher numbers of uninsured adults, than their urban counterparts.
Additionally, similar to the new study, the County Health Rankings report showed that the average rate of drug overdose deaths appeared higher in rural counties.
Meara said that such county-specific research remains important.
"This research demonstrates that the tools needed to improve health and survival in places like eastern Kentucky, where mortality from chronic respiratory disease is high and rising, differ from the tools needed to address mortality in New Mexico and western Texas, where deaths due to cirrhosis and other chronic liver disease are high and rising," Meara said.
"The typical studies of all-cause mortality mask these differences, leading to one-size-fits all policies that may not be effective. With studies like these, everyone, from clinicians to local and state policy-makers, can better address the needs of their communities," she said.
Although the new study does not offer a definitive conclusion for some big questions, Meara said, "it opens up a new set of important questions about why areas experienced such different trends in particular causes of death. It provides an opportunity to learn from success and failure in different counties."
Overall, life expectancy in the United States has dropped by 0.1 year from last year, according to data released this month from the CDC. Americans can now expect to live 78.8 years.
Murray said he hopes to further examine trends and details in causes of death across the country to help improve public health in communities nationwide.
"State and county health departments could use county-level data to identify pressing local needs and tailor their policies appropriately. Physicians could use the estimates to better understand the health concerns of the populations they serve," Murray said.
"Researchers could identify counties that have done especially well or poor with regard to certain causes of death, warranting additional study to identify factors driving trends. Communities can use these estimates to understand the health needs of their community and advocate for change," he said. "These results could also provide a mechanism for evaluating the effect of certain policies and programs."