The varying degrees of life expectancy across geographic regions in the United States is something scientists have been studying for years, but until now little research had been done on the specific causes of death contributing to these mortality rates.
A new study, published in the Journal of the American Medical Association looked at trends in mortality across the U.S. between 1980-2014 and researchers from the Institute for Health Metrics and Evaluation at the University of Washington determined the most common causes of death for 3,110 different U.S. counties. You can see a visualization of the data in an interactive map on their website.
"We know that the risk someone will die varies quite a bit from place to place, and it's reasonable to guess that the things people die of also vary from place to place," Laura Dwyer-Lindgren, lead study author and researcher at the Institute for Health Metrics and Evaluation, told Seeker.
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"Until now, our knowledge of how mortality from specific causes varies by county was patchy at best," she added. "The goal of our analysis was to produce the best estimates possible of mortality rates by county for 21 major causes of death and to enable meaningful comparisons across causes, across counties, and over time."
Between Jan. 1, 1980, through Dec. 31, 2014, 80.4 million deaths were recorded in the U.S. For this 34 year period, researchers looked at death records from the National Center for Health Statistics, which included information on age, sex, county of residence and the official cause of death for each deceased person in the data set.
The data analysis focused primarily on the 21 most common causes of death, some of which include diseases like HIV/AIDS, cancer, cardiovascular diseases, and neurological disorders, as well as substance abuse and mental health, transport injuries, self-harm and forces of nature.
Because this study centered around relatively small geographic areas, some results surprised the researchers, who had never seen cause of death information at such a local level before.
"Mortality from mental and substance use disorders showed dramatic variation between counties, from three deaths per 100,000 people in Sioux County, Iowa, to 73 deaths per 100,000 people in Rio Arriba County, New Mexico," said Dwyer-Lindgren.
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Although the data represents county-level information, regional trends were also observable. For example, across the southern part of the Mississippi River, cardiovascular disease was typically the highest cause of death, while in the southwest, self-harm and interpersonal violence were most common.
The occurrence and increase of mental health and substance abuse deaths in certain counties was also somewhat surprising to researchers. "Between 1980 and 2014, the mortality rate due to mental health and substance use disorders increased in nearly every county, with clusters of counties in Kentucky, West Virginia, and Ohio revealing increases upwards of 1,000 percent," Dwyer-Lindgren commented.
In addition to cardiovascular disease, neurological disorders were a common cause of death in the south as well.
"76 percent of counties experienced an increase in deaths from neurological disorders, including Alzheimer's disease, epilepsy and other disorders, with the largest increases in southern counties stretching from eastern Texas and Oklahoma to Alabama," Dwyer-Lindgren added.
Interestingly, the results also showed that the county with the highest rate of mortality and the lowest rate of mortality for cirrhosis and other liver diseases were both located in South Dakota.
Dwyer-Lindgren explained that while the study didn't focus on precisely identifying the reasons for health disparities in our country, certain factors that may contribute to the differences in cause of death were evident.
"Differences in risk factors such as smoking and obesity, differences in socio-economic factors such as income and education, and differences in access to care and quality of care may explain part of the differences we see in mortality rates," she said. "Further research must be done to provide evidence on the particular drivers of causes of deaths."
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Information like this has the power to provide insights into disease-specific mortality trends over time, and how they differ based on geographic regions. But can people reasonably predict how they're going to die based on which part of the country they live in? Unsurprisingly, the answer is complex.
"There are certainly some environmental and location factors that are important. Living in an area of high radon levels will increase the likelihood of dying of lung cancer, and living in the northern part of the US will increase the likelihood of dying of prostate cancer," Dr. Peter Rogerson, distinguished professor of geography at SUNY Buffalo, told Seeker.
"It is also important to recognize that counties themselves are heterogeneous," he added. "They are complex averages of varied people and places. The varied subregions within counties can have... very different health outlooks and life expectancies, and because of this, the reliability of such prediction is seriously limited."
While this data might not be able to predict how you'll die, Dwyer-Lindgren believes it could be used to help lower the mortality rate in the United States by improving public health at the local level.
"State and county health departments could use county-level data to identify pressing local needs and tailor their policies appropriately," she suggested. "Physicians could use the estimates to better understand the health concerns of the populations they serve, and people can use these estimates to understand the health needs of their community and advocate for change."
Ultimately, Dwyer-Lindgren and her team are hopeful these findings will be used to improve the health of Americans throughout the country.
"We hope that these county-level mortality findings will be used to push for targeted health programs that address the unique needs of communities across the nation," she said.
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