Women are six times more likely to die from breast cancer in different counties within the same state due to a zip code lottery, a first-of-its-kind study shows.
The variations from county to county reflect the different degrees of influence that major risk factors have for dying of breast cancer, including obesity and a history of smoking.
Researchers in Virginia used federal data to look at breast cancer deaths in more than 2,000 counties to map out differences in mortality rates.
Death rates can vary drastically from one county to its neighbor, such as Lamar County, Alabama, where approximately one in 33 women overall die of breast cancer compared to nearby Cullman where that rate is as high as one in nine.
The researchers said: ‘These results suggest that breast cancer mortality in the US can be affected by where individuals live, and that more comprehensive and geographically targeted interventions may lead to healthier communities.’
Counties are colored in shades of purple. The researchers’ work showed not only which states have higher breast cancer death rates, but also those rates in individual counties. Alabama, for instance, is an example of significant county-by-county variation. The northern part of the state showed more variation in mortality rates than the southern region
Breast cancer is the leading cause of cancer-related deaths among women in the US, but death rates have plummeted 43 percent between 1989 and 2020
The authors added: ‘Alabama is a clear example of the diverse outcomes experienced by breast cancer patients based on their geographic location even under unified state programs.
‘While the northern part of the state showed significant variation in age-adjusted mortality rates between counties, the southern part of the state displayed more homogeneous rates.’
Alabama was not the only state showing a collection of counties with vastly different death rates. For instance, the mortality rate hovered between nine and 17 per 100,000 women in Person County, North Carolina. But in Caswell County right next door, that rate fell within the range of 25 to 33 per 100,000 women.
In Garfield County, Utah, between one in 33 and one in 57 die of breast cancer, compared to one in nine to 17 in neighboring Iron County.
In Putnam County, Ohio, between one in 25 and one in 33 die of breast cancer compared to Paulding County right next door, where an estimate one in 17 to 21 die of the same cause.
And in Okanogan county, the mortality rate ralls between 33 and 57 deaths per 100,000 people, compared to nine to 17 per 100,00 in Douglas County directly south.
Different variables that contribute to fatal breast cancer cases had difference levels of impact.
Obesity was influential in 100 percent of the counties, but those in the southeastern US had marginally higher coefficient rates, meaning obesity rates had a slightly higher impact in those counties
Counties in red have lower coefficient ranges than yellow-shaded counties, meaning that while access to the preventative breast x-rays was universally influential, the relationship between access to mammograms and breast cancer deaths was strongest in eastern states
In the south and east, whose counties are colored in shades of yellow and orange, the association between access to nutritious food and breast cancer death rates is represented by a coefficient range of −1.55 to −2.85, while the west’s coefficient fell between -1.07 to -0.36. However, the map shows pockets in Ohio, Pennsylvania, Tennessee, and Kentucky where the relationship between the two is stronger than the region overall
They found that obesity rates in certain areas, particularly a long string of counties in Bible Belt states, had a stronger link to breast cancer deaths than those in the Pacific Northwest. In eastern states, mammogram access influenced mortality.
Obesity contributed to deaths in every county the researchers looked at, but smoking cigarettes was estimated to have a hand in driving up death rates in fewer than 17 percent of counties.
And whether people in a county had access to nutritious, healthy food influenced death rates in over 80 percent of counties.
Access to healthcare services, including preventative measures such as mammograms, had a universal impact on deaths due to breast cancer. As more women underwent X-rays to detect cancer, fewer died.
And while breast cancer is the most common type among women, with more than 264,000 diagnosed every year in the US, mammograms and other screening tools as well as innovations in cancer treatments have helped tamp down death rates.
Deaths due to breast cancer have plummeted 43 percent between 1989 and 2020 after successful public health awareness campaigns, better screening, and new drugs.
To help researchers dive deep into county-level data, the researchers relied on two methods of statistical analysis – Ordinary Least Squares (OLS) and Multiscale Geographically Weighted Regression (MGWR).
The relationship between breast cancer deaths and different variables that influence those, including access to healthy food and mammograms, is shown using a coefficient, or a number that shows the strength of a relationship between two variables.
A higher coefficient number indicates a stronger relationship.
Both models showed that the effects of mammogram uptake and obesity had a uniform impact, which allowed the researchers to see that those relationships were strongest in most counties spanning North Carolina and Florida to eastern Oklahoma and Texas.
They also determined that mammogram access had an even stronger influence on keeping breast cancer death rates low in most counties on the eastern seaboard stretching from Maine to North Carolina.
The food environment was influential in most counties but even greater in southern and eastern states’ counties compared to the western US.
Obesity had an even stronger impact on southern states’ counties compared to the west.
The findings were published in the journal JAMA Network Open.