County-level patterns in mortality rates by cause have not been systematically described but are potentially useful for public health officials, clinicians, and researchers seeking to improve health and reduce geographic disparities.
Dr Laura Dwyer-Lindgren and colleagues demonstrated the use of a novel method for county-level estimation, and estimated annual mortality rates by US county for 21 mutually exclusive causes of death from 1980 through 2014.
Redistribution methods for garbage codes, and small area estimation methods were applied to death registration data from the National Vital Statistics System to estimate annual county-level mortality rates for 21 causes of death.
The team ranked these estimates to ensure consistency between causes and with existing national-level estimates.
Geographic patterns in the age-standardized mortality rates in 2014 and in the change in the age-standardized mortality rates between 1980 and 2014 for the 10 highest-burden causes were determined.
The team's main outcome was cause-specific age-standardized mortality rates.
A total of 80,412,524 deaths were recorded from 1980 through 2014, in the United States.
Of these, about 19 million deaths were assigned garbage codes.
The research team analyzed mortality rates for 3110 counties or groups of counties.
The team observed large between-county disparities for every cause.
The gap in age-standardized mortality rates between counties in the 90th and 10th percentiles varied from 14 deaths per 100,000 population for cirrhosis and chronic liver diseases, to 147 deaths per 100,000 population for cardiovascular diseases.
The researchers noted that geographic regions with elevated mortality rates differed among causes.
Counties also varied widely in terms of the change in cause-specific mortality rates between 1980 and 2014.
For most causes, for example neoplasms, both increases and decreases in county-level mortality rates were observed.
Dr Dwyer-Lindgren's team concludes, "In this analysis of US cause-specific county-level mortality rates from 1980 through 2014, there were large between-county differences for every cause of death, although geographic patterns varied substantially by cause of death."
"The approach to county-level analyses with small area models used in this study has the potential to provide novel insights into US disease-specific mortality time trends, and their differences across geographic regions."