Persistent Disparities in Diabetes Mortality Observed in US Rural Counties

Sagar B. Dugani, MD, PhD, MPH

New cross-sectional findings suggest rural counties in the United States had the highest overall diabetes mortality rate in comparison with other urbanization levels.

Subnational disparities, including a higher annual diabetes mortality rate (ADMR) in men in rural counties, those aged 25 to 54-years in all urbanization levels, and the rural Southern region, were observed by study investigators.

“Taken together, the results describe subnational trends in diabetes mortality, highlight persistent rural disparities, and identify areas for investigation and intervention.,” wrote study author Sagar B. Dugani, MD, PhD, MPH, Division of Hospital Internal Medicine, Division of Health Care Delivery Research, Kern Center for the Science of Health Care Delivery, Mayo Clinic.

The prevalence of diabetes and access to care can be impacted by factors including rurality and trends in mortality. Still, rural populations often have sparse information available on these trends, limiting the development of interventions to reduce death.

From 1990 to 2007, the age-standardized incidence rate of diabetes increased and then decreased through 2017. But, longitudinal trends on diabetes-related mortality are incompletely described and national trends may not reflect subnational trends.

In order to examine diabetes rates and trends, the US Centers for Disease Control and Prevention Wide-Ranging Online Data for Epidemiologic Research (CDC WONDER) database was examined from January 1999 to December 2018.

Study investigators grouped mortality by region (Midwest, Northeast, South, or West), county urbanization (meto, medium-small, or rural), age group (25 - 54, 53 - 74, or ≥75 years), and gender (men or women) in 2-year groups.

They used weighted multiple linear regression models and jackknife resampling with a 3-segment time component. Models included exposures with up to 3-way interactions and were age-standardized to the 2009 - 2010 population. ADMR was calculated per 100,000 people.

The analysis was based on 4,022,238,309 person-years in adults 25 years or older, with diabetes being a multiple cause of death for 4,735,849 adults (annual mean, 117.7 deaths oer 100,000 people).

Increasing rurality was linked to a lower proportion of women and a higher proportion of adults 55 years or older. The overall population saw the ADMR was highest in rural areas compared with medium-small and metro counties.

Data suggest the ADMR in 2017-2018 vs 1999-2000 were highest and unchanged in rural counties (157.2 [95% CI, 150.7 - 163.7] vs 154.1 [95% CI, 148.2 - 160.1]; P = .49).

It was significantly lower in medium small counties (123.6 [95% CI, 119.6 - 127.6] vs 133.6 [95% CI, 128.4 - 138.8]; P = .003) and urban counties (92.9 [95% CI, 90.5 - 95.3] vs 109.7 [95% CI, 105.2 - 114.1]; P <.001).

Mortality rates were higher in men in rural counties in 2017 - 2018 compared with 1999-2000 (+18.2’ 95% CI, 14.3 - 22.1), but were unchanged in medium-small counties and significantly lower in metro counties.

Meanwhile, in 2017 - 2018 vs 1999-2000, the ADMR was significantly lower for women at all urbanization levels, but the smallest magnitude of decrease was seen in rural counties (-14.0; 95% CI, -17.7 to -10.3; P <.001).

Age was additionally a factor, as the ADMR was significantly higher in older age groups within all urbanization levels. The 25- to 54-year age group had the largest magnitude of increase in rural counties (+9.4’ 95% CI, 8.6 - 10.2) when compared with medium-small and metro counties.

Region-specific diabetes mortality by urbanization suggested the mortality rate in 2017-2018 versus 1999-2000 was higher only in the rural South (+13.8; 95% CI, 7.6 - 20.0; P <.001).

“Regional differences in the ADMR may be linked to differences in disease burden, with a higher age-adjusted prevalence of diabetes in the South, modifiable risk factors (eg, physical activity),environmental pollution, and race or ethnicity, among other factors,” Dugani added.

The study, “Assessment of Disparities in Diabetes Mortality in Adults in US Rural vs Nonrural Counties, 1999 - 2018,” was published in JAMA Network Open.