Study reveals widening urban-rural gap in diabetes-related mortality in US

A new study published in Diabetologia has found a widening gap in diabetes-related mortality between urban and rural areas in the USA.

The researchers, led by Dr Mamas A Mamas of Keele University, also found that reductions in mortality rates seen predominantly in urban areas have been mainly limited to female and older patients while outcomes in male and younger individuals worsened.

The authors analysed 20 years of data from the CDC’s Wide-Ranging online Data for Epidemiologic Research (CDC WONDER) Multiple Cause of Death database which recorded the cause of death of every US resident who died in the period 1999-2019.

Each death certificate recorded a single underlying cause with up to 20 additional factors, as well as demographic data such as age, sex and ethnicity, and deaths were grouped by county to calculate age-adjusted mortality rates (AAMRs) per 100,000 population for urban and rural areas.

Between 1999 and 2019 there were 1,572,536 deaths (80% in urban counties) where diabetes was given as the underlying cause and 5,025,745 deaths (again 80% in urban counties) with diabetes as a contributory factor.

The team found that the AAMR of diabetes patients was higher in rural areas across all age, sex, and ethnicity groups and over the 20-year period of the study there was no statistically significant change in the AAMR of diabetes as the underlying or contributing cause of death in rural areas.

By contrast, urban areas saw a significant decrease in the AAMR of diabetes as the underlying (−17%) and contributing (−14%) cause of death over the same time period. As a result, the urban-rural diabetes-related mortality gap has tripled in the USA, rising from 2.0 to 6.8 deaths per 100,000 population for diabetes as the underlying cause, and from 6.8 to 24.3 deaths per 100,000 population for the disease as a contributing factor, with the main impact being felt by male patients and those under-55 years old.

In both urban and rural areas, AAMRs were higher in males and saw a significantly smaller decrease than in females leading to a widening of the male-female diabetes mortality gap. Among under-55s there was an increase in diabetes-associated AAMRs over the time period which was larger in rural (+59% underlying, +65% contributing) than urban (+15% underlying, +14% contributing) populations. This contrasted with the over-55s who experienced a decrease in AAMRs in urban (-21% underlying, -16% contributing) residents and no statistically significant change (-5% underlying, +4% contributing) in rural areas.

Ethnicity was also linked to mortality with American Indian and Black individuals having substantially higher diabetes-related AAMRs than Asian and White patients, and within each ethnic group, rural living was associated with higher mortality. For example, in rural areas, the mortality amongst Black patients remained similar between 1999 and 2019, whereas it decreased by 28% in urban areas. Diabetes-related AAMRs in 2019 were twice as high in Black patients compared to White patients, in both rural and urban settings.

The authors highlighted that successful management of diabetes and the control or prevention of associated complications requires medical expertise that may be unavailable or difficult for rural populations to access. Patients in these communities are also less likely to have their primary care delivered by physicians, and they have been further impacted by the disproportionate closure of rural hospitals.

The urban-rural divide is inextricably linked to social determinants of health including education, economic resources, psychological stress and access to preventive healthcare.

Photo by David Moruzzi