Income level correlates to a higher risk for stroke, myocardial infarction (MI), heart failure, and amputation among individuals with diabetes, according to study results published in Diabetes Care.
In the study, researchers used records from administrative population-level health care databases in Ontario, Canada, for information from fee-for-service billing claims, the Registered Persons Database for demographic information on Ontario residents, and the Discharge Abstracts Database for detailed information on hospital admissions in Ontario.
Data were classified into annual cohorts, from 1995 to 2019, of all individuals diagnosed with diabetes, as of April 1 each year. Annual cohorts were stratified by age, income level, and sex. Income was determined ecologically based on the average income for each individual’s neighborhood.
Researchers identified hospitalizations related to diagnoses of MI, stroke, heart failure, and nontraumatic lower-extremity amputation, as well as hospitalizations for acute appendicitis, as a negative control outcome.
A total of 1,697,504 individuals with diabetes were evaluated, with a median of 9.2 years of follow-up and more than 17.5 million person-years (PYs) of follow-up.
Researchers found that the rate of MI among individuals with diabetes declined (P <.0001), with the rate in 2019 at less than half the rate in 1995 (7.2 vs 15.4 hospitalizations per 1000 PYs, respectively).
Comparable declines between 1995 and 2019 were seen in the rates of stroke (10.8 to 3.9 hospitalizations per 1000 PYs), heart failure (29.8 to 15.9 hospitalizations per 1000 PYs), and amputation (4.4 to 2.1 hospitalizations per 1000 PYs, with P <.0001 for each outcome). Declines slowed between 2010 and 2019.
Regarding hospitalizations by income level, the researchers found that higher-income patients showed decreasing rates of all cardiovascular outcomes between 2010 and 2019. In comparison, hospitalization rates among lower-income patients increased (P for interaction <.0001 for all cardiovascular outcomes).
Researchers revealed that income-related gradients increased for all cardiovascular outcomes over time. They found, by 2019, the ratio of the hospitalization rate in the lowest-vs highest-income group was 1.29 for acute MI, 1.37 for stroke, 1.49 for heart failure, and 1.78 for amputation.
Researchers conducted additional analyses that showed that men vs women with diabetes were at higher risk for MI and amputation. The relative difference between sexes increased over time (P <.0001). Absolute hospitalization rates for stroke and heart failure were similar between the sexes (P =.005 and P <.0001). Stratification by age showed a predictable age-related gradient in cardiovascular disease risk, with declines in MI and stroke risk for older age groups (P <.0001).
Limitations include the inability to control for changes in clinical care and hospitalization pathways during the study period; the inability to distinguish between the diabetes types; and that income could not be ascertained at an individual level but by proxy measures.
In conclusion, the study team found that health outcomes are improving for Canadians with diabetes.
“However,” the study authors noted, “[T]his apparent stabilization masks a growing income-related disparity in cardiovascular outcomes among people with diabetes.”
Shah BR, Austin PC, Ke C, Lipscombe LL, Weisman A, Booth GL. Growing income-related disparities in cardiovascular hospitalizations among people with diabetes, 1995 to 2019: population-based study. Diabetes Care. Published online January 31, 2023. doi:10.2337/dc22-1936