Plateauing Cardiovascular Disease Rates in Type 2 Diabetes Concealing Growing Income-Based Disparities, Study Finds

Baiju Shah, MD, PhD

An analysis of data from a 25-year period is raising concern related to the misrepresentation of cardiovascular disease rates among people with type 2 diabetes since the mid-1990s.¹

Although the community has made historic strides in reducing cardiovascular risk in people with type 2 diabetes, results of the study, which included data from more than 1.5 million people recorded from 1995-2019, suggests the apparent stabilization in rates of stroke, heart failure, and amputation is concealing growing income-based disparities, with wealthier patients continuing to see declines in event rates as lower-income patients have seen rates increase.

“During a quarter-century of follow-up, cardiovascular hospitalization rates among people with diabetes fell. However, the apparent stabilization in rates of stroke, heart failure, and amputation in recent years masks the fact that rates have risen for lower-income individuals,” wrote investigators.

The efforts made in reducing incidence of cardiovascular disease globally is widely considered to be among the greatest achievements of public health in history, with so much progress some are arguing cancer may be a greater long-term concern for people with diabetes than cardiovascular disease.² Citing an interest in developing a greater understanding of income-related disparities in cardiovascular events and other adverse events, a team led by Baiju Shah, MD, PhD, and colleagues based in Ontario, Canada sought to provide clinicians with insight into contemporary trends by performing an analysis of data from within population-level health care administrative databases.

With this in mind, investigators designed their study using patient data recorded within administrative databases collecting information from the entire population of Ontario, Canada with a diagnosis of diabetes from 1995-2019. From their search, investigators identified 1,697,504 people with diabetes followed for a median of 9.2 (interquartile range [IQR], 4.5-15.0) years, with a total follow-up of more than 17.5 million person-years. The primary outcome of interest for the study were the rates of acute myocardial infarction, stroke, heart failure, and lower-extremity amputation in annual cohorts, with plans to stratify results according to age, sex, and income level.

Initial analyses revealed the rate of acute myocardial infarction declined through the 25-year study period (P <.0001), with investigators highlighting the rate of acute myocardial infarction observed in 2019 being less than half of the rate observed in 1995 (7.2 vs 15.4 hospitalizations per 1000 person-years). Comparable declines were observed for rates of stroke (3.9 vs 10.8 hospitalizations per 1000 person-years), heart failure (15.9 vs 29.8 hospitalizations per 1000 person-years), and amputation (2.1 vs 4.4 hospitalizations per 1000 person-years) (P for all <.0001).

Stratified analyses revealed the overall rates of stroke, heart failure, and amputation in the 2010s concealed a growing income-related disparity, with rates for higher-income patients decreasing and rates among lower-income patients increasing (P for interaction <.0001 for all 4 outcomes). Investigators highlighted hospitalization rates for heart failure, which decreased from 13.8 to 13.1 per 1000 person-years from 2010 to 2019 among the highest-income patients but rose from 17.3 to 19.4 per 1000 person-years in the lowest-income group during this time frame.

“In conclusion, the cardiovascular hospitalization rates among people with diabetes have fallen over the past 25 years,” investigators wrote. “While acute myocardial infarction rates continue to fall, the declines in the rates of stroke, heart failure, and amputation have stabilized over the past decade. However, this apparent stabilization masks a growing income-related disparity in cardiovascular outcomes among people with diabetes.”

References:

1. 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. 2023. doi:10.2337/dc22-1936
2. Campbell P. 20-year study finds cancer mortality on the rise people with type 2 diabetes. HCP Live. https://www.hcplive.com/view/20-year-study-finds-cancer-mortality-on-the-rise-people-with-type-2-diabetes. Published January 25, 2023. Accessed February 1, 2023.