Adults with type 2 diabetes that don't take their medicine consistently has a 27 percent higher rate of heart disease according to new study. The effect hit younger patients even harder.
Type 2 diabetes is associated with an increased risk of heart disease. So many people with type 2 diabetes are prescribed blood sugar-lowering medication to reduce this risk.
Diabetes medications help keep blood sugar levels under control. High blood sugar over many years can damage blood vessels and the heart, increasing the risk of heart attacks and other cardiovascular diseases. By adhering to these medications and maintaining low blood sugar, this damage is reduced and help protect the heart.
Source: Associate Professor Jordi Merino
However, not everyone takes their medication consistently, and that inconsistency could leave them more exposed. Yet scientists have struggled to pin down how much long-term adherence, meaning how reliably someone sticks to a prescription over the years, actually changes a person's risk of a heart attack or stroke.
Now, researchers at the University of Copenhagen and their collaborators have tracked the medication habits of nearly 80,000 adults over ten years to find out. They found that people who consistently took their prescribed diabetes treatment stayed free of serious heart and circulatory complications for more than seven extra months compared with those who did not.
"Prescribing the right medicine is only the first step. Our study shows, that whether a person is actually able to keep taking their treatment in the following years, has a real bearing on their heart health. That makes a strong case for offering people personalised support early, soon after they are diagnosed, rather than assuming a prescription on its own is enough," says Associate Professor Jordi Merino from the Novo Nordisk Foundation Center for Basic Metabolic Research (CBMR) at the University of Copenhagen, who led the study.
Mapping a decade of prescriptions
To see how real-world habits unfold, the team turned to Denmark's national health registries. They analysed records from 79,510 adults who were newly diagnosed with type 2 diabetes and started taking non-insulin medication between 2005 and 2012.
Rather than relying on self-reported answers, the researchers used a statistical method that followed monthly pharmacy records across a ten-year period.
This grouped patients into three clear patterns. Around 41 percent kept up high adherence, 33 percent settled into moderate adherence, and 26 percent dropped off early and stayed at persistently low adherence.
People in the low adherence group had a 27 percent higher rate of major cardiovascular events compared to people who took their medication consistently. Even the intermediate group faced a seven percent higher rate.
The link was strongest for ischemic heart disease, where low adherence was tied to a 45 percent higher rate. People with low adherence also had a 24 percent higher rate of stroke.
The risk weighs heaviest on younger patients
The stakes were higher still for younger adults. Among younger adults, low adherence was linked to a 73 percent higher rate of having a cardiovascular event before the age of 55, compared with consistent users. Developing type 2 diabetes early in life carries a heavier lifetime risk of damage to the blood vessels, so keeping up treatment from the start matters most during the peak working and family years.
The study also pointed to a social dimension. People in the low adherence group were more likely to live alone, to have lower incomes, and to manage other chronic conditions. Skipping medication, in other words, is rarely just forgetfulness. It often reflects wider pressures in a person's life.
Tracking habits over the long term could help doctors spot vulnerable patients before a major heart event happens.
To account for this, the researchers adjusted their analyses for these and other important factors. After taking them into consideration, they still found that people who were less adherent to their diabetes medications had a higher risk of developing cardiovascular disease.
"These findings show that health systems need to move beyond checking medication habits once or twice a year. Having access to medicine does not automatically mean a person can take it every day, so tracking habits over the long term could help doctors spot vulnerable patients before a major heart event happens," says first author Researcher Lise B. Nielsen from CBMR.
About the research
- Because the study is an observational study, the researchers cannot prove that poor medication adherence directly causes heart disease. However, the findings are consistent with extensive evidence showing that maintaining good blood sugar control through appropriate treatment helps reduce the risk of cardiovascular complications.
- People who do not take their prescribed medications are often more likely to have other challenges, such as lower incomes, living alone, or additional health conditions, which can also affect their heart health. Additionally, the study does not measure potential outside factors like blood sugar regulation, body mass index or lifestyle behaviour.
- The researchers account for this by adjusting for socioeconomic indicators and through a number of sensitivity analyses. They still found that people who were less adherent to their diabetes medications had a higher risk of developing cardiovascular disease.
- Prescription redemption was used as a proxy for medication intake, however this is a standard practice for registry-based studies.
- The study and the researchers were partly supported by grants from the Novo Nordisk Foundation. This had no impact on the design and publication of the study.
- The study is published in the scientific journal The Lancet Regional Health - Europe.
- Researchers from the University of Copenhagen who contributed to the study include: Lise B. Nielsen, Andreas Bartholdy, Tri-Long Nguyen, Majken K. Jensen, Simon Rasmussen, Marta Guasch-Ferré and Jordi Merino.
