Cardiovascular Disease a Continuing Challenge in Type 1 Diabetes

Miriam E. Tucker

August 23, 2021

Despite a significant decline in cardiovascular disease risk for people with type 1 diabetes over time, the risk remains higher than that of the general population, new data from Finland show.

Findings from the study of nearly 12,000 Finnish people diagnosed with type 1 diabetes in childhood, beginning in 1965, by Valma Harjutsalo, PhD, of the University of Helsinki, Finland, and colleagues, have been published in The Lancet Diabetes & Endocrinology.

The data show "a considerable decrease in cardiovascular disease morbidity and mortality in childhood-onset type 1 diabetes over the last five decades in Finland...However, cardiovascular disease morbidity is still several times higher in patients with type 1 diabetes than in the general population," Harjutsalo and colleagues write.

Interestingly, the data show that the reduction in cardiovascular disease among people with type 1 diabetes over the past decades has been steeper than in the general population, yet still remains several times higher.

The findings also point to a major knowledge gap, despite the fact that cardiovascular disease is the main driver of premature mortality in people with type 1 diabetes, especially those with diabetic nephropathy.

"Our results highlight a need for studies on the natural history of atherosclerosis in children and young adults from the diagnosis of diabetes and additional studies on effective early prevention of cardiovascular disease," the authors write.  

The findings generally align with those published in 2018 from a Swedish registry showing a greater decline in cardiovascular disease over time among those with type 1 diabetes than the general population. However, those data were limited to 1998-2014 and didn't account for year of diabetes diagnosis, Harjutsalo and colleagues point out.   

Gap Remains, Much Work Needs to Be Done

In an accompanying editorial, Trevor J. Orchard, MBBCh, of the University of Pittsburgh, Pennsylvania, says the findings "suggest a partial closing of the gap in cardiovascular disease risk between those with and without type 1 diabetes," however, "the gap remains significant and much work still needs to be done."

"More type 1 diabetes research is needed, particularly with regards to the evaluation of vigorous blood pressure and lipid control (including assessment of newly recognized lipid predictors like high-density lipoprotein function), insulin resistance-based interventions, and new drugs like SGLT2 inhibitors," he writes.

"Cardiovascular disease prevention strategies for those with type 1 diabetes should no longer have to be either inferred from the very different type 2 diabetes population or, worse still, left unspecified because of insufficient type 1 diabetes evidence."

Continuous Decline in CVD Risk Over Time

The study population included 11,766 individuals from the database of the Helsinki-based National Institute for Health and Welfare, diagnosed with type 1 diabetes when they were younger than 15 years old between 1965 and 1999. They were followed for cardiovascular disease through the end of 2016 and for mortality until 2017.

Over a median follow-up of 29.6 years, 1761 (15.0%) had a first-ever cardiovascular disease event.

Of a cumulative total of 2686 events, 32% (864) were coronary artery disease events, including 663 acute myocardial infarctions and 497 strokes. Another 32% (854) were peripheral artery disease events, including 498 lower extremity amputations. Heart failure events occurred in 17.5% (497).

Of 2686 with diabetic nephropathy, 40% had cardiovascular events.  

Two thirds (63.9%) with cardiovascular disease had just a single type of event, but 22.6% had two and 11.1% had three.

Over the 50 years, the cumulative incidence of any cardiovascular disease was 45.8% in those diagnosed in 1965-1969. The incidence was significantly higher for men than women (47.6% vs 43.8%; hazard ratio, 1.23; P < .0001).

After adjustment for sex and age at diabetes diagnosis, cardiovascular disease risk decreased by 3.8% over the study period (P < .0001).

However, the authors note, "It is of concern that the decrease in cardiovascular disease morbidity in the individuals in the 1990-94 and 1995-99 cohorts compared with those in the 1980-84 cohort has been only modest."

The cardiovascular disease death rate decreased constantly by diagnosis year.

Faster CVD Decline Than General Population, but Rate Still Higher

Data for the general Finnish population came from the Cardiovascular Disease Register of the National Institute of Health and Welfare.

The excess risks of coronary artery disease and stroke compared with the general Finnish population were estimated using standard incidence ratios (SIRs) for 1991-2014.

There was a decrease in SIRs for both coronary artery disease and stroke within all 10-year age groups under 65 years, except for stroke in the oldest age group.

However, the SIR was 8.9 for coronary artery disease and 2.9 for stroke in those diagnosed with type 1 diabetes in the 1990s.

Harjutsalo has reported no relevant financial relationships. Disclosures for the other authors are listed in the article. Orchard has reported receiving grant review honorarium from Novo Nordisk.

Lancet Diabetes Endocrinol. 2021;9:575-85, 548-9. Study, Editorial

Miriam E. Tucker is a freelance journalist based in the Washington, DC, area. She is a regular contributor to Medscape, with other work appearing in The Washington Post, NPR's Shots blog, and Diabetes Forecast magazine. She is on Twitter: @MiriamETucker.

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