AIM: Early & late diabetes onset associated with increased CVD risk
Both an early and late onset of diabetes was associated with an increased risk of major cardiovascular disease (CVD) events and mortality in men between the ages of 60 to 70; however, early onset with a mean duration of 10 years was equal to the risk of a previous MI, according to research published in the March 14 issue of the Archives of Internal Medicine.

“The increased CVD risk associated with diabetes is not fully explained by traditional CVD risk factors,” the authors wrote. “Although diabetes is a well-established risk factor for CHD [coronary heart disease], whether diabetes alone is a CHD equivalent in assessing the risk of future CVD events is controversial.” Some studies have suggested that diagnosis of the condition after the age of 65 is not associated with increased mortality.

To better understand the influence of age on the impact of diabetes on CVD risk, S. Goya Wannamethee, PhD, of the University College London, and colleagues used data from the British Regional Heart Study of CVD to evaluate 4,045 men between the ages of 60 to 79 years old.

During the mean nine-year follow-up, the authors reported 372 major CHD events (263 CHD deaths) and 1,112 deaths from all causes—455 were attributed to CV causes. The average onset of diabetes was 16.7 years compared with 1.9 years in men with late onset of the comorbidity.

The patients with an early-onset of diabetes showed higher levels of homeostasis model assessment (HOMA), blood glucose and hemoglobin compared with those with late-onset diabetes. The authors reported that men with diabetes or MI showed a significantly greater risk of major CHD compared with those with neither MI nor diabetes, but men with an early onset of diabetes showed a similar risk to men who had a history of MI.

Most men diagnosed with an early onset of diabetes were diagnosed at 30 years or older, but both late and early onset of diabetes was associated with a significantly higher risk of CVD events. Patients with an early onset of the condition had a higher risk of major CVD events of occurring and had an intermediate risk compared with early and late development of MI, the authors noted.

Likewise, the patients with diabetes and a previous MI had higher total mortality compared with patients with no diabetes and no MI; however, patients with an early onset of diabetes had the highest risk of mortality.

Wannamethee et al also reported that those with diabetes for eight years or more had an increased risk of CVD and mortality compared with patients who had a duration that was less than two years.

“Our present analysis shows clearly the importance of the timing of development of diabetes (linked to the duration of diabetes) on such risk,” the authors wrote.

Overall, patients with a later onset of diabetes (those diagnosed at the age of 60 or over) had a CHD risk that was almost half of that in persons who were diagnosed with diabetes prior to the age of 60 and had a mean duration of 16.7 years. Additionally, the relative risk for vascular events and mortality in patients who had an early onset of diabetes were comparable to men with a prior MI, “suggesting that a longer duration of diabetes may be necessary to raise risks toward a CHD risk equivalent,” the authors noted.

Findings of the study add to previous research that showed that CHD risk in diabetes intensifies when disease duration goes beyond eight years. The authors speculated that patients who develop diabetes later in life may be phenotypically different—less insulin resistant and retaining greater beta-cell dysfunction. The authors also said that longer exposure to chronic hyperglycemia could be part of the explanation as to why diabetes duration was associated with a risk of CHD.

“In the light of current trends of rising prevalence of type 2 diabetes combined with a decline in the average age at onset, these findings emphasize the critical importance of age at development of diabetes and thus of diabetes duration on cardiovascular risk and the seriousness of the CVD consequences of the emerging type 2 diabetes epidemic,” the authors concluded.

In an accompanying Archives editorial, Islandar Idris, DM, of the End University of Sheffield wrote, "Correctly identifying and treating individuals who are most at risk of CHD will confer the most cost-effective public health strategy for primary prevention of CHD.

"To this end, the need to reconcile any discordance between the impact of age threshold and disease duration on CHD risk stratification in patients with diabetes is important. An obvious approach is to use both strategies," he concluded.