according to the results of a new study.
These findings confirm previous reports and practice guidelines that identify South Asian ancestry as a risk enhancer for atherosclerotic cardiovascular disease (ASCVD), suggesting that earlier heart disease screening and prevention is warranted in this patient population, lead author Aniruddh P. Patel, MD, research fellow at the Center for Genomic Medicine, Massachusetts General Hospital, Boston, and colleagues said.
“Previous studies in multiple countries have estimated a 1.7- to 4-fold higher risk of ASCVD among South Asian individuals, compared with other ancestries, but have important potential limitations,” Dr. Patel and colleagues wrote in the paper on their prospective cohort study, published in Circulation.
The INTERHEART case-control study, for example, which assessed risk factors for acute myocardial infarction among more than 15,000 cases from 52 countries, is now 2 decades old, and “may not reflect recent advances in cardiovascular disease prevention,” the investigators wrote.
Most studies in the area have been small and retrospective, they added, and have not adequately assessed emerging risk factors, such as prediabetes, which appear to play a relatively greater role in the development of heart disease among South Asians.
Methods and results
To address this knowledge gap, Dr. Patel and colleagues analyzed data from the UK Biobank prospective cohort study, including 449,349 middle-aged participants of European ancestry and 8,124 similarly aged participants of South Asian descent who did not have heart disease upon enrollment. Respective rates of incident ASCVD (i.e., MI, ischemic stroke, or coronary revascularization) were analyzed in the context of a variety of lifestyle, anthropometric, and clinical factors.
After a median follow-up of 11.1 years, individuals of South Asian descent had an incident ASCVD rate of 6.8%, compared with 4.4% for individuals of European descent, representing twice the relative risk (adjusted hazard ratio, 2.03; 95% CI, 1.86-2.22; P < .001). Even after accounting for all covariates, risk of ASCVD remained 45% higher for South Asian individuals (aHR, 1.45; 95% CI, 1.28-1.65; P < .001). This elevation in risk was not captured by existing risk calculators, including the American College of Cardiology/American Heart Association Pooled Cohort Equations, or the QRISK3 equations.
The findings were “largely consistent across a range of age, sex, and clinical subgroups,” and “confirm and extend previous reports that hypertension, diabetes, and central adiposity are the leading associations in this observed disparity,” the investigators wrote.
Two diabetes subtypes are more prevalent in South Asians
Hypertension, diabetes, and central adiposity do not fully explain South Asians’ higher risk for ASCVD, wrote Namratha R. Kandula, MD, of Northwestern University Medical Center, Chicago, and Alka M. Kanaya, MD, of the University of California, San Francisco, in an accompanying editorial published in Circulation.
Some of the undetected risk may stem from unique diabetes disease factors, Dr. Kandula and Dr. Kanaya added.
“Newer data have demonstrated distinct subtypes of type 2 diabetes, with South Asians having a higher prevalence of both a severe insulin resistant with obesity subtype and a less recognized severe insulin deficient subtype,” they wrote. “Importantly, both of these more prevalent diabetes subtypes in South Asians were associated with a higher incidence of coronary artery calcium, a marker of subclinical atherosclerosis and strong predictor of future ASCVD, compared to other diabetes subtypes.”