Patel A, Wang M, Kartoun U, et al. - Summarized by David L. Brown, MD

It is well-recognized that individuals of South Asian ancestry appear to be at exceptionally high risk for ASCVD compared with those of European ancestry. However, the magnitude of that risk and whether that risk is due to traditional or unidentified risk factors remain unknown. This study analyzed data from the UK Biobank, a prospective study that enrolled >500,000 individuals between 2006-2010. Within this cohort, 481,542 reported South Asian or European ancestry. Another 24,069 individuals with ASCVD diagnosed before enrollment were excluded, leaving 457,473 subjects for analysis. Biomarkers were assessed at the time of enrollment and other clinical conditions and risk factors were obtained by self-report.

A diet score was computed to estimate the degree of unhealthy eating habits. The primary endpoint was ASCVD defined by review of hospital records. Over a median follow-up of 11.1 years, corresponding to 5.0 million person-years of follow-up time, 554 of 8,124 (6.8%) individuals of South Asian ancestry experienced an ASCVD event compared with 19,756 of 449,349 (4.4%) individuals of European ancestry, corresponding to an adjusted hazard ratio (HR) of 2.03 (95% CI, 1.86-2.22; P<0.001). The observed higher risk of ASCVD in South Asian individuals was mitigated by inclusion of various risk factors as covariates in the Cox proportional hazard models.

Although each risk factor when added alone as a covariate to the Cox regression model did not significantly alter the risk estimate, when all the risk factors were sequentially added to the model, the collective HR estimates decreased to 1.45 (95% CI, 1.28-1.65; P<0.0001). The residual unexplained risk after correction for known clinical, anthropometric, lifestyle, and socioeconomic risk factors suggests underlying genetic causes. Importantly, despite this higher risk, there was no significant difference in predicted 10-year risk of ASCVD for individuals of South Asian and European ancestry predicted by American College of Cardiology/American Heart Association (ACC/AHA) PCE or the QRISK3 score. This study confirms recent ACC/AHA guideline recommendations to consider South Asian ancestry as an ASCVD risk-enhancing factor.