APOL1 Risk Variants Associate With the Prevalence of Stroke in African American Current and Past Smokers

African Americans face a higher stroke risk than other racial groups in the U.S., which is not fully accounted for by traditional risk factors or socioeconomic differences. Tobacco smoking, a well-established independent risk factor for stroke and responsible for one-fifth of all strokes in the US, has only recently been evaluated in this population. The 2.5 times higher risk for African American smokers compared to non-smokers, is even greater when contrasted with non-Hispanic Whites, highlighting the need to investigate the underlying reasons for this disparity.

In the cross-sectional study, Mustra Rakic and colleagues investigated the role of two clinically important genetic variants of apolipoprotein L1 (APOL1) in tobacco-related stroke. These variants are common among the African American population and very rare in people of other races. They studied 500 self-identified African American adults recruited through the UCSF Lipid Clinic, and discovered that participants who were current or past smokers and carry the APOL1 risk variants have higher odds of having a history of stroke. Tobacco smoking is suggested to act as a 'second hit,' alongside the genetic predisposition conferred by APOL1 risk variants. They also observed that carriers of two APOL1 risk alleles who have ever smoked tend to have highest odds for stroke, followed by those carrying one APOL1 risk allele who have ever smoked. The smallest odds are among those who have ever smoked but do not carry any APOL1 risk alleles. Given the high frequency of APOL1 risk variants in the African American population, (roughly 50% of African American people carry at least one risk allele), this study may offer an explanation, at least partially, to the excess burden of tobacco-related stroke in this population. If you are interested in finding out more, this work has been recently published in the Journal of the American Heart Association.