Does ethnicity alter the hazard of stroke in patients with major modifiable cardiometabolic risk factors? A population-based longitudinal study using electronic health records in South London

Ethnic inequality in stroke risk was partially explained by a history of hypertension, diabetes and socioeconomic status. We aimed to estimate the impact of ethnicity on the hazard of stroke in patients with hypertension, diabetes or hypercholesterolaemia in an urban, multiethnic, youthful and deprived population. Multistate models were constructed using electronic health records, including the date of stroke onset, stroke risk factors, and the Index of Multiple Deprivation in Asian, Black or White adult patients registered at 41 general practices in South London between 2005 and 2021. Transitions to hypertension, diabetes or hypercholesterolaemia (transition 1), and from these cardiometabolic risk factors to stroke (transition 2) were considered. The study included 651,888 of the 849,968 registered patients (76.7%), of whom 8.6% were Asian, 18.2% Black, and 73.2% White, while 54.1% were female. Among Black patients, 2.1% had a recorded stroke, compared with 1.2% of Asian patients and 1.0% of White patients. Compared to White patients, Asian and Black patients had generally a higher risk of transitioning to hypertension, diabetes or hypercholesterolaemia (transition 1). Ethnicity however, did not affect transition to stroke from cardiometabolic risk factors (transition 2), except for hypercholesterolaemia, where Black patients had a higher risk of strokes. Our results confirm that Black ethnicity does not confer excess hazard of stroke in patients with hypertension or diabetes. This observation was also made for Asian ethnicity. An excess hazard of stroke associated with Black ethnicity was observed only in patients with hypercholesterolaemia.