Objective:To investigate the effect of cumulative serum uric acid (cumSUA) on early-onset ischemic stroke in young adults.Methods:A prospective cohort study was conducted. A total of 15 607 Kailuan workers who participated in at least two physical check-ups in 2006 and 2008 and at the time of the last physical check-up before 2014 were selected as subjects. Cumulative uric acid exposure during the follow-up period was calculated. The subjects were divided into three groups according to the quantile of cumSUA: the first quantile group was cumSUA<1 563 μmol/L·year, the second quantile group was: 1 563 μmol/L·year≤cumSUA<1 996 μmol/L·year, the third group was cumSUA≥1 996 μmol/L·year. The time of the last physical check-up was regarded as the starting point of follow-up, and early-onset ischemic stroke was regarded as the end event. Kaplan-Meier was used to calculate the incidence of early-onset ischemic stroke in different groups, and Log-rank method was used to calculate the differences in the incidence of early-onset ischemic stroke among different groups. Multivariate Cox regression model was used to analyze the risk of early-onset ischemic stroke in different groups. A four-node (5th, 25th, 75th, 95th percentile) restricted cubic spline plot was used to assess the dose-response relationship between cumSUA and early-onset ischemic stroke.Results:A total of 15 607 subjects were followed up for (7.3±1.1) years. 100 cases with early-onset ischemic stroke were observed with an average age of (46±4) years old. The number of events in the first, second, and third quartile groups was 18, 35, and 47, respectively, and the cumulative incidence rates in the first, second, and third quartile groups were 0.40%, 0.77%, and 1.07%, respectively. The difference in cumulative incidence of endpoint events between the groups was statistically significant by Log-rank test ( χ2=14.96, P=0.003). The results of Cox regression analysis showed that after correcting for confounders, the HR(95% CI) for early-onset ischemic stroke in the second and third quartile groups was [1.67(0.92,3.00), P=0.090; 2.05(1.48,3.69), P=0.020]. Restricted cubic spline results showed a nonlinear correlation between cumSUA and early-onset ischemic stroke after adjysted for confounders. Conclusion:Cumulative serum uric acid is positively correlated with the risk of early-onset ischemic stroke in young adults.