Background:The risk of prehypertension with dynamic change in waist circumference (WC)has not been investigated before.Methods:A total of 4848 participants who underwent health check-up in Beijing Health Examination Center and Beijing Xiaotangshan Hospital were recruited in 2009 and followed up in 2016.Participants were classified into four groups according to categories of percent WC gain:≤ -2.5%,-2.5% to 2.5%,2.5% to 5% and > 5%.Modified Poisson regression models were used to evaluate the effect of WC gain on prehypertension.Results:During 7 years of follow-up,we identified 2492 prehypertension events (1378 women).Compared with participants without abdominal obesity at both baseline and follow-up,participants who developed abdominal obesity or stayed abdominal obesity at follow-up were at greater risk of prehypertension.Compared with WC gain ≤ -2.5%,participants with WC gain had higher risk for prehypertension for men (WC gain (2.5%-5%):RR=1.16,95% CI:1.02-1.32,WC gain (>5%):RR=1.25,95% CI:1.10-1.42) and women (WC gain (>5%):RR=1.32,95% CI:1.17-1.49).Conclusions:The risk for prehypertension increased significantly with increasing WC for both genders in Chinese population.Lifestyle interventions aiming at preventing abdominal obesity are urgently needed to reduce the increasing burden of prehypertension,hypertension and its complications.