Annual percent changes in NPC incidence stratified by sex in Sihui County, Guangdong Province, South China from 1987 to 2011 with Joinpoint regression. EAPC, estimated annual percent change. ^, P < 0.05. From 2003 to 2009, the NPC incidence for males significantly increased, with an EAPC of 6.8% (95% confidence interval [CI], 0.1%–14.0%). The EAPCs during other periods for both sexes were not significant.