According to the CDC, nearly 1 in 2 U.S. adults have hypertension, Richland County Health Department Prevent. Promete. Protect. yet only 1 in 4 have it under control. According to the CDC, nearly 1 in 2 U.S. adults have hypertension, Richland County Health Department Prevent. Promete. Protect. yet only 1 in 4 have it under control.