A rise in reported cases occurred in the early 2000s: eight deaths from the syndrome in California in 2002 after three successive years of four deaths per year, and Schlievert's study found cases in part of Minnesota more than tripled from 2000 to 2003. Schlievert considers earlier onset of menstruation to be a cause of the rise; others, such as Philip M. Tierno and Bruce A. Hanna, blame new high-absorbency tampons introduced in 1999 and manufacturers discontinuing warnings not to leave tampons in overnight.