HIPAA restrictions on researchers have affected their ability to perform retrospective, chart-based research as well as their ability to prospectively evaluate patients by contacting them for follow-up. A study from the University of Michigan demonstrated that implementation of the HIPAA Privacy rule resulted in a drop from 96% to 34% in the proportion of follow-up surveys completed by study patients being followed after a heart attack. Another study, detailing the effects of HIPAA on recruitment for a study on cancer prevention, demonstrated that HIPAA-mandated changes led to a 73% decrease in patient accrual, a tripling of time spent recruiting patients, and a tripling of mean recruitment costs.