Among all of the barriers to study participation, economic factors and time constraints are the most powerful and difficult to overcome. For some, but not all, monetary remuneration was an important motivator for participation. For many, flexible scheduling was a key to participation regardless of remuneration, given that this study required approximately 8 hr to complete the in-home and MRV-based portions. Including weekends and evenings among the examination times facilitated the participation of individuals who could not take time off from work or childcare responsibilities during regular workdays.
