Barriers to clinical research participation in a diabetes randomized clinical trial.

Little is known about how barriers to research participation are perceived, affected by or interact with patient characteristics, or how they vary over the course of a clinical trial. Participants (285) in the Renin-Angiotensin System Study (RASS), a randomized clinical primary prevention study of diabetic nephropathy and retinopathy at 2 Canadian and 1 US university, rated potential barriers to research participation yearly for 5 years. Baseline barriers rated as most adversely affecting participation were: missing work; frequency of appointments and procedures; study length; number of appointments and procedures; access to study location; and physical discomfort associated with procedures.