Orthostatic intolerance: a frailty marker for older adults.

To the best of our knowledge, this is the first study defining OIS as symptoms both self-reported and provoked during the test, and showed a strong correlation between OIS and frailty. OIS may be defined as a multifactorial and independent marker for frailty, regardless of OBPC. Further prospective investigations are warranted to support the relationships between OIS and frailty.