Complex sentence: Reisberg developed the caregiving assessment tool known as "FAST" (Functional Assessment Staging Tool) in 1988 which he claims allows those caring for AD patients to evaluate the stage of progress and symptoms throughout the disease.
Split into simpler sentences: Reisberg developed the caregiving assessment tool known as "FAST" (Functional Assessment Staging Tool) in 1988. This allows those caring for AD patients to evaluate the stage of progress and symptoms throughout the disease.