Cognitive ability and functional status.

Significant confusion exists in the literature about functional status. Despite its importance, little attention has focused on developing and substantiating frameworks that detail the underpinnings of functional status, which has resulted in lack of agreement about its definition and dimensions. The purpose of this literature review was to examine the development of functional status and to describe the inclusion of its cognitive dimension. Cognition is one key dimension of functional status. One must 'know how' to perform to be successful in an activity. While cognitive capacity is generally considered in relation to functional status, the nature of the cognitive dimension is poorly described and poorly understood. Three databases were selected for review: Citations in Nursing and Allied Health (CINAHL), Psychology Literature (PsychLit), and the Medical data base known as MedLine. Key word searches identified thousands of sources. This analysis includes an extensive sampling of these sources from the 1960s through to 1998. The sources sorted into four primary categories and demonstrate a growing recognition of the cognitive dimension of functional status in the literature. Despite this recognition, the lack of conceptual clarity of both the term functional status and its cognitive dimension limits communication among disciplines and limits comparisons of functional status outcomes across studies. Functional status models are needed that include cognition as a core dimension. Population specific descriptions of the cognitive dimension should be guided by knowledge in the neurosciences.