Abstract
It is clear the number of chronic diseases increases with aging; however, it is not at all apparent clear how the interaction and combination of these diseases impact the longevity, functioning, and quality of life of older adults. A common method to address the impact of multiple diseases is to count the number of major diseases and examine their impact; however, this method lacks the specificity of including history and severity that could present very different pictures of outcomes. An alternative approach is to weigh diseases according to their severity and threat to mortality. This paper summarizes extant literature reviews of different measurement methods, highlights pilot studies to demonstrate their impact, as well as proffers a discussion of research directions to elucidate potential solutions.