Abstract
Most aging patients have multiple concurrent health problems. However, most current medical practice and research are largely based on a single disease model, failing to account for the simultaneous presence of multiple conditions. Clinical trials, practice guidelines, and pay-for-performance schemes may thus have limited applicability in older patients. We report on the 2005 American Geriatrics Society/National Institute on Aging conference on Comorbid Disease and Multiple Morbidity in an Aging Society. The two-day conference was designed to clarify concepts of multiple concurrent health conditions; explore implications for causation, health, function and systems of care; identify important gaps in knowledge; and propose useful next steps. While the conference did not attempt to standardize terminology, we here develop the concepts of comorbidity, multiple morbidity, condition clusters, physiological health, and overall health as they were used. The present report also summarizes sessions addressing the societal burden of comorbidity, and clinical research on particular diseases within the framework of comorbidity concepts. Next steps recommended include continuing clarification of terms and conceptual approaches, consideration of developing and improving measures, as well as developing new research directions.