Use Your Words Carefully: What Is a Chronic Disease?

One important element of effective communication is having a shared language or at least a shared understanding of the meaning of the central words used in a conversation. One term that is often used in discussions between patients and medical providers, in the academic literature, and in policy discussions, is “chronic disease.” There is not only tremendous variation in the diseases that are included under the umbrella term “chronic disease” but also variation in the time a disease must be present for something to be referred to as chronic. Furthermore, there is a move to include chronic conditions that are not indicators of disease, but long-standing functional disabilities, including developmental disorders and visual impairment (1–4). Within professional communities (i.e., medical, public health, academic, and policy), there is a large degree of variation in the use of the term chronic disease. For example, the Centers for Disease Control (CDC) classify the following as chronic diseases: heart disease, stroke, cancer, type 2 diabetes, obesity, and arthritis (5). The Centers for Medicare and Medicaid Services have a more extensive list of 19 chronic conditions that includes Alzheimer’s disease, depression, and HIV, to name a few. This difference, within the Department of Health and Human Services alone, although not surprising to those in the field, has the potential to create confusion and misunderstanding when speaking in generalities about the impact of chronic disease, the cost of chronic disease, and overall measures to reduce chronic disease. The academic literature is not immune to the same kind of terminology variation. Differences in how “chronic disease” is used are largely dependent on the data used for the research and the discipline of the lead authors (i.e., public health and sociology). For example, one study, authored by individuals from Harvard Medical School, explored the prevalence of chronic disease using NHANES data (1999–2004). The study classifies the following as chronic diseases: cardiovascular disease, hypertension, diabetes mellitus, hypercholesterolemia, asthma, COPD, and previous cancer (6). Another academic study on chronic disease, authored by a geriatrician, classifies chronic illness as “conditions that last a year or more and require ongoing medical attention and/or limit activities of daily living” (7). The implication of a non-uniform use of the term is that a detailed read of each study is necessary to avoid erroneous conclusions regarding interventions necessary to reduce chronic disease burden for the individual and society. Popular Internet sources used by the general public to gather medical information use the terms “chronic disease” or “chronic condition” to mean slightly different things. For example, MedicineNet describes a chronic disease as,