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We welcome Ackland et al’s timely discussion on the terms “non-communicable” and “chronic” disease.1 Their argument is that conditions currently labelled “non-communicable” are in fact “communicable” because the risk behaviours that underlie them are highly transmissible. Thus they argue for a change in label, from “non-communicable diseases” to “chronic diseases”.
Their argument, however, confuses one classification system, which is based on cause (namely, communicable diseases compared with non-communicable diseases compared with injuries), with a second classification system, which is based on effect (namely, acute conditions compared with chronic conditions). Their argument also overlooks the growing consensus that chronic conditions include certain communicable diseases, such as HIV/AIDS.2,3 In fact, certain non-communicable conditions are acute in nature, while certain communicable conditions require chronic, ongoing care. For example, HIV/AIDS clearly has an infectious aetiology but requires long term management by the healthcare system. As such, it has a great deal in common with type 2 diabetes. Conversely, acute appendicitis is a “non-communicable disease” that requires an urgent health care response quite similar to bacterial meningitis.
A comparison has been made of the burden of disease in sub Saharan Africa using the current global burden disease study broad classification system (three cause based groups, of which non-communicable diseases is one) and an alternate classification based on the effect based groupings of chronicity or acuteness.4 The overall patterns in children aged under 5 are similar with both classification systems, but in people aged over 5 there are noticeable differences. For example, 35% of disability adjusted life years (DALYs) were attributable to non-communicable diseases, but 86% were attributable to chronic conditions, reflecting in particular the impact of HIV/AIDS and TB.
A classification system should first and foremost be internally consistent, and beyond this it should also serve the needs of those using it. Whereas basic clinical researchers will probably be best served by using a cause based classification system, an effect based classification system is likely to be of greater utility to health system planners. Conditions requiring long term care, whatever their aetiology, place similar demands on healthcare systems, patients, their families, and communities. We argue strongly that the term “chronic” will be more readily understood and of greater utility if it refers to conditions requiring long term management by health systems.
The letter by Unwin et al in response to our paper1 makes some important points about the attributes of disease classifications. We agree that, unfortunately, it is commonplace for classifications based on cause and those based on effect, to be interchanged by the public health community. This not only causes confusion in the minds of public health policy makers, but promotes bureaucratic apathy towards resourcing prevention programmes for diseases that contribute so significantly to the burden of disease. Why would a jurisdiction dedicate scarce resources towards preventing and controlling diseases that are long term (chronic) and where causation is unclear (non-communicable)? Many jurisdictions will only take on the concept of an epidemic seriously when there is a clear link to the traditional concept of “communicable” or infectious disease.
So it is very important to encourage use of language in describing diseases that is of practical value to both clinical researchers and policy makers. This language should engage everyone in thinking about public health responses to diseases from both the perspectives of disease prevention and disease control. While international classification systems are unlikely to change quickly, we are seeking a shift towards more appropriate use of terminology when describing major disease states.
Our desire is to encourage people to think about the upstream issues of causation of diseases in order to motivate a more pragmatic focus on public health interventions. Indeed we support use of the term “chronic” to emphasise the long term implications for the health system, but more importantly wish to discourage use of the term “non-communicable” where there is mounting evidence for the non-microbial, communicable nature of many chronic diseases. Qualifying some chronic diseases as being “transmissible” may be helpful in highlighting the role of social, cultural, and societal factors as disease vectors. Herein lie the opportunities for improving public health responses and interventions. We are glad that Unwin et al support our thinking to promote the use of the term “chronic” to denote conditions requiring long term care, which is more readily understood by the public health community.