Photo: Image of obese woman living in township in South Africa (Photograph by Silvia Landi)

One interesting insight that came up during analysis of a particular citation network was observed in the shape of the network. For example, it may provide information about how research evolves and how key articles shape the field (see here for more).

In this case, while looking at early articles in the network, it was noted that one early paper was not widely cited upon its publication, but later gained relevance in recent years. This gave a clue that the subject of research in this early article has become, once again, important in modern day.


Diabetes and MDR-TB

In 2001, Bashar and colleagues published a paper describing the incidence of multi-drug resistant tuberculosis and diabetes in a New York hospital over a 10-year period from 1987-1997. This was one of the earlier influential descriptions of the relationship between MDR-TB and diabetes. Although the relation between diabetes and tuberculosis had been described in the 80s and 90s, whether co-morbidity with diabetes increased the risk of drug-resistant tuberculosis was not as well known.

The citation network shows that the paper by Bashar was cited early on, and was followed up by authors such as Loddenkemper and Ferrara around that time (on the other hand Park and Frieden are articles cited by Bashar). After a decade, the paper was picked up by more recent articles from 2011 onwards, as seen at the top right of the network. The diagonal directionality of the network suggests that the field is moving away from research areas at the bottom left of the network towards subjects studied at the top right of the network. This happens to be diabetes and multi-drug resistant tuberculosis, among others. For example, the paper by Perez-Navarro LM in 2017  showed that Type 2 Diabetes contributed substantially to the presence of MDR-TB in a cohort studied in Mexico.

Thus, the work carried out by Bashar et al. was, in a manner of speaking, ‘ahead of their time’ and will be increasingly relevant in a world where diabetes is on the rise. By looking at the citation network, one could therefore determine the key influencer of a research area and also identify what that upcoming research area is about.

With the rapid onset of lifestyle-induced chronic illnesses, the co-morbidity between tuberculosis and diabetes is becoming an important risk factor towards the rise of multi-drug resistant tuberculosis. Though the mechanisms are unclear, diabetes may result in an immunological defect that result in less effective bacterial clearance during therapy, which may subsequently result in the development of resistant strains.

Furthermore, this observation, highlights clearly the important issue pertaining to the rapid rise of chronic diseases before the fight against infectious diseases has been truly won. The simultaneous co-existence of infections such as tuberculosis, Zika or Ebola with degenerative diseases will become increasingly a challenge in the developing world as seen in South Africa, a country heavily affected by AIDS and tuberculosis whilst simultaneously battling with the highest obesity rate in sub-Saharan Africa.