How to politely say in a paper that most of the published research on a topic is by the same person? My field is cardiovascular epidemiology, and my current research question relates to some risk factor which is supposed to strongly elevate cardiovascular risk in a defined subgroup. However, my data do not indicate any such association, and power analysis shows that I have about 0.85 power to detect an effect of the size previously published. I see my findings as evidence for the null hypothesis.

Most of the available work on this risk factor in this subgroup comes from papers that all share one author. He is the leader regarding this question. He also holds a patent for assessment of this risk factor and possesses shares of a company that develops and plans to sell diagnostic tests to assess this risk factor.

I would like to make a statement in my paper that politely mentions these facts. This other author has published virtually everything there is that reports this positive association, and would profit enormously if it were true. However, I'm only a PhD student and they are top tier.

So how would I best go about this in my paper?
First off the fact that one group is dominating will be implicitly understood if you provide a paragraph or two summarizing their work and cite their publications. In such a paragraph you could add words like "ground-breaking" or phrases that describe the dominance of the group on the field. 

You could for example start the paragraph by saying: 


  "The work concerning risk assessment of [...] has largely been carried out by [the research group] (example citations)." 


(I hope you see the main idea of my attempt) Then you follow up on what they have done and cite their work.

It is just important to keep the tone as neutral as possible and let the citeable work speak for itself. Spending one or more paragraphs describing the work should be enough to make everyone understand the message.