The published research is usually the other way around, that is "who reads what?", not "what is read by whom?". The best researched group of readers is children and adolescents. Results are usually broken down by age and sex, sometimes by socio-economic status. The next best reseached group are women. You can find studies for both groups by using Google Scholar. If you are lucky, some journalist has condensed the findings for you in an article that you can find through Google.
There are some genres that have been researched for their readership (e.g. pulp novels about doctors [I'm not making this up]) or certain occupational groups (e.g. nurses [I'm not making that up either]) but by and large there is no research that is as specific as what you expect, listing genres by the occupations of their readers.
There are companies like Nielsen who collect detailed readership analyses, and you can access their data if you are willing to pay a couple of hundred dollars. There are also publisher's interest groups that conduct that kind of research and make it accessible to their member companies. Sometimes some of these findings get reported in the media, so you might find something through Google.
Your options as a writer are to go to forums relevant to your genre and find who is interested in it. You could open a thread and ask for background info. Or you can create an app on Facebook and target it to people "liking" a specific genre and then collect info on the users that interact with your app. I did that once for teens who read fantasy. I wanted to find out what else they "like". Or, if the complementary perspective interests you, you can approach people of a certain occupation, eithet online or in person, and ask them what they read. And so on, you get the idea.
I personally don't believe that graphic designers read fantasy. I know a few and they all do not read books at all. If you find information on the net, make sure you understand how that information was uncovered and who publishes it for what reason. Stuff on the web is often made up or anecdotal. You'd do well to distrust it.