What type of people are affected by Rheumatoid Arthritis?

What people are affected by Rheumatoid arthritis. Like wht king of group? (african americans, whites, eastern) Can you please help me? This goes to an project and i searched and searched everywhere and i couldnt find the answer =( also do you knw the number of people that are affected by this? Like how many people in the world are suffering with this joint inflammation?