The interaction between genetic and environmental factors are considered very important in the complex auto-immune diseases, among them rheumatoid arthritis.

The authors based their finding on the comparison of 115 post-menopause women with the disease and 466 women without arthritis, all of them participants in the Iowa Women's Health Study. The results revealed that tobacco consumption duplicates the probability of developing the disease in women who have not inherited most of the genetic risk factors established for the disease: HLA-DRB1. Quite the contrary, among those that do present/display these genetic factors, tobacco consumption does not influence the disease in a significant way.