Papers often make statements about the prevalence of the disease or condition being studied.  These statements may be specific to changes in the rate, such as:

“There has been a sharp increase in stomach cancer rates in people over the age of 50.”

or specific to the age group (or nationality or gender or other patient factor):

“Most people diagnosed with stomach cancer are between their late 60s and 80s.”

 But sometimes the statement is quite general.  In such cases, it is incorrect to say that the disease is “popular”.

 “Stomach cancer is more popular in men than in women.” (incorrect)

The word “popular” is used to describe something that many people like or want to have.  So we may describe a “popular fashion”, a “popular TV show”, a “popular song” because many people want to wear that fashion, want to watch that TV show or want to sing/listen to that song.  People enjoy these things. 

Disease is never popular.  No one ever wants to have a disease. No one ever enjoys being sick.  If we said that a disease is popular, it would suggest that the people who are sick are happy to be sick. 

So when we talk about a disease, we use the word “common”.

“Stomach cancer is more common in men than in women.”

This indicates that many people have the disease without suggesting that they enjoy being sick.