Diversity, equity and inclusion are getting quite a bit of attention so you might be able to capitalize on that interest.
Consider a paper describing the patient population your studies recruit from. Take a look at how recruiting is done, the demographics of those who inquire about the study, those who are informed, those who sign the consent, and those who make it through screening to the intervention itself (if applicable). Does each group reflect the characteristics of the underlying population of people with this condition or are there points in the process where the sample becomes non-representative of the underlying population? The entire study of this kind can be done as a look back at existing data.
Beyond age, race, sex, consider education and socioeconomic status (zip code can be a proxy in some locations for economic status).
What other studies have done this exercise in other locations or with other health conditions (literature review)? Where are the points that need an increase in effort to recruit and retain a representative sample of the target population? What might those efforts be?