Covering a slatted base

Hi, I understand that you recommend covering a slatted base with sheets of mdf. I have a wooden bed which has sprung slats and I am wondering whether it would be better to cover the slats with mdf sheets or whether it would be better to replace the slats completely and create an mdf base for the mattress? I suspect this would potentially affect the mattress ability to breath and would somewhat affect the feel of the mattress? Having said that do divans usually have a solid base for the mattress to sit on? If so how would replacing the slats with mdf sheets on my wooden bed differ?
Thanks for your time,