The 'interest rate' on servicing the debt is important as it will make if harder/easier to reduce the ratio or just pay the interest.
Looking at a UK debt to GBP chart, we were paying off a lot of WW1 and WW2 debt, 250% ratio in 1946!, until the 1970's, and debt to GDP stayed between 20 and 50% until 2009 and has been mostly going up since.