The phrase "a direct relation to" is correct and usable in written English.
It can be used when discussing a clear and straightforward connection or association between two or more things.
Example: "There is a direct relation to the amount of exercise one does and their overall health."
Alternatives: "a direct connection to" or "a clear link to".
The new vision of cancer as natural phenomenon (programmed death of the organism) has a direct relation to current research, particularly to choosing directions of future investigations and treatment strategies.
Obviously, this has a direct relation to what's going on.
Stadiums are often referred to as domes, a direct relation to religious architecture".
I think it has a direct relation to divorce and its prevalence today.
He became reclusive, declining to receive even distinguished visitors unless they had a direct relation to his work.
"But I don't think there's any doubt that how they judge Iraq will have a direct relation to their judgment of me".
Building on surveys, focus groups, and analyses of issue network websites, Carpenter concludes that network access has a direct relation to influence over how issues are ranked.
In Great Britain, on the other hand, virtually no deductions are granted that do not in some measure bear a direct relation to the production of earned income.
To help engineers use digitization practically and efficiently, this paper proposes a method based on manufacturing case data that has a direct relation to manufacturing operations.
The losses in the stored potatoes have a direct relation to the intricate coupled transport phenomena of heat, mass and momentum transfer therein.
And it is staging Bellini's "I Capuleti e i Montecchi" and Handel's "Giulio Cesare in Egitto," both of which field Shakespearean characters (Romeo and Juliet, Caesar and Cleopatra) without having a direct relation to the plays.
