I was diagnosed with this many years ago after the consultant ruled out lots of other possible causes of a persistant cough. (TB, cancer, asthma, allergies etc etc).
It's damage to the very tiniest air tubes in the lungs.
He reckoned it might be due to having whooping cough very badly as an infant (in pre-vaccination days).
Said he was seeing it in an increasing number of folks my age who had whooping cough when young, and that the damage had always been there but didn't become troublesome until lung function naturally reduced with age.
(For a while I was on a proton pump inhibitor - not convinced it did any good, and when the formulation was changed and wrecked my innards I told them I'd rather put up with the cough!)
So the only advice really was to just reduce the irritation by sucking a boiled sweet, which is more effective than just drinking water.
It can get worse with strenuous exercise, especially in very cold weather, but quickly settles back to "normal"
It's irritating, and I no longer use hostel dorm accommodation due to irritating others.
But it isn't going to kill me.
Let me know how you get on, please.