Humm, that is interesting. Our son had a lot of problems with ear infections as a young child. Perhaps that is when we were told about the risk of unrecoverable hearing loss and assumed that the 'use it or loose it' was a lifetime process.
I suspect that my husband has had a mild hearing loss all his life as he often miss-pronounces words. He doesn't seem to distinguish some vowels.
Get him to an Audiologist... you might find out he just isn't listening to you
I wonder if the fact that we live in an area with hills tall enough to manifest pressure changes in short time frames contribute to this problem because small children can't 'pop their ears'.
Probably not, community environmental concerns like air pollution can play a part though.