To be honest I don't think there is enough information to even say it is bad science we just don't know.

My concern is (and I have seen this happen before) that there were likely media attending that conference and they love to pick little bits of data like this (without context) and sensationalise them particularly when it is an otherwise slow news day.

I can easily imagine the headlines "Most Commonly Used Diabetes Drug Causes Dementia".

The end result may be that people stop taking it in fear of dementia with the irony that poorly controlled diabetes is one of the biggest risk factors for dementia.