You think that preventing a STD, or a tick bite wouldn't count as a lifestyle change?, really?.
I think the point is more that people already try to not get HIV / AIDS - and once they have it, they can't just "get rid of it".
The article is about lifestyle _changes_ you can make to mitigate existing risk factors. You can't _change_ whether or not you have AIDS once you already have it, not yet at least.
And if you make a _special_ effort to avoid getting AIDS because it has a minor impact on your risk of getting dementia in old age... your priorities are WAY out of whack.