Correlation is not causation...
True. But, if you live near a wooded area, or a body of water, go there, what do you notice ?
Cleaner air, less stress, appreciation for mother nature ?
IMO
And if that green space is, for example, Central Park ?
It's likely true that living near such properties does not PROTECT one from strokes, it seems to me that CHOSING to live near such properties can reflect a lifestyle that is less prone to strokes.
It's true that correlation is not causation, but it could very well be true that causation can create the correlation.