Best social network to cater to an old audience?

Older audiences are growing larger and larger as time goes, especially in the 40-50 years old frame, and albeit not as prominent as the 30< years old batch of web users, it's still a nice market to cater to thanks to the diversity of interests and the availability of their favourite niches (with health on top of the list)

What social medias, in your opinion, would be the best one to cater to older audiences?