Interesting research but very early stages. There's a good chance that this isn't really specific to bikes, but more generally applies to the benefits of people enjoying hobbies and a good quality of life translating into a better psychological state, which is known to affect health outcomes in a myriad of ways specially related to brain function and hormones.
Interestingly, the data also shows that mixed-walking is associated with reduced dementia as well... and I find it a bit confusing that the authors are lumping driving and public transit together in the nonactive category because public transit usually involves a good deal of walking too without people categorizing it as a walking mode of transport.
Beyond separating public transit from driving, I think major factors to control for are: 1) how often these non-commute activities happen; and 2) what's the stress level of that transportation mode. With those three things in mind I think it would clarify why would walking be associated with worst outcomes than nonactive...
Wait, this is a recent article? I (and Wikipedia) thought Vice has stopped publishing articles? (I aslo dimly remember them being bought by someone terrible but looks like I'm confusing that with something else)
Craigslist or Marketplace. Get a 90s mountain bike in your size. Start riding. Join a cycling club/social group. People are always changing bikes, and would be happy to let an older one go for a decent price.
It CAN be an expensive hobby, but it doesn’t have to be. I’ve been riding my $200 Craigslist special for about 1200km this year and I haven’t spent a penny on it.
Seconding bike co-ops, especially for people who don't know much or are intimidated by bike maintenance. The people who work at these places are always super eager to help you get on a good bicycle for cheap!
Used bikes on Craigslist, get a chromoly 3x7 from a reputable brand. They are super cheap, reliable, and versatile. My main commuter is just an old Trek 820 MTB with some minor upgrades I've made over the years.