For what it's worth, the dataset they used does in fact have measurements spanning 30 years of adulthood, and similar papers from that dataset leveraging the longitudinal data have found similar conclusions.
Why it happens is less clear. It could be stress effects, or it could be something like people with more social support are more likely to get help going in for preventative care etc.
Why it happens is less clear. It could be stress effects, or it could be something like people with more social support are more likely to get help going in for preventative care etc.