“I wonder whether it is isolation or a negative perception of solitude that is the issue”
I am glad you are asking this question.
However, I think there is a better question to ask.
The question is.
Do people who are more isolated have something wrong with them that makes them isolated and they die (suppose they have a disease that causes fatigue, or they have no money and can’t dress or act properly).
Or is it that People who are otherwise healthy, happy, and have money and clothes but choose to be alone are unhealthy and die of choosing to be alone.
Put it another way. If you have no money and can’t go out much do you die of no money or do you die of being more alone.
I think part of the issue is that if you’re alone there’s no one to make you take your pills or call 911 or make a doctor appointment for you when you’re sick, which is the sort of thing wives do. But I also think there is a healing effect in the contact with other people. Even physical touching, like a hug, has a healing effect.