I wouldn't even show up in the kind of data they used:
"We, therefore, investigated data from nearly 500,000 people from the UK Biobank, with a mean age of 57. People were classified as socially isolated if they were living alone, had social contact less than monthly and participated in social activities less than weekly."
"Our study also included neuroimaging (MRI) data from approximately 32,000 people. This showed that socially isolated people had poorer cognition."
They focused on older people, severely isolated, for whom brain MRI data was available.
If you're not already having some sort of brain problem, you won't be listed in a database where your brain MRI data is available. "People with brain MRI data" is biased toward cognitive problems.
"We, therefore, investigated data from nearly 500,000 people from the UK Biobank, with a mean age of 57. People were classified as socially isolated if they were living alone, had social contact less than monthly and participated in social activities less than weekly."
"Our study also included neuroimaging (MRI) data from approximately 32,000 people. This showed that socially isolated people had poorer cognition."
They focused on older people, severely isolated, for whom brain MRI data was available.
If you're not already having some sort of brain problem, you won't be listed in a database where your brain MRI data is available. "People with brain MRI data" is biased toward cognitive problems.