One of the reasons heparin, a blood thinner, was used for more severe Covid-19 infections was that the smallest arteries of the body, including the brain, tended to become clogged with products of the virus' effects on the body.
Blood vessel problems are more common in males, and arterial blood vessel disease of various types are a known risk factor for brain "aging", cognitive impairment and dementia.
This suggests the hypothesis that the "aging" effects of Covid-19 on the brain are mediated by effects of active Covid infection on small blood vessels.