Viewing for more than two hours daily kills your grey matter, a US study shows.
And Britons on average spent five hours and 40 minutes watching TV or videos every day last year, Ofcom found.
Each extra hour of TV seen by those aged 30 to 50 was linked to a 0.5 percent drop in brain size in the study, published in Brain Imaging And Behavior.
Lead author Dr Ryan Dougherty of Johns Hopkins Bloomberg School of Public Health in Baltimore said excessive viewing could be “targeted and reduced” for middle-aged people.
He said they are vulnerable to the “neurobiology of dementia and brain atrophy”.