York University researchers, led by Akinkunle Oyeyemi, analysed data from millions of adults aged 35 and older; the study appears in PLOS One.
The report says sitting more than eight hours a day is an independent risk factor, as exercise alone does not fully offset harms linked to metabolic slowdown, insulin resistance and poorer blood sugar control.
It comes as South Korea estimates 970,000 dementia patients aged 65 and older in 2025, topping one million in 2026, with mild cognitive impairment projected to exceed four million by 2033.
My office job requires hours of sitting. Is my brain's future at risk even if I exercise daily?
If exercise can't erase sitting's harm, what simple two-minute habit can actually protect your brain?
How Sitting More Than 10 Hours a Day Raises Dementia Risk and What You Can Do About It
Overview
Recent research shows that prolonged sedentary behavior, especially passive activities like watching TV for over 10 hours a day, significantly increases dementia risk by reducing blood flow and oxygen to the brain. This leads to vascular dysfunction, inflammation, and brain cell damage, which together raise the chance of cognitive decline. People carrying the APOE-e4 gene are more vulnerable to these harmful effects. However, regular physical exercise, adequate sleep, and replacing passive sitting with mentally active tasks can lower dementia risk. Practical solutions like wearable technology and workplace changes help reduce sitting time, offering promising ways to protect brain health and prevent dementia.