The system calculates a person’s “brain age” and compares it with their actual age. The larger the gap, the greater the observed dementia risk. The findings suggest that detailed patterns in sleeping brain activity may reveal changes that conventional sleep measurements miss. Previous research has found little connection between dementia risk and broad measures such as total sleep time, sleep-stage duration, and sleep efficiency. However, the findings do not establish that an older brain age causes dementia or that changing sleep patterns will necessarily prevent it.