Silent stroke is stroke that does not have any outward symptoms, and people are typically unaware they had experienced stroke. Despite not causing identifiable symptoms, silent stroke still damages the brain and places the person at increased risk for both transient ischemic attack and major stroke in the future. Conversely, those who have had major stroke are also at risk of having silent stroke. In a broad study in 1998, more than 11 million people were estimated to have experienced stroke in the United States. Approximately 770,000 of these were symptomatic and 11 million were first-ever silent MRI infarcts or hemorrhages. Silent stroke typically causes lesions which are detected via the use of neuroimaging such as MRI. Silent stroke is estimated to occur at five times the rate of symptomatic stroke. The risk of silent stroke increases with age, but they may also affect younger adults and children, especially those with acute anemia.