If you have noticed that you can’t remember things like you used to, you may be accumulating lesions in your brain, caused by tiny silent strokes, according to a recent study in the journal Neurology. These lesions are small regions of dead brain cells. The research links the accumulation of these lesions to memory loss in one of four healthy older people. Other studies found an association between these silent strokes and an increased risk of stroke later in life.
Silent strokes
Silent strokes are little strokes that you are not aware of, because there are no symptoms. These silent strokes cause lesions, also called infarcts, consisting of dead brain cells. Most of the small infarcts are created by blockage of tiny blood vessels in the brain. The blockage deprives brain cells of nutrients and oxygen, causing the brain cells to die. Silent strokes increase your risk for future strokes and now have also been linked to gradual loss of memory.
Memory loss
Researchers wanted to know if the damage caused by silent strokes or other factors affect memory. Using MRI (Magnetic Resonance Imaging), they scanned the brains of 658 people, who were 65 and older, healthy, and free of dementia. They tested individuals for memory, language, and processing information. The brain scans determined that 174 people had evidence of silent strokes. The people with silent strokes did worse on memory tests than people without silent strokes.
Risk factors
An analysis of 2040 women, age 62 +/- 9 years, in the Framingham offspring study found that 11 percent of women had suffered a silent stroke. The study also looked at risk factors associated with the incidence of silent stroke. The Framingham offspring study and other studies found that most risk factors for silent stroke are the same as for other kinds of strokes:
High blood pressure High levels of homocysteine in the blood (Framingham offspring study) Irregular heart beat (Framingham offspring study) Smoking Diabetes Heart disease Genetic predisposition
Stroke, dementia, and Alzheimer’s disease
Silent strokes are risk factors for subsequent strokes and dementia. In a 2007 review of silent strokes and resulting brain infarcts in the medical journal Lancet, the authors write: “Moreover the presence of silent infarcts more than doubles the risk of subsequent stroke and dementia.” Because Alzheimer’s disease is primarily associated with memory loss, the recent study on silent strokes can help us better understand Alzheimer’s disease and may lead to solutions for memory loss.
Sources
Blum, S. et al. Memory after silent stroke: Hippocampus and infarcts both matter. Neurology (2012) 3, 38
http://www.sciencedaily.com/releases/2011/12/111229092038.htm
http://www.ncbi.nlm.nih.gov/pubmed/17582361
http://www.ncbi.nlm.nih.gov/pubmed/18583555