What are white spots on the brain and do they increase the risk of dementia?

White spots on a brain scan are areas in the white matter that appear brighter than normal on MRI. They are a sign that the small blood vessels in the brain have been damaged, for example by high blood pressure or ageing. Small, scattered spots also occur in healthy young people and are not necessarily a cause for concern in that context. Only larger or more extensive spots in specific locations are clearly linked to disease and increased risk.

Yes, pronounced white spots significantly increase the risk of dementia. A meta-analysis of nine prospective studies found that people with extensive spots have nearly twice the chance of developing dementia later in life. The same research showed that the risk of stroke is more than three times as high, and the risk of premature death is twice as high. These are associations, not proven causal relationships.

In vascular dementia, a form of dementia caused by poor blood flow to the brain, the spots are particularly pronounced. A meta-analysis of fifteen studies involving more than 4,000 patients showed that people with this type of dementia have significantly more and larger spots than people with Alzheimer's disease or without memory complaints. The researchers note the possibility of bias in the available studies.

White spots can also grow larger over time. In people who already have many spots, the volume can increase by a quarter per year. This growth is associated with further decline in cognitive function, particularly in processing speed and planning tasks. A small study of 86 people also found that spots in specific locations, such as the temporal lobe, are associated with memory problems in particular. This last finding warrants confirmation in larger research.

At a biological level, research points to a downward spiral: ageing damages the insulating layer around nerve fibres, the repair of that layer deteriorates, and this can drive inflammation and further brain damage. This mechanism is plausible but has not yet been fully proven in humans. If a scan has revealed spots, discuss their extent and location with your doctor: not every spot calls for the same course of action.