The condition, called Transient Global Amnesia or TGA, is something of a mystery that research has yet to find an answer to. It comes on suddenly and unexpectedly and can be triggered by a cold winter swim.
Dag Nyholm is professor of neurology at Uppsala University and senior physician at the University Hospital.
– It’s a bit of a strange condition. Suddenly you lose your orientation. People usually ask questions about what day it is today. During that time, you can’t imprint new memories, they don’t stick. But you remember everything else. You can drive the car and find your way home.
It is unclear what this is due to
According to Dag Nyholm, it is common for a person affected by TGA to get stuck and ask the same question over and over again. Long-term memory works as usual and you recognize your relatives, but you cannot learn new things.
– We don’t really know what is happening. It seems that there is some kind of error in the memory center of the brain. There are various theories that there is some nerve influence. It can also be a blood vessel effect, so that there is temporarily poor circulation in the memory center. It’s still tricky.
The symptoms come on suddenly and last for a while, often between four and five hours, but can last up to a day.
– It’s a bit like a migraine. There can be neurological symptoms with migraine, it is common to have visual field effects. There may be lightning in the field of vision. TGA is much like a migraine, but usually only comes once in a lifetime. But you can get migraines often.
It is unusual to be affected by TGA and once you have had it, there is little risk of getting it again, which makes it even more difficult to study.
– It is so difficult to research it, it appears suddenly and goes away, says Dag Nyholm.
Can be triggered by hard exercise or sauna bathing
In 2023 one came study done by researchers at the University of Kuopio in Finland, where it was estimated that there are 18 cases of TGA per 100,000 life years across the entire population. But the majority of those affected are over 50 years old. In the age range 65 to 70 years, the proportion was 64 per 100,000 life years.
– There is an increased risk with age, but otherwise there are no clear connections. There are reports that it is more common after stress or heavy physical activity. Or in case of large temperature changes such as during winter bathing or sauna bathing. Any such stress impact. But it doesn’t have to be, it can also just appear.
The researchers suspect that more people suffer from TGA than is known so far, and Dag Nyholm advises anyone who suffers from sudden memory loss to seek medical care.
– What we do is investigate and see that it is nothing else. It could be some other disease that causes confusion and memory loss. It could be something strange in the brain or an infection.
But he doesn’t think winter bathers need to feel worried.
– If we discover that it is not another fault with the nervous system or a fever, then it is TGA and then it is very harmless.