In fact, sex is just one of the activities that can cause a rare condition called "transient global amnesia." The ailment has no known cause — though there are a few theories — and usually lasts for a fairly short period of time. In the case of the Georgetown woman, the symptoms began to clear up after she'd undergone a few tests in the hospital. Like other patients with the condition, her brain had suffered no damage, and her difficulties were only with forming new memories rather than recalling what had happened to her before the mind-wiping sex.
Why would sex cause a temporary memory loss? The main theory is that the way people exert themselves during sex — basically, using muscles in their lower abdomens — can cause a temporary glut of de-oxygenated blood in the brain.
Most of you can call it humbug but its true. This problem usually shows itself after 50 when the sex gets more mind boggling.
So Beware!