Sex has many benefits, including reducing high blood pressure, improving the immune system and aiding better sleep.The act of sex and orgasm releases a hormone that is important in building trust and bonding between people.There's a dark side to this: people die after sex. The incidence is very low and accounts for a small percentage of sudden deaths.There are a lot of reasons why this happens. Most of the time, it is caused by the physical strain of the sexual activity, or prescription drugs, or illegal drugs.As people age, the risk of sudden cardiac death increases. A forensic postmortem study from Germany found that a small percentage of sudden deaths were related to sexual activity.The most frequent cause of sudden death was a heart attack, and it was mostly men. Studies of sudden cardiac death and sexual activity from the US, France and South Korea show similar findings.Not just the older men.Researchers at the University of London found that this phenomenon is not limited to middle-aged men.The study looked at sudden cardiac death in cases referred to the center for cardiac pathology at St George's between January 1994 and August 2020.17 of these occurred within an hour of sexual activity. 35 percent of the cases occurred in women, which is higher than in previous studies, and the average age of death was 38 years.Older men have died from heart attacks. A sudden abnormal heart rhythm called sudden arrhythmic death syndrome orSADS was the cause of death in half of the cases.The second largest cause was anortic dissection. This is where the layers in the wall of the large artery from the heart give blood to the body and cause it to bulge and burst.Structural anomalies such as cardiomyopathy, a disease of the heart muscle that makes it harder for the heart to pump blood to the rest of your body, or a rare group of genetic conditions known as channelopathies were the reasons for the remaining cases.This is where the ion channels that let the two minerals in and out of the heart muscle don't work well. The electrical current through the heart muscle can be changed by the change in the cells.An altered heart rhythm can cause a lack of oxygen in the bloodstream and lead to a sudden cardiac arrest.A new study suggests that sudden cardiac death in people under the age of 50 is caused by sudden arrhythmic death syndrome or cardiomyopathies.Younger adults who have been diagnosed with these conditions should seek advice from their cardiologist on the risk associated with sexual activity.The low incidence of death in these studies suggests the risk is very low for people with existing heart conditions.The Senior Lecturer in Chemical Pathology is David C Gaze.This article is free to use under a Creative Commons license. The original article should be read.