MUNICH (Reuters) - Young men who die suddenly after being arrested by the police may be victims of a new syndrome similar to one that kills some wild animals when they are captured, Spanish researchers said on Tuesday.

A plainclothes detective with the Las Vegas Metropolitan Police Department handcuffs a man on the Las Vegas Strip, August 8, 2007. REUTERS/Steve Marcus

Manuel Martinez Selles of Madrid’s Hospital Gregorio Maranon reached the conclusion after investigating 60 cases of sudden unexplained deaths in Spain following police detention.

In one third of the cases, death occurred at the point of arrest, while in the remainder death was within 24 hours, Selles told the annual meeting of the European Society of Cardiology.

All but one of the casualties were male and their average age was just 33 years, with no previous history of cardiovascular disease.

“Something unusual is going on,” Sells said.

Just why they died remains a mystery but he believes young men, in particular, may experience surges in blood levels of chemicals known as catecholamines when under severe stress.

Adrenaline is one of the most abundant catecholamines.

“We know that when a wild animal is captured, sometimes the animal dies suddenly,” he said.

“Probably when these young males are captured it is very stressful and their level of catecholamines goes very high and that can finish their life by ventricular fibrillation (cardiac arrest).”

Selles compiled his study -- the first of its kind in any country -- by scouring Spanish newspapers for cases of unexplained death after police detention over the past 10 years.

Only sudden deaths with no clear causes were included and autopsy reports were checked to exclude the possibility of mistreatment or past serious medical conditions.

Twelve of the victims were drug users but Selles said this was not thought to have contributed to their deaths.

Jonathan Halperin of the Mount Sinai Medical Center in New York, who was not involved in the research, said the concept of a heart stress syndrome triggered by a flood of adrenaline or other chemicals was “a reasonable hypothesis”.

“We all know stress is bad for you and this may be stress in the extreme,” he said.