Basketball players could be at heightened risk for dangerous blood clots that travel to the lungs, according to a small Spanish study. But the results — calculated from only six cases of so-called pulmonary embolism in US and European players — need to be replicated in larger studies, the authors caution.

The study follows recent PE cases suffered by high-profile NBA players Chris Bosh and Mirza Teletovic, who were forced to miss large portions of the 2014-15 NBA season.

“We have shown there is limited evidence of higher risk, so more research is needed,” said lead author Marti Casals of the national Research Center Network for Epidemiology and Public Health and the Public Health Agency of Barcelona. “However, our research should serve to warn the basketball community about the possible risk.”

“Professional athletes are exposed to high levels of effort which may result in a process of chronic inflammation, to repeated injuries, frequent air travel (economy-class syndrome) and the subsequent immobility, to novel treatments of injuries such as platelet-rich plasma and a whole series of additional circumstances that when combined may point out professional basketball as a special population at risk,” Casals told Reuters Health by email.