BERLIN, May 24 (Xinhua) -- Sports doctors from Germany, Switzerland and the United States will study the impact of headballs on the health of footballers, the German Press Agency (DPA) reported on Thursday, citing a statement issued at the ongoing German Olympics Sports Physicians' Congress.

At an event held during the Congress in Hamburg which lasts from Thursday to Saturday, the head of the study, neurologist Claus Reinsberger, said it is not certain whether headballs harm the brain in the long run, although they do not lead to concussions necessarily.

The study is scheduled to run for three years and should be completed by 2020. Footballers of the U21 from Hamburger SV are involved, together with some Swiss players.

The scientists planned to examine the footballers with magnetic resonance tomograph and then observe all the headballs during training sessions and games. Finally, the players will be re-examined clinically.

Previous studies have suggested that communication between certain parts of the brain is disturbed as a result of headballs.

"It's clear that there are changes and adaptations of the brain," Reinsberger was quoted by the DPA as saying.

Around one thousand sports physicians, scientists, orthopedists, pediatricians, surgeons, neurologists, cardiologists, internists and therapists from 18 countries and regions will exchange their latest findings in Hamburg at the Congress.

The organizers of the Congress are the German Society for Sports Medicine and Prevention and the Society for Orthopedic Traumatological Sports Medicine.