Research into the brains of 11 former footballers and rugby players who had dementia has found evidence of brain injury in the majority of cases.
Dementia has been linked to chronic traumatic encephalopathy (CTE) which is caused by repeated blows to the head, with some believing heading a football can be a contributing factor.
However, researchers at Glasgow University said that while CTE was prevalent in a high number of the patients studied, in many cases it was not the “primary pathology driving the dementia”.
The study published in the journal Acta Neuropathologica said that while CTE might be common in former athletes with dementia, its clinical significance remains uncertain.
Dr Willie Stewart, of the university’s Institute of Neuroscience and Psychology, said: “Our findings suggest that while CTE is prevalent in a high number of the patients we studied, in many cases it is not the primary pathology driving the dementia.
“In other words, while head injury-associated degenerative brain disease is important in these patients, the reality of dementia in former footballers and rugby players is that the disease is more than just CTE, and more complex.”
Former England captain Alan Shearer, who has campaigned for research into this issue, said: “This is incredibly important work by Dr Stewart and his team in Glasgow. Finally, we are beginning to see some progress towards understanding dementia in former footballers and I look forward to hearing more from these studies.”
Following the deaths of Lisbon Lions Billy McNeill and Stevie Chalmers in April, former Celtic teammate Jim Craig called for tests into a possible link between heading a football and dementia.
Research in the United States has previously found evidence of CTE in the brains of former American footballers. The Glasgow research was funded by the Football Association (FA) and Professional Footballers Association; the US National Institute of Neurological Disorders and Stroke and NHS Research Scotland.