An elderly Catholic priest charged with indecently assaulting two boys more than 50 years ago has dementia and it would be "inappropriate" for him to stand trial, a court has heard.

Hugh Edward Murray, now 81, is charged with five counts of indecently assaulting the boys between 1966 and 1978.

In Sydney's Downing Centre District Court on Monday, Judge Greg Woods heard that Murray, a diabetic who had suffered more than 10 cardiac arrests, was not fit to stand trial on the charges, which he denies.

"He has got dementia, he has got a diagnosis of cognitive impairment," Dr John Albert Roberts said in giving evidence about Murray's health.

Dr Roberts said Murray had his sixth pacemaker fitted in 2006, following a string of heart attacks, and agreed Murray's cardiac history was "lengthy and complex".