He passed away at 53. He really aged due to heat and diabetes problems.
The real underlying cause of the diabetes and heart problems was Robinson's being overweight. I saw him play quite a number of times in his later years with the Dodgers and the extra poundage he was carrying was apparent. Too bad medical science hadn't evolved at that time to the point where losing extra poundage was one of the mainstays of treating Type 2 diabetes. One would think that a guy with Robinson's character would have complied with such medical advice if it was offered appropriately.