It's not the hair, Rob, it's the haunted gaze. The man is 60, not 80. And that is how he looked four years ago:
Obviously, the healthy life on a New Zealand farm and eating and sleeping right don't age you quite as much. And the luxury accorded to him when he is touring with one of the world's biggest bands doesn't explain that physical deterioration either. Meth does, though there can be other reasons of course, but the difference is more than a "bad day" or an unfavorable picture can explain.