I'm reasonably sure it depends on the sort of interrupt. This is based on introspection, so it's not very reliable, but an interrupt that involves thinking about something different-but-similar is murder, while e.g. switching tracks entirely to reading a book doesn't seem to be nearly as much of a problem.

Getting up to take a walk is something else again; it doesn't actually break my concentration at all, I'll still be thinking about the same problems while walking.