Of course BJJ is not safe. It is a martial art. The word "martial" means "warlike." It involves holds and throws and joint locks and potentially choking people out. Does any of that sound remotely safe? You can get hurt from it. You can die from it. Of course, you can die from a stroke while watching TV. In fact, that is one of the most common things that people are doing when they suffer a stroke. You don't practice BJJ because it is safe. You practice BJJ because you come to the conclusion that the risk is reasonable compared to the reward. Given how many people practice BJJ and how few of them die, you are probably going to be just fine. Then again, you might not.