We all know about the blood issue. Every year, many witlesses will die because of not taking blood. The exact numbers vary, and are augmented because of the number of witlesses that are involved in accidents or persecution while out in field circus. But every one of those is one too many, especially when children are involved.
There are other ways that being a witless can kill, and some are not readily apparent. One can die in an accident on the way to field circus or a boasting session. Persecution, dog attacks, and falls also happen while out in field circus.
There is the Pioneer Diet. The lifestyle deprives one of sleep and stresses people into early death. And, a steady diet of fast, good tasting poison is a shortcut to an early grave. I have seen many of them get cancer or heart disease in their 40s through early 60s. Lack of proper exercise is also a problem for many, as is the pollution of excess driving (often in cities).
General persecution is another hazard. People in foreign lands get mobbed for being witlesses or for obeying their rules. What happened in Malawi is a prime example. Burundi also persecuted them en masse. People die from that. They also die for refusing to carry out orders from the government, often as simple as saluting the flag.
An obscure one, that could become more common, is the number of child abduction/murders that happen. What happens then is that a witless, often a single "brother", will be wrongly apprehended for a pedophile case. That will be brought to trial, and the "brother" will be found guilty or it will be a lengthy trial. In the meantime, the killer of that child (it was a killing, not a pedophile case) will kill another one. Had the witless not been a witless, they would have closed the lead and found the real killer before he had a chance to get another victim. With the pedophile embarrassments sure to follow last fall's NBC report, that could become more common.
We also have poverty and stagnation. People that are witlesses are being ordered to quit college or to not go. Full time workers are being asked to cut their hours and move to pioneer. This means the well to do witless is going to become rarer in the future. It also means people will not have the means to support themselves properly, and if medical care is critically needed, it will not be available (whether allopathic care for a crisis or natural care for ongoing conditions). This is especially true for those who move to South America or Africa to help where the cancer is fastest growing and conditions are more conducive to infections and complications from regular hazards. Lack of money and stimulation also means depression and more suicide and preventable diseases.
I am sure there are yet other ways that being a witless can kill one.