Arithmophobia–is that a fear of arithmetic? As you probably already know, there are people who have irrational fear of certain numbers. It’s called “arithmophobia” or “numerophobia.” As it turns out, this is true of different cultures as well.
Since there isn’t any actual reason to be afraid, different cultures wind up being afraid of different numbers. In Mandarin, Cantonese and Japanese, for example, the word for the number four just happens to sound like the word for “death.” That’s enough to start a superstition going; many people who speak these languages are afraid of the number four. Although there’s nothing dangerous about the number four, the fear of four can be dangerous indeed.
A study reported in the British Medical Journal looked at mortality statistics in the United States over twenty-five years. The study found that Chinese and Japanese people were thirteen percent more likely to die of heart failure on the fourth day of any given month than other folks.
This pattern was not seen in deaths due to any other causes. Since cardiac arrest is linked to stress, if you are going to die of a heart attack, then being afraid of day four may make it more likely that you will actually have a heart attack on that day.