Multiple choice general knowledge Which is the non-contagious disease that is the most common in the world? DIABETES HYPERTENSION TOOTH DECAY HEART DISEASE Reveal answer Fill a bubble to check yourself C Correct answer Explanation Tooth decay (dental caries) is the most common non-contagious disease worldwide, affecting about 2.3 billion people globally according to WHO statistics. It's caused by bacteria in the mouth converting sugars into acids that dissolve tooth enamel.