Any anemia, if not treated, will only get worse over time, including iron-deficiency anemia. Prolonged anemia can impact various organ systems throughout the body. In the nervous system, it can cause headaches, dizziness, insomnia, frequent dreams, and memory decline. In children, iron-deficiency anemia can even affect intellectual development. In the respiratory system, it can lead to deeper and faster breathing, and increase the risk of respiratory infections. In the circulatory system, it can manifest as low blood volume, and long-term severe anemia can lead to anemic heart disease, causing arrhythmias and heart failure. In the digestive system, it can manifest as reduced appetite, and in severe cases, it can cause constipation, diarrhea, etc.