The diaphragm muscle, which is located underneath the lungs, usually drops down during inhalation to allow the lungs to expand. It then contracts or pushes upwards when exhaling, to push the air out. However, if the diaphragm becomes irritated, it may contract involuntarily, which in tuns pulls in air too quickly. As air rushes in, the vocal cords abruptly close, causing a hiccup. While this usually only lasts a few seconds, for some it can last for weeks or months or even occur while sleeping. If this happens, it is important to find the cause if possible, because over time it can lead to daytime fatigue and exhaustion.
Certain diseases can cause hiccups that are chronic or occur while sleeping. These include any condition that affects the nerves that control the diaphragm muscle, claims the Mayo Clinic. Tumors, goiters or other growths in the neck, laryngitis, pleurisy, pneumonia, stroke, gastrointestinal reflux disease, multiple sclerosis and brain injuries are common conditions that can cause hiccups during the day and at night. However, in many cases the cause of hiccups remains unknown.
While much more research is needed to understand the mechanisms involved, it may be that the oxygen deprivation that occurs with sleep apnea can trigger hiccups. Sleep apnea is a condition where the throat becomes temporarily blocked, or the brain fails to signal the respiratory muscles during sleep. This leads to frequent periods during the night where breathing stops temporarily. The person often awakes with a loud snore or gasp. This abnormal breathing pattern may trigger hiccups, states the Journal of Applied Physiology. In these cases, hiccups that occur at night also tend to make blood pressure either drop or rise.
Chronic diseases that affect metabolism can also cause hiccups that become chronic and may occur during sleep. These include kidney disease, diabetes and electrolyte imbalances. Eating large meals and drinking alcohol can exacerbate this symptom, warns the OhioHealth Central Ohio and Columbus Hospitals website. In addition, certain drugs that suppress the nervous system may contribute to hiccups at night. This includes tranquilizers, barbiturates and steroids.