Nocturnal leg pain or cramps are sudden tightening in the calf muscles that wake people up. Occasionally the foot gets cramps. The condition becomes more common as people age: over seventy percent of Americans over age fifty have occasional nocturnal leg cramps. But people of any age can have nocturnal leg cramps, and pregnant women (third trimester) are particularly susceptible.
This sleep-wake disorder is a frequent cause of sleep disturbance. Nocturnal leg cramps may delay sleep onset, wake the sleeper up, and delay the patient’s ability to fall back asleep, all of which results in lower sleep efficiency.
Scientific studies have shown increased muscle activity in the affected leg right before the cramp happens. In most cases, it is “idiopathic” - there is no obvious physiological cause. Sometimes the cramps can be attributed to medications or a structural problem in the body such as lumbar spinal canal stenosis or metabolic diseases (e.g. hypoglycemia or hypothyroidism). Diuretic pills, which flush minerals out of the body, can also be a risk factor.
A diet rich in potassium-containing foods can prevent cramps as can muscle-stretching, exercise, and drinking water. Dehydration is a risk factor for cramps, as endurance athletes know. Magnesium pills sometimes relieve leg cramps for pregnant women.
Quinine sulfate reduces the number of nocturnal leg cramps, but not severity or duration. The benefit of quinine appears to be cumulative, and patients take it regularly – not just when they are having cramps. This treatment is not used in the US much any more. The FDA withdrew approval in 2006. There are other drugs, but most doctors recommend exercise and proper nutrition and living with the cramps.