Night leg cramps typically affect the calves, although the feet and thighs may be plagued with the sudden and severe pain brought on by the cramps. The Mayo Clinic reports that most of the time, night legs cramps happen for no reason and pass as quickly as they came. The causes of severe leg cramps at night also may be a side effect of a more serious condition.
Age
Severe leg cramps at night are more prevalent in the elderly. Blood circulation slows down and the heart cannot pump enough blood to keep the peripheral muscles lubricated, resulting in leg cramps. Sleep is often disturbed by the painful cramps and older people often have difficulty moving to relieve the pain. Light massage that can ease the cramping becomes less of an option. Blood pressure medication, often a part of an aging person's regimen, also can cause leg cramps. Inactivity and lack of exercise contribute to the tight muscle contractions.
Disease
There are a number of diseases that list night cramps as a symptom or side effect. The Mayo Clinic reports that Addison's disease, type 2 diabetes, Parkinson's disease and peripheral artery disease can create the severe pain that occurs while sleeping. Alcoholism causes legs to cramp in the night, especially when the alcoholic has cirrhosis of the liver, a common ailment found in those who abuse alcohol. Night leg cramps could be a symptom of low electrolytes, dehydration or hypothyroidism.
Poor Ergonomics
Nocturnal night cramps, also referred to as a charley horse, can occur in people who work and stand on concrete floors all day, reports the Cleveland Clinic. Sitting for long periods of time can cramp the muscles, which react once they are straightened out and lying at rest at night. Sitting improperly on chairs that are too high and cut off the circulation to the lower legs has been known to result in leg cramps at night. Chairs that are not ergonomically tailored to an individual's proper sitting form also can create spinal compressions that end up causing leg cramps.
