How can I treat painful night leg cramps?

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Q. I occasionally get an excruciating leg cramp that wakes me from sleep. What causes leg cramps, and how can I prevent them?

A. Although nocturnal leg cramps can strike people at any time of life, they become more frequent with age. Among people older than age 50, about half report having leg cramps, a third say they are awakened at night by them, and 15% report having cramps about once per week.