Epidemiology

Idiopathic leg cramps are common. Estimates of prevalence and frequency of attacks vary, but most adults report having experienced leg cramps at some time.[3][8][9][10][11] Prevalence and frequency of attacks are higher in older people.[9][11]​​[12][13]​​ Women are reported to experience cramps more frequently than men.[10][11]​​[14]​​

Idiopathic cramps are less common in children than in adults. Nocturnal leg cramps were reported in about 7% of a cohort of around 2500 healthy children, beginning only after aged 8 years, and peaking in prevalence at aged 16 to 18 years.[15] Most affected children have infrequent cramps.[15]

The mean duration per cramp episode has been reported to be 8 to 9 minutes in adults, and 2 minutes in children.[9][10][15] About 75% of cramp episodes in adults and children occur at night.​[9][10][15]​​

Idiopathic cramps usually involve single muscles or part of a muscle, particularly the gastrocnemius.[1][16]​​ Most episodes involve the calf muscles, followed by the foot muscles; foot cramps have been reported to be more common in women than in men.[3][9][14] Local cramps in other muscles are less common. However, they are frequently noted in the context of neuromuscular disease.[1]

Muscle cramps are commonly experienced by pregnant women, particularly during the last trimester.[17] These significantly remit after parturition.[17]

Estimates of the prevalence of cramps during haemodialysis range from 15% to 87%.[18][19][20][21][22] The risk of cramps may be similar during haemodialysis and peritoneal dialysis.[20]

Estimates of the prevalence of cramps in patients with cirrhosis range from 22% to 88%.[23][24][25][26][27] Clinically relevant cramps (defined as cramps occurring at least once weekly, negatively affecting the patient's quality of life, and requiring analgaesia) were reported in 12% to 42% of these patients.[23] Cramp prevalence is significantly higher in patients with cirrhosis than in controls or in patients with chronic non-cirrhotic liver disease. In contrast to other populations, patients with cirrhosis more frequently exhibit cramping during rest rather than during sleep, and higher proportions of episodes involve the fingers and thighs.[24][25]

A number of other chronic medical conditions are associated with nocturnal leg cramps. These include depression, arthritis, cardiovascular disease, and respiratory disease.[11] 

People taking strenuous exercise, particularly in endurance events such as triathlons, marathons, and ultramarathons, are predisposed to exercise-associated muscle cramps (EAMC).[28][29][30] People participating in team sports (e.g., rugby) also report high levels of EAMC.[28][30]

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