Quality of sleep in patients with nocturnal leg cramps and validity of a single-item measure of cramp-related sleep disturbance: an observational study.

Only a few studies have addressed the impact of nocturnal leg cramps on sleep quality. We investigated the association between nocturnal leg cramps and sleep disturbance using the Pittsburgh Sleep Quality Index (PSQI), and assessed the criterion validity of a single-item daily measure of cramp-related sleep disturbance. In this prospective observational study conducted in Western Switzerland from January 2015 to June 2016, 20 primary care physicians recruited up to 20 consecutive patients aged >50 years. During a 2-week period, patients recorded on a daily basis the number of cramps and their level of sleep disturbance using a single item measure (10-point visual analogue scale from 0 to 10). They also completed the PSQI questionnaire on day 14. Patients were considered as “poor sleepers” if the PSQI score was >5/21. The criterion validity of the single-item measure (averaged over the 2-week period) was assessed using Spearman’s rank correlation coefficient to determine the correlation with the PSQI. 129 patients participated (women 67%, mean age 70 years). The single-item and the PSQI mean scores were 2.6/10 (standard deviation 2.5) and 6.1/21 (SD 3.9), respectively. Being a “poor sleeper” (47% of patients) was not statistically significantly associated with patients’ characteristics and number of cramps. The averaged single-item measure was not correlated with the PSQI score (Spearman’s rank correlation 0.08, p-value 0.51). In this primary care sample, poor sleep quality was not associated with suffering from a higher number of nocturnal cramps, and a single-item mean score was not a valid instrument to screen for sleep disturbance among these patients.