The influence of age and sex on sleep latency in the MSLT-30 -: A normative study

Study Objectives: The Multiple Sleep Latency Test-30 (MSLT-30) is a variation of the Multiple Sleep Latency Test with a fixed duration of 30 minutes for each of 5 test sessions. It requires less effort for reliable recording and is not susceptible to on-line scoring errors. The aim of the study was to provide normative data for the clinical use of the MSLT-30 and to evaluate the influence of age, sex, and other sociodemographic variables. Design: An MSLT-30, along with measures of mood, objective, and subjective sleepiness was performed in a sample of healthy subjects in a balanced quota design. Setting: Sleep laboratory in a sleep disorders center. Participants: One hundred subjects with no complaint of sleep disturbance or daytime sleepiness, 10 men and 10 women each from 5 age decades from 20 to 69 years. Interventions: None. Results: Mean latency to sleep stage 1 or any other sleep stage was 13.9 +/- 6.9 minutes. The SL-30 showed a clear quadratic association with age, with the shortest latencies in the middle age groups. No correlation was found between the mean latency to sleep stage 1 or any other sleep stage and sociodemographic variables or other measures of daytime sleepiness (Epworth Sleepiness Scale, vigilance test), mood scales, sleep quality (Pittsburgh Sleep Quality Index), and amount of prior sleep. Conclusions: Sleep latencies in normal subjects are age dependent in a quadratic fashion, with a minimum in middle-aged subjects. This reconciles the findings of a long mean sleep latency in the MSLT of adolescents and of an increase on the mean sleep latency with age in adults.