Maternal postpartum sleepiness and fatigue: associations with objectively measured sleep variables.

OBJECTIVE To explore whether standardized survey instruments and objective performance measures differentiate traditional constructs of sleepiness and fatigue among a sample of postpartum mothers. Additionally, we wanted to explore the independent associations among these measures with actigraphically measured nocturnal sleep variables. METHOD Seventy-nine postpartum mothers' subjective sleepiness, fatigue, and performance measures [Stanford Sleepiness Scale (SSS), Epworth Sleepiness Scale (ESS), Visual Analogue of Fatigue Scale (VAS), Profile of Mood States (POMS) subscale items, and the Psychomotor Vigilance Test (PVT)] and objective actigraphically measured sleep were collected during postpartum week 11. A principal components analysis was calculated, then regressions were calculated among resulting factors and among individual measures with total sleep time and sleep efficiency. RESULTS Three factors accounted for 83.84% of model variance. Factor 1 (41.41%) included the SSS, ESS, and the VAS. Factor 2 (28.13%) included only PVT variables. Factor 3 (14.30%) included the two POMS subscale items. Factor 1 was associated with nocturnal sleep time and Factor 2 was associated with sleep efficiency. The ESS was independently associated with nocturnal sleep time, whereas, POMS-Vigor subscale and median reaction time, together, were associated with sleep efficiency. CONCLUSION Among postpartum mothers, standard instruments used to measure sleepiness, fatigue, and performance were distributed among three distinct factors that did not clearly identify traditional sleepiness and fatigue constructs. Objectively measured sleep time and sleep efficiency were associated with specific factors, as well as specific measures, that correspond to sleepiness and fatigue states.