Biological and psychological correlates of self-reported and objective sleep measures.

OBJECTIVE Objective and self-reported sleep are only moderately correlated and it is uncertain if these two types of sleep measures are associated with distinct biological and psychological outcomes. METHODS Participants were 119 healthy women aged 26years on average. Cortisol and blood pressure assessed over one day were the measures of biological function. Psychological variables included optimism, life satisfaction, positive and negative affect as well as emotional distress. Sleep was assessed with the Pittsburgh Quality Index (PSQI), wrist actigraphy and sleep diaries. RESULTS Global sleep ratings on the PSQI were unrelated to objective sleep efficiency, duration or latency. Sleep duration derived from sleep diaries was highly correlated with objective duration but was unrelated to the PSQI measure. More disturbed sleep on the PSQI was associated with lower psychological wellbeing, as indicated by reduced levels of optimism, life satisfaction and positive affect as well as greater negative affect and emotional distress. Objective sleep efficiency was reduced among participants with lower positive and higher negative affect but there were no other associations between objective sleep indicators and psychological variables tested in our study. Participants with poorer self-reported sleep had lower cortisol awakening response while those with longer objective sleep latency had higher diastolic blood pressure, independently of covariates. CONCLUSION Our study reveals that self-reported and objective sleep measures, in particular those regarding sleep quality, are weakly associated but have different psychological and biological correlates. This suggests that findings relating self-reported sleep may not necessarily be corroborated by objective sleep indicators.