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 26 years 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 selfreported
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.