Young adults who report sleeping fewer hours per night on average than do their counterparts are at elevated risk for persistent or new-onset psychological distress, according to results of a large, prospective cohort study.
Researchers found a linear correlation – a 14% greater risk for higher psychological distress for each hour slept fewer than 8, on average, per night – after they controlled for possible confounders. Sleeping 8-9 hours per night is recommended.
A total of 19,648 Australians (aged 17-24 years) reported their sleep hours for the previous month in a survey of registered drivers. Researchers found almost one-third (32.5%) had high baseline levels of psychological distress (defined as a score greater than 21 on the K10 (Kessler Psychological Distress Scale), a 10-item instrument that screens for feeling “tired out for no reason,” nervous, hopeless, restless, or depressed during the previous 4 weeks.
Psychological distress was most acute among the less than 2% of young adults who reported sleeping an average 5 hours or fewer per night, representing a group that might benefit the most from an intervention to improve their sleep routine. Another 18% reported sleeping an average 7 hours or fewer per night, and 30% reported sleeping 7-8 hours each night.
The full findings of the study were published in the September issue of the journal Sleep (2010;33:1139-45).
Lead researcher Dr. Nicholas Glozier and his associates also resurveyed a random sample of 2,937 respondents 12-18 months later. They found that high levels of distress persisted for 32% of the 945 who were initially distressed at baseline. In addition, 12% of those with no initial elevated distress (239 of 1992 respondents) had new-onset distress 1 year later, reported Dr. Glozier, who is on the psychological medicine faculty at the Brain and Mind Research Institute at the University of Sydney.
Again, a linear association was found between shorter sleep duration and likelihood for onset of psychological distress (relative risk, 1.12). Risk was most pronounced among those reporting an average 5 hours or fewer of sleep (RR, 3.25), compared with other participants.
This is the first prospective study to link shorter sleep duration in young adults with increased psychological distress, the researchers noted. Interestingly, there was no increased risk of psychological distress at any time in the study among those who reported sleeping an average 9 hours or more per night.
Based on these findings, clinicians could potentially identify young adults who are at elevated risk for persistent or new onset psychological distress by asking about sleep duration. Also, because young adulthood is a time when elevated psychological distress could develop into depression and many other psychiatric conditions, short sleep duration could be an important marker for early intervention, the authors wrote.
The authors acknowledged the difficulty associated with any populationwide effort to improve sleep (such as reducing late-night television viewing, computer gaming, and Internet use). Instead, they recommend that clinicians identify and focus their efforts on young adults who are at highest risk: those who report current distress or extremely short sleep duration. Other researchers demonstrated an association between short sleep duration and later bedtimes with depressed mood and suicidal ideation among adolescents (Sleep 2010;33:97-106).
Disclosures: There was no industry support for the study. Dr. Glozier is a member of the Sanofi-Aventis advisory board and is a speaker for CSL Laboratories. Dr. Ian Hickie, one of the investigators, formerly served as chief executive officer and clinical adviser for Beyondblue, the Australian National Depression Initiative, and has led projects supported by numerous drug industry partners. The other authors reported no relevant disclosures.