Genetic and Environmental Influences on Individual Differences in Sleep Duration During Adolescence

Heritability of sleep duration and quality: A systematic review and meta-analysis

Epidemiological and interventional research has highlighted sleep as a potentially modifiable risk factor associated with poor physical and mental health. Emerging evidence from (behavioral) genetic research also shows that sleep characteristics are under strong genetic control. With this study we aimed to meta-analyze the literature in this area to quantify the heritability of sleep duration and sleep quality in the general population. We conducted a systematic literature search in five online databases on January 24th 2020. Two authors independently screened 5644 abstracts, and 160 complete articles for the inclusion criteria of twin studies from the general population reporting heritability statistics on sleep duration and/or quality, and written in English. We ultimately included 23 papers (19 independent samples: 45,328 twins between 6 mo and 88 y) for sleep duration, and 13 papers (10 independent samples: 39,020 twins between 16 and 95 y) for sleep quality. Collectively, we showed that 46% of the variability in sleep duration and 44% of the variability in sleep quality is genetically determined. The remaining variation in the sleep characteristics can mostly be attributed to the unique environment the twins experience, although the shared environment seemed to play a role for the variability of childhood sleep duration. Meta-analyzed heritability estimates for sleep duration, however, varied substantially with age (17% infancy, 20-52% childhood, 69% adolescence and 42-45% adulthood) and reporter (8% parent-report, 38-52% self-report). Heritability estimates for actigraphic and Polysomnography (PSG)-estimated sleep were based on few small samples, warranting more research. Our findings highlight the importance of considering genetic influences when aiming to understand the underlying mechanisms contributing to the trajectories of sleep patterns across the lifespan.

Associations of sleep with psychological problems and well-being in adolescence: causality or common genetic predispositions?

BACKGROUND

Whereas short and problematic sleep are associated with psychological problems in adolescence, causality remains to be elucidated. This study therefore utilized the discordant monozygotic cotwin design and cross-lagged models to investigate how short and problematic sleep affect psychological functioning.

METHODS

Adolescent twins (N = 12,803, 13-20 years, 42% male) completed questionnaires on sleep and psychological functioning repeatedly over a two-year interval. Monozygotic twin pairs were classified as concordant or discordant for sleep duration and trouble sleeping. Resulting subgroups were compared regarding internalizing problems, externalizing problems, and subjective well-being.

RESULTS

Cross-sectional analyses indicated associations of worse psychological functioning with both short sleep and problematic sleep, and cross-lagged models indicate bidirectional associations. Longitudinal analyses showed that an increase in sleep problems experienced selectively by one individual of an identical twin pair was accompanied by an increase of 52% in internalizing problem scores and 25% in externalizing problem scores. These changes were significantly different from the within-subject changes in cotwins with unchanged sleep quality (respectively, 3% increase and 5% decrease). Psychological functioning did, however, not worsen with decreasing sleep duration.

CONCLUSIONS

The findings suggest that sleep quality, rather than sleep duration, should be the primary target for prevention and intervention, with possible effect on psychological functioning in adolescents.

Characteristics of sleep in socially vulnerable adolescents

IMPORTANCE

This study may help understand the effects of an unfavorable environment in sleep quality of adolescents.

OBJECTIVE

To investigate sleep quality in socially vulnerable adolescents, correlating the results with cognitive problems and attention deficit/hyperactivity disorder, and assessing the effectiveness of sleep hygiene and an educational intervention.

DESIGN

Cross-sectional and interventional study.

SETTING

an educational charitable center supported by a Catholic institution, in Porto Alegre, southern Brazil.

PARTICIPANTS

125 male and female high school students.

INTERVENTIONS

As first step the subjects were administered specific questionnaires, the Pittsburgh Sleep Quality Index (PSQI) and the Epworth Sleepiness Scale (ESS), followed by an educational activity that was combined with an unblinded, randomized interventional study. Next, a cross-sectional study was conducted to determine the influence of cognition and ADHD on the sleep.

MAIN OUTCOME AND MEASURES

Sleep was evaluated using PSQI and ESS. Cognitive assessment was based on the Wechsler Abbreviated Scale of Intelligence and ADHD by a clinical interview the Multimodal Treatment Study for ADHD (MTA-SNAP-IV).

RESULTS

The average duration of sleep per night were 6 h 30 m. 80% of the sample presented sleep complains. Of these, 44% had excessive daytime sleepiness and 69.6% had poor sleep quality related to use of electronic media, environmental violence, and emotional issues. There were no significant associations between sleep problems and cognitive problems or ADHD. Sleep quality improved in 17% of the 53 students with previous sleep complains who participated in any of the two interventions.

CONCLUSIONS

A high prevalence of sleep deprivation and sleep complains was found in the study sample. The interventions showed some positive effects on the improvement of sleep quality.

Linking emotional distress to unhealthy sleep duration: analysis of the 2009 National Health Interview Survey

OBJECTIVE

The objective of the study was to examine the independent association of emotional distress with unhealthy sleep duration (defined as <7 or >8 hours).

METHODS

Data from the 2009 National Health Interview Survey (NHIS), a cross-sectional household survey, were analyzed to investigate the associations of emotional distress with unhealthy sleep durations, adjusting for sociodemographic factors, health risks, and chronic diseases through hierarchical multiple logistic regression analysis.

PARTICIPANTS

A total of 27,731 participants (age range 18-85 years) from the NHIS 2009 dataset were interviewed.

MEASURES

Unhealthy sleep duration is defined as sleep duration <7 or >8 hours, whereas healthy sleep is defined as sleep duration lasting for 7-8 hours. Emotional distress is based on the Kessler 6 Non-Specific Distress Battery, which assesses the frequency of feeling sad, nervous, restless, hopeless, worthless, and burdened, over a 30-day period.

RESULTS

Of the sample, 51.7% were female; 83.1% were white and 16.9% were black. Eleven percent experienced emotional distress and 37.6% reported unhealthy sleep. Adjusted logistic regression analysis revealed that individuals with emotional distress had 55% greater odds of reporting unhealthy sleep (odds ratio [OR] =1.55, 95% confidence interval [CI] =1.42, 1.68, P<0.001).

CONCLUSION

Emotional distress, an important proxy for poor psychological health, was a significant predictor of unhealthy sleep, independent of the influences of several factors including demographic (age, education, sex, race/ethnicity, and family income), health risks (alcohol consumption and smoking status), and chronic diseases/conditions (diabetes, obesity, hypertension, heart disease, cancer, and arthritis).