Sleep duration and personality in Croatian twins

The relationship between NEO-five personality traits and sleep-related characteristics: A systematic review and meta-analysis

An increasing body of research has suggested personality traits as a possible predisposing factor for individual differences in sleep pattern and problems. However, the findings were mixed and there remained a lack of a quantitative synthesis. As searched in the four databases (Web of Science, Embase, PsycINFO, PubMed), 60 studies (n = 73,540; female = 60 %) that used standardized measures to evaluate the relationship between NEO-five personality traits and sleep-related outcomes (sleep quality and sleep duration) were identified. Meta-analyses were performed using random-effects model and the results suggested that poor sleep quality was associated with a higher level of neuroticism (r = 0.287) but a lower degree of openness (r = -0.042), conscientiousness (r = -0.132), extraversion (r = -0.086), and agreeableness (r = -0.064). Shorter sleep duration was found to be associated with a higher level of neuroticism (r = 0.066) but not with other personality dimensions. The findings were mainly limited to the general population. Future research should investigate whether comparable patterns of associations are present in the clinical populations. There is also a need for more research with a prospective design utilizing objective sleep measurements and to explore the mechanisms underlying the association of personality factors with sleep-related characteristics, especially sleep quality and duration.

The role of the DSM-5 maladaptive personality traits in adherence to sleep hygiene behaviors and sleep duration

Recent research explores the associations between maladaptive personality constructs proposed by the DSM-5 Alternative Model of Personality Disorders (AMPD) and general psychopathology whereas research on sleep hygiene behaviors and sleep duration is poor. This study first aimed to classify an adult population based on bedtime, mobile phone use before bedtime, and sleep duration. The second aim was to compare the AMPD trait domains including negative affectivity, detachment, antagonism, disinhibition, and psychoticism across the derived clusters. The cross-sectional study consisted of 481 college students from the west of Iran (mean age of 27.7 ± 6.8 years; 69.4% female). Several single items plus the Brief Form of Personality Inventory for DSM-5 were used for data collection. A hierarchical cluster analysis was performed to determine latent categories, and the AMPD domain scores between the clusters were compared using multivariate analysis of variance and post hoc tests. The cluster analysis identified three categories containing a vulnerable group (poor sleep hygiene behaviors but sufficient sleep duration), an unhealthy group (poor sleep hygiene behaviors plus insufficient sleep duration), and a healthy group (good sleep hygiene behaviors plus sufficient sleep duration). The results showed that the clusters significantly differed in all trait domains (except for detachment) and the total average score with higher mean scores, especially for the unhealthy cluster. Our findings highlight the meaningful impact of maladaptive personality traits on unhealthy sleep hygiene behaviors and insufficient sleep. Preventive medicine can identify at-risk populations by screening for maladaptive personality in early adulthood.

Effect of cognitive behavioral therapy for insomnia on sleep quality among college students: the role of hyperarousal and dysfunctional beliefs

BACKGROUND

Although cognitive-behavioral therapy for insomnia (CBT-I) is an effective treatment for sleep disorders, little is known about the role of hyperarousal (especially trait arousal) in CBT-I interventions. Therefore, this study investigated the role of trait arousal in the maintenance of sleep problems using cross-sectional and longitudinal methods.

METHODS

Study 1, 1209 Chinese university students (63.9% female) completed the Dysfunctional Beliefs and Attitudes about Sleep (DBAS-16), Pre-sleep Arousal Scale (PSAS), Arousal Predisposition Scale (APS), and Pittsburgh Sleep Quality Index (PSQI). The study calculated the moderating role of trait arousal in the relationship between dysfunctional beliefs about sleep and sleep quality. In study two, 89 participants completed the questionnaire used in Study 1 during pre-and post-treatment. A within-subjects mediation analysis examined the indirect effects of dysfunctional beliefs about sleep pre-sleep arousal (cognitive and somatic) on sleep quality. A within-subjects moderation analysis was used to investigate whether baseline trait arousal moderated sleep quality.

RESULTS

Cross-sectional findings indicated that pre-sleep cognitive arousal mediated the effects of dysfunctional beliefs about sleep on sleep quality and that trait arousal moderated the first half of the mediating pathway described above; longitudinal analyses indicated that changes in dysfunctional beliefs about sleep and pre-sleep cognitive arousal mediated changes in sleep quality, and that, in addition, trait arousal moderated changes in sleep quality.

CONCLUSION

Trait arousal correlates with the maintenance of sleep problems, and participants with higher trait arousal benefited less from CBT-I. Enhancement programs that incorporate mindfulness may be a direction for future research.

The moderating role of early-life parental adverse and positive factors in the genetic and environmental contributions to objectively assessed sleep duration in middle childhood

Early-life positive and adverse parental factors, such as positive parent personality and parental stress, affect the environmental context in which children develop and may influence individual differences in children's sleep health. This study examined the moderating role of early-life parental factors in the heritability (i.e., the extent to which individual differences are due to genetic influences) of objectively assessed childhood sleep duration. A total of 351 families from the Arizona Twin Project were studied. Primary caregivers (95% mothers) reported on multiple dimensions of stress and facets of their own personality when the twins were 12 months old. Seven years later (Mage = 8.43 years, SD = 0.68), families completed a home visit, and twins (51% female; 57% White, 29% Hispanic; 30% monozygotic, 39% same-sex dizygotic, 31% other-sex dizygotic) wore actigraph watches to assess their sleep, with caregivers completing similar assessments on their personality attributes and stress. Early-life positive parent personality moderated the heritability of sleep duration (Δ-2LL [-2 log likelihood] = 2.54, Δdf = 2, p = .28), such that as positive parent personality increased, the heritability of duration decreased. Early-life parental stress also moderated the genetic contribution to sleep duration (Δ-2LL = 2.02, Δdf = 2, p = .36), such that as stress increased, the heritability of duration increased. Concurrent positive parent personality and parental stress composites showed similar patterns of findings. Results highlight the likely contribution of parent positive traits and adverse experiences to the etiology of children's sleep health, with genetic influences on children's sleep more prominent in "riskier" environments. Understanding how genetics and environments work together to influence the etiology of sleep may inform prevention programs.

Behaviour genetics and sleep: A narrative review of the last decade of quantitative and molecular genetic research in humans

During the last decade quantitative and molecular genetic research on sleep has increased considerably. New behavioural genetics techniques have marked a new era for sleep research. This paper provides a summary of the most important findings from the last ten years, on the genetic and environmental influences on sleep and sleep disorders and their associations with health-related variables (including anxiety and depression) in humans. In this review we present a brief summary of the main methods in behaviour genetic research (such as twin and genome-wide association studies). We then discuss key research findings on: genetic and environmental influences on normal sleep and sleep disorders, as well as on the association between sleep and health variables (highlighting a substantial role for genes in individual differences in sleep and their associations with other variables). We end by discussing future lines of enquiry and drawing conclusions, including those focused on problems and misconceptions associated with research of this type. In this last decade our knowledge about genetic and environmental influences on sleep and its disorders has expanded. Both, twin and genome-wide association studies show that sleep and sleep disorders are substantially influenced by genetic factors and for the very first time multiple specific genetic variants have been associated with sleep traits and disorders.

Short sleep duration and adolescent health: does weekend catch-up sleep work and for whom?

OBJECTIVES

Despite evidence that sleep duration affects adolescent health, there remain important research gaps in the literature. Little is known about (1) whether the association between weekday sleep duration and health is confounded by unobserved individual heterogeneity and (2) the extent to which weekend catch-up sleep (WCS) duration moderates this association. This study addresses these gaps.

STUDY DESIGN

Using six waves of longitudinal data from the 2011-2016 Korean Children and Youth Panel Survey (N = 6633), this study examined the relationship between weekday sleep duration, WCS duration, and two measures of adolescent health, body mass index (BMI) and self-rated health (SRH).

METHODS

We estimated fixed effects models to account for individual-level heterogeneity.

RESULTS

Fixed effects estimates suggest that part of the associations between short sleep duration and adolescent health are confounded by unobserved individual heterogeneity (62% for BMI and 30% for poor SRH), although the associations remain statistically significant. Sleeping less than 6 h increased BMI by 0.203 and the probability of reporting poor SRH by about 2 percentage points. Controlling for individual heterogeneity, however, changed the sign of the WCS duration coefficient, suggesting that a longer WCS duration is positively associated with BMI (b = 0.021). No such patterns were found for SRH.

CONCLUSIONS

Short weekday sleep duration threatens adolescent health. WCS duration is protective only for those who are most sleep deprived.

The Relationship between Personality Traits and COVID-19 Anxiety: A Mediating Model

The COVID-19 pandemic has created a lot of fear and anxiety globally. The current study attempted to investigate the association among the big five personality traits and the two factors of COVID-19 pandemic anxiety (fear and somatic concern). Further, sleep quality as a mediator between personality traits and pandemic anxiety was also assessed. The study involved a cross-sectional sample of 296 adult Indians who were administered the 10-item short version of BFI along with the COVID-19 Pandemic Anxiety Scale and Sleep Quality Scale. Path analysis was used to test the theoretical model that we proposed. The overall model has explained 6% and 36% of the variance, respectively, for the factors of fear and somatic concern of COVID-19 pandemic anxiety. The path analysis model indicated that only the trait of neuroticism showed a significant direct and indirect effect on pandemic anxiety in the sample. Those scoring high on neuroticism indicated high levels of fear as well as somatic concern. Neuroticism also showed partial mediation through sleep quality on the factor of somatic concern. Agreeableness was the only other personality trait that indicated a significantly negative relationship with the factor of somatic concern. These relationships were independent of age, gender, and occupational status. These findings provide a preliminary insight into the slightly different relationship which has emerged between personality and COVID-19 pandemic anxiety in comparison to general anxiety.

Genetic and environmental influences on sleep-wake behaviors in adolescence

Study Objectives

To investigate the influence of genetic and environmental factors on sleep-wake behaviors across adolescence.

Methods

Four hundred and ninety-five participants (aged 9-17; 55% females), including 93 monozygotic and 117 dizygotic twin pairs, and 75 unmatched twins, wore an accelerometry device and completed a sleep diary for 2 weeks.

Results

Individual differences in sleep onset, wake time, and sleep midpoint were influenced by both additive genetic (44%-50% of total variance) and shared environmental (31%-42%) factors, with a predominant genetic influence for sleep duration (62%) and restorative sleep (43%). When stratified into younger (aged 9-14) and older (aged 16-17) subsamples, genetic sources were more prominent in older adolescents. The moderate correlation between sleep duration and midpoint (rP = -.43, rG = .54) was attributable to a common genetic source. Sleep-wake behaviors on school and nonschool nights were correlated (rP = .44-.72) and influenced by the same genetic and unique environmental factors. Genetic sources specific to night-type were also identified, for all behaviors except restorative sleep.

Conclusions

There were strong genetic influences on sleep-wake phenotypes, particularly on sleep timing, in adolescence. Moreover, there may be common genetic influences underlying both sleep and circadian rhythms. The differences in sleep-wake behaviors on school and nonschool nights could be attributable to genetic factors involved in reactivity to environmental context.

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.

Short-Term Memory Deficits in the SLEEP Inbred Panel

Although sleep is heritable and conserved across species, sleep duration varies from individual to individual. A shared genetic architecture between sleep duration and other evolutionarily important traits could explain this variability. Learning and memory are critical traits sharing a genetic architecture with sleep. We wanted to know whether learning and memory would be altered in extreme long or short sleepers. We therefore assessed the short-term learning and memory ability of flies from the Sleep Inbred Panel (SIP), a collection of 39 extreme long- and short-sleeping inbred lines of Drosophila. Neither long nor short sleepers had appreciable learning, in contrast to a moderate-sleeping control. We also examined the response of long and short sleepers to enriched social conditions, a paradigm previously shown to induce morphological changes in the brain. While moderate-sleeping control flies had increased daytime sleep and quantifiable increases in brain structures under enriched social conditions, flies of the Sleep Inbred Panel did not display these changes. The SIP thus emerges as an important model for the relationship between sleep and learning and memory.

Sleep: population epidemiology and concordance in Australian children aged 11-12 years and their parents

OBJECTIVES

To describe objectively measured sleep characteristics in children aged 11-12 years and in parents and to examine intergenerational concordance of sleep characteristics.

DESIGN

Population-based cross-sectional study (the Child Health CheckPoint), nested within the Longitudinal Study of Australian Children.

SETTING

Data were collected between February 2015 and March 2016 across assessment centres in Australian major cities and selected regional towns.

PARTICIPANTS

Of the participating CheckPoint families (n=1874), sleep data were available for 1261 children (mean age 12 years, 50% girls), 1358 parents (mean age 43.8 years; 88% mothers) and 1077 biological parent-child pairs. Survey weights were applied and statistical methods accounted for the complex sample design, stratification and clustering within postcodes.

OUTCOME MEASURES

Parents and children were asked to wear a GENEActive wrist-worn accelerometer for 8 days to collect objective sleep data. Primary outcomes were average sleep duration, onset, offset, day-to-day variability and efficiency. All sleep characteristics were weighted 5:2 to account for weekdays versus weekends. Biological parent-child concordance was quantified using Pearson's correlation coefficients in unadjusted models and regression coefficients in adjusted models.

RESULTS

The mean sleep duration of parents and children was 501 min (SD 56) and 565 min (SD 44), respectively; the mean sleep onset was 22:42 and 22:02, the mean sleep offset was 07:07 and 07:27, efficiency was 85.4% and 84.1%, and day-to-day variability was 9.9% and 7.4%, respectively. Parent-child correlation for sleep duration was 0.22 (95% CI 0.10 to 0.28), sleep onset was 0.42 (0.19 to 0.46), sleep offset was 0.58 (0.49 to 0.64), day-to-day variability was 0.25 (0.09 to 0.34) and sleep efficiency was 0.23 (0.10 to 0.27).

CONCLUSIONS

These normative values for objective sleep characteristics suggest that, while most parents and children show adequate sleep duration, poor-quality (low efficiency) sleep is common. Parent-child concordance was strongest for sleep onset/offset, most likely reflecting shared environments, and modest for duration, variability and efficiency.

Selection for long and short sleep duration in Drosophila melanogaster reveals the complex genetic network underlying natural variation in sleep

Why do some individuals need more sleep than others? Forward mutagenesis screens in flies using engineered mutations have established a clear genetic component to sleep duration, revealing mutants that convey very long or short sleep. Whether such extreme long or short sleep could exist in natural populations was unknown. We applied artificial selection for high and low night sleep duration to an outbred population of Drosophila melanogaster for 13 generations. At the end of the selection procedure, night sleep duration diverged by 9.97 hours in the long and short sleeper populations, and 24-hour sleep was reduced to 3.3 hours in the short sleepers. Neither long nor short sleeper lifespan differed appreciably from controls, suggesting little physiological consequences to being an extreme long or short sleeper. Whole genome sequence data from seven generations of selection revealed several hundred thousand changes in allele frequencies at polymorphic loci across the genome. Combining the data from long and short sleeper populations across generations in a logistic regression implicated 126 polymorphisms in 80 candidate genes, and we confirmed three of these genes and a larger genomic region with mutant and chromosomal deficiency tests, respectively. Many of these genes could be connected in a single network based on previously known physical and genetic interactions. Candidate genes have known roles in several classic, highly conserved developmental and signaling pathways—EGFR, Wnt, Hippo, and MAPK. The involvement of highly pleiotropic pathway genes suggests that sleep duration in natural populations can be influenced by a wide variety of biological processes, which may be why the purpose of sleep has been so elusive.

One of the biggest mysteries in biology is the need to sleep. Sleep duration has an underlying genetic basis, suggesting that very long and short sleep times could be bred for experimentally. How far can sleep duration be driven up or down? Here we achieved extremely long and short night sleep duration by subjecting a wild-derived population of Drosophila melanogaster to an experimental breeding program. At the end of the breeding program, long sleepers averaged 9.97 hours more nightly sleep than short sleepers. We analyzed whole-genome sequences from seven generations of the experimental breeding to identify allele frequencies that diverged between long and short sleepers, and verified genes and genomic regions with mutation and deficiency testing. These alleles map to classic developmental and signaling pathways, implicating many diverse processes that potentially affect sleep duration.

Central and Eastern European special issue

From November 16–19, 2014, twin researchers of the world will descend on the lovely city of Budapest, Hungary for the 3rd World Congress on Twin Pregnancy, held in conjunction with the 15th Congress of the International Society of Twin Studies (ISTS). It is the first time a Central and Eastern European country will host the congress. On this occasion, we were honored by the request from the editor of Twin Research and Human Genetics, Nick Martin, to put together a special issue highlighting twin research conducted in Central and Eastern Europe (CEE).