Parents’ assessment of circadian preference in elementary school-aged children: Validity and relations to educational outcomes

Circadian preference and intelligence - an updated meta-analysis

A large number of previous studies reported a link between circadian preference and psychometric intelligence with mixed results and various hypotheses about the source of this correlation. In this study, we aimed to update a previous meta-analysis about the correlation between circadian preference and intelligence. Our literature search identified a large number of new studies, resulting in an increase of over 100% in the number of studies and over 400% in the number of involved participants (total k = 30, total N = 11160) over the previous meta-analysis, sampling a much wider age range from children to adults in late middle age. Our meta-analysis revealed no significant link between morningness and intelligence (r = -0.008) when the entire sample was studied, and no evidence for publication bias. This overall effect, however, obscured the moderating effect of age. The morningness-intelligence correlation decreased with mean sample age (R² = 54%), ranging from a non-significant positive trend in children and adolescents to a significant negative correlation after young adulthood. Eveningness was positively correlated with intelligence (r = 0.056), but this finding is based on a more age-restricted sample and only reached significance with some model specifications. We hypothesize that the age-moderated correlation between circadian preference and intelligence reflects social effects, where more intelligent individuals are more able to adjust their daily schedules to their natural circadian rhythm.

Circadian preference and academic achievement in school-aged students: a systematic review and a longitudinal investigation of reciprocal relations

We provide a systematic review of findings on the relation between circadian preference and school achievement published after the last comprehensive review in 2015. We further test this relation in a longitudinal study. Our review of 26 studies revealed a positive relation between morningness and students' school achievement, and a negative relation between eveningness and school achievement. In most studies, these relations were not affected by students' age, sex, or intelligence, but were significantly mediated by students' conscientiousness, motivation, and sleep behavior. Furthermore, circadian preference and school achievement showed no significant relation when school started in the afternoon. All studies were cross-sectional. Therefore, the direction of the relations between circadian preference, school achievement, and potential mediating variables like conscientiousness and motivation could not be investigated. In our longitudinal study, we tested the direction of the relations between circadian preference, academic achievement, conscientiousness, self-efficacy, and attitude toward school over time in a sample of 764 German high school students who were tested in the first (T1) and third (T2) year of high school. Findings from confirmatory cross-lagged models indicated reciprocal relations between circadian preference and school achievement: T1 morningness positively predicted change in grade point average over time while T1 grade point average positively predicted change in morningness and negatively predicted change in eveningness. Furthermore, T1 conscientiousness and T1 attitude toward school both positively predicted change in morningness, whereas T1 morningness and T1 eveningness did not significantly predict change in these variables.

Sleep habits and circadian preferences in school-aged children attending a Mexican double-shift school system

OBJECTIVE

To determine the differences between sleep habits and circadian preference in school-aged children attending a Mexican double-shift school system.

METHODS

This cross-sectional study consisted of 400 elementary public-school children (mean age = 10.77, SD = 0.70 y, from fourth, fifth and sixth grades) in Reynosa, Tamaulipas, in northeastern Mexico. Attending a double-shift school system: 200 from the morning shift and 200 in the afternoon shift. Specific questions regarding sleep habits were collected and for circadian preference, the Morningness-Eveningness Scale for Children (MESC) was used.

RESULTS

Multivariate analysis reported no sex differences. Children attending at the morning shift during weekdays rose earlier, reported shorter time in bed and earlier midpoint of sleep than those in the afternoon shift. On weekends, morning shift children went to bed later than afternoon shift. Morning shift reported greater social jetlag, shorter average sleep length and more sleep deficit than afternoon shift. During weekdays and weekends evening type children went to bed later, rose later and reported later midpoint of sleep. Also, evening type reported more social jetlag than morning types.

CONCLUSION

This study suggests that early school start times can have a detrimental effect on Mexican children. Moreover, the morning shift children may be at more risk of poor health due to the higher social jetlag, as well as a higher tendency to be sleep deprived. On the other hand, the afternoon shift represents an important social environment that allows children to follow their natural physiological needs and a more optimal sleep health.