1996-shafii.pdf: “Nocturnal Serum Melatonin Profile in Major Depression in Children and Adolescents”, Mohammad Shafii, Duncan R. MacMillan, Mary P. Key, Ann McCue Derrick, Nancy Kaufman, Irwin D. Nahinsky (1996-11-01):
Background: In major depression, biological rhythm disturbances in sleep, appetite, and mood suggest dysregulation in neuroendocrine functions, possibly in the pineal gland. In this study, pineal gland function was examined by measuring nocturnal serum melatonin levels during both wakefulness and sleep in depressed children and adolescents.
Methods: 22 youths aged 8 to 17 years primarily with major depression were compared with 19 controls. Blood samples were drawn every half hour from 6 PM to 7 AM. Nocturnal serum melatonin levels were measured by radioimmunoassay.
Results: The overall nocturnal serum melatonin profile from 6 PM to 7 AM was statistically-significantly higher (mean±SD, 0.18±0.14nmol/
L) in the depressed group than in the controls [mean±SD, 0.15±0.10 nmol/ L, F(1,26) = 4.37, p < 0.05]. In dim light, when the subjects were awake, no difference existed between the 2 groups. After lights-out, from 10 PM to 7 AM, the melatonin profile rose in both groups; however, the depressed group had a statistically-significantly higher increase (mean±SD,0.24±0.14nmol/ L) than the controls [mean±SD,0.18±0.07nmol/ L, F(1,26) = 4.93, mean square error = 0.11, p = 0.04]. Post hoc analysis showed a statistically-significantly higher melatonin profile in depressed subjects without psychosis (n = 15) than in depressed subjects with psychosis (n = 7) or in the controls.
Conclusions: Measuring the overall nocturnal serum melatonin profile during darkness may help to differentiate children and adolescents with major depression without psychosis from those with psychosis and from controls.
2002-cardinali.pdf: “Melatonin in sleep disorders and jet-lag”, Daniel P. Cardinali, Luis I. Brusco, Santiago Pérez Lloret, Analía M. Furio (2002):
In elderly insomniacs, melatonin treatment decreased sleep latency and increased sleep efficiency. This is particularly marked in Alzheimer’s disease (AD) patients. Melatonin is effective to reduce substantially benzodiazepine use. In addition, melatonin administration synchronizes the sleep-wake cycle in blind people and in individuals suffering from delayed sleep phase syndrome or jet lag. Urinary levels of 6-sulphatoxymelatonin decrease with age and in chronic diseases like AD or coronary heart disease. The effect of melatonin on sleep is probably the consequence of increasing sleep propensity (by inducing a fall in body temperature) and of a synchronizing effect on the circadian clock (chronobiotic effect).
2002-lewy.pdf: “Low, but not high, doses of melatonin entrained a free-running blind person with a long circadian period”, Alfred J. Lewy, Jonathan S. Emens, Robert L. Sack, Brant P. Hasler, Rebecca A. Bernert (2002-02-28):
In a previous report, we were unable to entrain one out of seven totally blind people with free-running endogenous melatonin rhythms to 10 mg of exogenous melatonin. This person had the longest circadian period (24.9 h) of the group. We now find that this person can be entrained to 0.5 mg of melatonin, but not to 20 mg. These results are consistent with the idea that too much melatonin may spill over onto the wrong zone of the melatonin phase-response curve. [Keywords: circadian rhythms, free-running totally blind people, melatonin, melatonin phase-response curve]
2013-preckel.pdf: “Morningness-eveningness and educational outcomes: the lark has an advantage over the owl at high school”, Franzis Preckel, Anastasiya A. Lipnevich, Katharina Boehme, Lena Brandner, Karsten Georgi, Tanja Könen, Katharina Mursin, Richard D. Roberts (2012-01-02):
Background: Chronotype refers to individuals’ preference for morning or evening activities. Its two dimensions (morningness and eveningness) are related to a number of academic outcomes.
Aims: The main goal of the study was to investigate the incremental validity of chronotype as a predictor of academic achievement after controlling for a number of traditional predictors. In so doing, a further aim was ongoing validation of a chronotype questionnaire, the Lark-Owl Chronotype Indicator.
Sample: The sample comprised 272 students attending 9th and 10th grades at five German high schools. Data was also obtained from 132 parents of these students.
Method: Students were assessed in class via self-report questionnaires and a standardized cognitive test. Parents filled out a questionnaire at home. The incremental validity of chronotype was investigated using hierarchical linear regression. Validity of the chronotype questionnaire was assessed by correlating student ratings of their chronotype with behavioural data on sleep, food intake, and drug consumption and with parent ratings of chronotype.
Results: Eveningness was a statistically-significant (negative) predictor of overall grade point average (GPA), math-science GPA, and language GPA, after cognitive ability, conscientiousness, need for cognition, achievement motivation, and gender were held constant. Validity evidence for the chronotype measure was established by statistically-significant correlations with parent-ratings and behavioural data.
Conclusions: Results point to the possible discrimination of adolescents with a proclivity towards eveningness at school. Possible explanations for the relationship between chronotype and academic achievement are presented. Implications for educational practice are also discussed.
2014-paulsen.pdf: “Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double-blind, randomised, controlled trial”, Gøran Paulsen, Kristoffer T. Cumming, Geir Holden, Jostein Hallén, Bent Ronny Rønnestad, Ole Sveen, Arne Skaug, Ingvild Paur, Nasser E. Bastani, Hege Nymo Østgaard, Charlotte Buer, Magnus Midttun, Fredrik Freuchen, Håvard Wiig, Elisabeth Tallaksen Ulseth, Ina Garthe, Rune Blomhoff, Haakon B. Benestad, Truls Raastad (2014-03-03):
- Recent studies have indicated that antioxidant supplementation may blunt adaptations to exercise, such as mitochondrial biogenesis induced by endurance training. However, studies in humans are sparse and results are conflicting.
- Isolated vitamin C and E supplements are widely used, and unravelling the interference of these vitamins in cellular and physiological adaptations to exercise is of interest to those who exercise for health purposes and to athletes.
- Our results show that vitamin C and E supplements blunted the endurance training-induced increase of mitochondrial proteins (COX4), which is important for improving muscular endurance.
- Training-induced increases in VO2max and running performance were not detectably affected by the supplementation.
- The present study contributes to understanding of how antioxidants may interfere with adaptations to exercise in humans, and the results indicate that high dosages of vitamins C and E should be used with caution.
In this double-blind, randomised, controlled trial, we investigated the effects of vitamin C and E supplementation on endurance training adaptations in humans. Fifty-four young men and women were randomly allocated to receive either 1000 mg of vitamin C and 235 mg of vitamin E or a placebo daily for 11 weeks. During supplementation, the participants completed an endurance training programme consisting of three to four sessions per week (primarily of running), divided into high-intensity interval sessions [4–6 × 4–6 min; >90% of maximal heart rate (HRmax)] and steady state continuous sessions (30–60 min; 70–90% of HRmax). Maximal oxygen uptake (VO2max), submaximal running and a 20 m shuttle run test were assessed and blood samples and muscle biopsies were collected, before and after the intervention. Participants in the vitamin C and E group increased their VO2max (mean ± s.d.: 8 ± 5%) and performance in the 20 m shuttle test (10 ± 11%) to the same degree as those in the placebo group (mean ± s.d.: 8 ± 5% and 14 ± 17%, respectively). However, the mitochondrial marker cytochrome c oxidase subunit IV (COX4) and cytosolic peroxisome proliferator-activated receptor-γ coactivator 1 α (PGC-1α) increased in the m. vastus lateralis in the placebo group by 59 ± 97% and 19 ± 51%, respectively, but not in the vitamin C and E group (COX4: −13 ± 54%; PGC-1α: −13 ± 29%; p ≤ 0.03, between groups). Furthermore, mRNA levels of CDC42 and mitogen-activated protein kinase 1 (MAPK1) in the trained muscle were lower in the vitamin C and E group than in the placebo group (p ≤ 0.05). Daily vitamin C and E supplementation attenuated increases in markers of mitochondrial biogenesis following endurance training. However, no clear interactions were detected for improvements in VO2max and running performance. Consequently, vitamin C and E supplementation hampered cellular adaptations in the exercised muscles, and although this did not translate to the performance tests applied in this study, we advocate caution when considering antioxidant supplementation combined with endurance exercise.
2020-goldin.pdf: “Interplay of chronotype and school timing predicts school performance”, Andrea P. Goldin, Mariano Sigman, Gisela Braier, Diego A. Golombek, María J. Leon (2020-02-10):
Most adolescents exhibit very late chronotypes and attend school early in the morning, a misalignment that can affect their health and psychological well-being. Here we examine how the interaction between the chronotype and school timing of an individual influences academic performance, studying a unique sample of 753 Argentinian students who were randomly assigned to start school in the morning (07:45), afternoon (12:40) or evening (17:20). Although chronotypes tend to align partially with class time, this effect is insufficient to fully account for the differences with school start time. We show that (1) for morning-attending students, early chronotypes perform better than late chronotypes in all school subjects, an effect that is largest for maths; (2) this effect vanishes for students who attend school in the afternoon; and (3) late chronotypes benefit from evening classes. Together, these results demonstrate that academic performance is improved when school times are better aligned with the biological rhythms of adolescents.