Debate on daylight saving time and school start time

April 22, 2019

Science Daily/University of Surrey

A switch to permanent daylight saving time will undo any positive effects on sleep of delaying school start times, according to researchers from the University of Surrey.

Writing in the journal Current Biology, Professor Anne Skeldon and Professor Derk-Jan Dijk discuss proposals by the California state legislature to introduce permanent daylight saving time (DST) and how this switch could undermine a 2018 vote in the state to delay school start time for teenagers. The vote last year in the California legislature, currently vetoed by the State Governor, prohibited the start of schools before 8:30am in a bid to improve student health and boost graduation rates.

Delaying school times has been a contentious issue in North America and Europe with proponents arguing that such a postponement would enable teenagers, who typically go to bed later, to get the recommended amount of sleep, whilst opponents point to the logistical problems that would arise from such a change. DST, the practice of setting the clocks forward one hour from standard time (ST) during the summer months in order to make better use of natural daylight, is also a divisive issue. In March, the European parliament voted to stop changing the clocks, with European Union member states required to decide whether to stay on permanent DST or permanent ST by 2021. California, Florida and Washington are all due to vote on whether to stay on permanent DST. Skeldon and Dijk point out that a switch to permanent DST is incompatible with the aims of delaying school times.

They note that a later biological wake time under permanent DST undermines the benefits of delaying school start times on the sleep of teenagers. For example, from a biological perspective, teenagers would find it as hard to get up at 7am under DST as getting up at 6am during. Skeldon and Dijk conclude that the introduction of permanent DST and delaying school start times are contradictory, as teenagers would, on average, lose any sleep benefit gained from a later school start time as a result of the shift to permanent DST, meaning they'd still be getting inadequate levels of sleep.

Professor Skeldon, from the Department of Mathematics, said: "Each spring, altering the clocks prompts debate. We enjoy the sudden change to lighter evenings, but we do not find the shift to our schedules easy. However, for our sleep, permanent DST is not the solution. Setting our clocks to DST during the winter month's means that the sun will appear to rise one hour later, leaving even more of us to get up in the hours of darkness. Of course, for those who live predominantly inside, rarely experiencing natural light, a switch to permanent DST will have less of an impact. But these people will also only see limited benefits from delaying school/work start times.

"It is complicated, but the impact of switching to permanent daylight saving time on adolescent sleep appears to have been neglected in these considerations."

Professor Dijk, Director of the Surrey Sleep Research Centre, commented: "Many of us are confused about clock and circadian time, but for the sake of our health and well-being it is about time we get our heads around it."

https://www.sciencedaily.com/releases/2019/04/190422112809.htm

Postnatal depression could be linked to fewer daylight hours during late pregnancy

Shortening days during third trimester of pregnancy may add to risk of postpartum depression

September 27, 2018

Science Daily/Springer

Women in late pregnancy during darker months of the year may have a greater risk of developing postpartum depression once their babies are born. This is consistent with what is known about the relationship between exposure to natural light and depression among adults in the general population.

Although reduced exposure to natural light has been associated with depression among adults in the general population, there is not yet a consensus about whether light exposure or seasonality influences the development of depression during and after pregnancy.

In this study, Goyal and her colleagues at the University of California San Francisco analysed available information from 293 women who participated in one of two randomized controlled clinical trials about sleep before and after pregnancy. The participants were all first-time mothers from the US state of California. Data included the amount of daylight during the final trimester of their pregnancy, along with information about known risk factors such as a history of depression, the woman's age, her socioeconomic status and how much she slept.

Overall, the participants had a 30 per cent risk of depression. The analysis suggested that the number of daylight hours a woman was exposed to during her final month of pregnancy and just after birth had a major influence on the likelihood that she developed depressive symptoms.

The lowest risk for depression (26 per cent) occurred among women whose final trimester coincided with seasons with longer daylight hours. Depression scores were highest (35 per cent) among women whose final trimester coincided with "short" days and the symptoms continued to be more severe following the birth of their babies in this group of women. In the northern hemisphere, this timeframe refers to the months of August to the first four days of November (late summer to early autumn).

"Among first-time mothers, the length of day in the third trimester, specifically day lengths that are shortening compared to day lengths that are short, long or lengthening, were associated with concurrent depressive symptom severity," Goyal explains.

The findings suggest that using light treatment in the late third trimester when seasonal day length is shortening could minimize postpartum depressive symptoms in high-risk mothers during the first three months of their children's lives. Goyal says that women with a history of mental health problems and those who are already experiencing depressive symptoms in the third trimester might further benefit from being outdoors when possible, or using devices such as light boxes that provide light therapy.

"Women should be encouraged to get frequent exposure to daylight throughout their pregnancies to enhance their vitamin D levels and to suppress the hormone melatonin," adds Goyal, who says that clinicians should also advise their patients to get more exercise outdoors when weather and safety permit. "Daily walks during daylight hours may be more effective in improving mood than walking inside a shopping mall or using a treadmill in a gym. Likewise, early morning or late evening walks may be relaxing but would be less effective in increasing vitamin D exposure or suppressing melatonin."

https://www.sciencedaily.com/releases/2018/09/180927105733.htm

Fish-rich diets in pregnancy may boost babies' brain development

September 20, 2018

Science Daily/Springer

Women could enhance the development of their unborn child's eyesight and brain function by regularly eating fatty fish during pregnancy. This is the suggestion from a small-scale study. The research supports previous findings that show how important a prospective mother's diet and lifestyle choices are for the development of her baby.

According to Laitinen, a mother's diet during pregnancy and breastfeeding is the main way that valuable long-chain polyunsaturated fatty acids become available to a fetus and infant brain during the period of maximum brain growth during the first years of a child's life. Such fatty acids help to shape the nerve cells that are relevant to eyesight and particularly the retina. They are also important in forming the synapses that are vital in the transport of messages between neurons in the nervous system.

In this study, Laitinen and her colleagues analysed the results of 56 mothers and their children drawn from a larger study. The mothers had to keep a regular food diary during the course of their pregnancy. Fluctuations in their weight before and during pregnancy were taken into account, along with their blood sugar level and blood pressure. Aspects such as whether they smoked or developed diabetes related to pregnancy were also noted.

The team recorded the levels of nutritional long-chain polyunsaturated fatty acid sources in the mother's diet and blood serum, and the levels in the blood of their children by the age of one month. Their children were further tested around their second birthday using pattern reversal visual evoked potentials (pVEP). This sensitive and accurate, non-invasive method is used to detect visual functioning and maturational changes occurring within a young child's visual system.

The subsequent analyses of the visual test results revealed that infants whose mothers ate fish three or more times a week during the last trimester of their pregnancy fared better than those whose mothers ate no fish or only up to two portions per week. These observations were further substantiated when the serum phospholipid fatty acid status was evaluated.

"The results of our study suggest that frequent fish consumption by pregnant women is of benefit for their unborn child's development. This may be attributable to long-chain polyunsaturated fatty acids within fish, but also due to other nutrients like vitamin D and E, which are also important for development," explains Laitinen.

"Our study therefore highlights the potential importance of subtle changes in the diet of healthy women with uncompromised pregnancies, beyond prematurity or nutritional deficiencies, in regulating infantile neurodevelopment," adds Laitinen, who believes that their results should be incorporated into counselling given to pregnant women about their diets.

https://www.sciencedaily.com/releases/2018/09/180920102207.htm