In this blog, Emma Plugge, Cochrane UK’s Senior Fellow in Public Health looks at the evidence on later school start times for supporting students’ education and their health and wellbeing.
Page last checked 14 March 2023
If, like me, you are the parent of teenagers, you may have approached the start of the new school year with some trepidation. Perhaps you too have fantasised about a Wallace and Gromitesque contraption that propels your teenager straight from their bed to the breakfast table, dressing them efficiently on the way and thus avoiding that early morning tussle. In this case, you might be interested in the findings from a Cochrane Review Later school start times for supporting the education, health, and well‐being of high school students (published July 2017) that brings together the best available evidence to examine the impacts of a later school start time on health, education, and well-being in secondary school students.
School start times and teen sleep: a mismatch!
You might wonder why health researchers would examine an interventionA treatment, procedure or programme of health care that has the potential to change the course of events of a healthcare condition. Examples include a drug, surgery, exercise or counselling. such as the timing of the school day – what does this have to do with health? The answer is almost everything. We know that there is a mismatch between school schedules and the adolescent sleep cycle; most adolescents would naturally go to sleep late at night and wake later in the morning [Carskadon 1998]. If they are forced to wake early because they have to be at school by 8 or 9 o’clock, then they are likely to have insufficient sleep.
Sleep deprivation is linked with a number of undesirable effects on people’s health such as greater riskA way of expressing the chance of an event taking place, expressed as the number of events divided by the total number of observations or people. It can be stated as ‘the chance of falling were one in four’ (1/4 = 25%). This measure is good no matter the incidence of events i.e. common or infrequent. of accidents [Dahl 1996] and of anxiety and depression [Chorney 2007]. It’s also linked to important outcomesOutcomes are measures of health (for example quality of life, pain, blood sugar levels) that can be used to assess the effectiveness and safety of a treatment or other intervention (for example a drug, surgery, or exercise). In research, the outcomes considered most important are ‘primary outcomes’ and those considered less important are ‘secondary outcomes’. relating to academic achievement and motivation, but given the lamentable state of the mental wellbeing of today’s adolescents [Public Health England 2015], the possible positive effects of a later start time at school on children’s mental wellbeing are, arguably, sufficient in themselves to merit further investigation.
The search for wide ranging impacts – good and bad
The authors of this review looked at a broad range of family, social, educational and health outcomes – which did of course include student mental health indicators such as measures of stress, anxiety, feelings of isolation or exclusion, depression or suicidal ideation. They examined student academic outcomes measured by locally relevant standardized test scores, course grades or exam results and also student truancy or attendance rates. They recognised the potential for harm to the student and wider community by the change in school start time and so looked for any unwanted or undesirable effects such as increased transport costs for students, families or schools, and decreased student supervision outside school time.
The authors looked for a broad range of studies too, not just randomisedRandomization is the process of randomly dividing into groups the people taking part in a trial. One group (the intervention group) will be given the intervention being tested (for example a drug, surgery, or exercise) and compared with a group which does not receive the intervention (the control group). controlled trialsA trial in which a group (the ‘intervention group’) is given a intervention being tested (for example a drug, surgery, or exercise) is compared with a group which does not receive the intervention (the ‘control group’). (RCTs) which are considered to provide the best evidence and which are frequently the only type of studyAn investigation of a healthcare problem. There are different types of studies used to answer research questions, for example randomised controlled trials or observational studies. included in Cochrane ReviewsCochrane Reviews are systematic reviews. In systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research.. They included non-randomisedA non-randomised study is any quantitative study estimating the effectiveness of an intervention (harm or benefit) that does not use randomisation to allocate people to comparison groups. designs such as controlled before and after studies. In this sort of study, measurements of outcomes such as students’ mental wellbeing or academic performance, are made before there is any change to the start of the school day in two groups of students – those who are going to receive the intervention and those who are not. An appropriate time after the intervention (in this case the change in the school start time), these measurements are taken again in both sets of students and compared.
The need for public engagement/consumer involvement in study design?
The authors found 11 unique studies with almost 300,000 participants aged 13 to 19 years. One of the interesting findings for me was the nature of the interventions – just how late did the school day start? In many studies the adjusted school day still did not start very late. For example, studies reported the differences between starting school at 8am rather than 7am. In only two studies did the school start time shift to 10 or 10.30 although in another study students were taught in the afternoons only. It would be interesting to ask teenagers their views of these ‘interventions’ and whether such small changes (shifting the start time from 7am to 8am, for example) are perceived as meaningful. There is undoubtedly a need for the ‘consumers’ to be involved in the study design!
Sometimes the change is beneficial, sometimes not…
Four studies examining the associationA relationship between two characteristics, such that as one changes, the other changes in a predictable way. For example, statistics demonstrate that there is an association between smoking and lung cancer. In a positive association, one quantity increases as the other one increases (as with smoking and lung cancer). In a negative association, an increase in one quantity corresponds to a decrease in the other. Association does not necessarily mean that one thing causes the other. between later school start times and academic outcomes reported mixed results; two studies reported a positive association between a later start and academic outcomes. One study reported a negative association, the later school starts led to poorer academic achievement. The results were inconclusive in the fourth study.
There were also mixed results from the studies examining the association between later school start times and student alertness and those measuring absenteeism. There were six studies that looked at the total amount of sleep and these consistently reported a significant, positive association between a later school start time and amount of sleep.
Surprisingly only one study looked at mental health outcomes, reporting an association between decreased depressive symptoms and later school start times.
The authors did find reports of unwanted effects – for example less interaction between parents and children, and staffing and scheduling difficulties. However – and this is a really important however- for all outcomes (the positive ones as well as the negative ones), the quality of the evidenceThe certainty (or quality) of evidence is the extent to which we can be confident that what the research tells us about a particular treatment effect is likely to be accurate. Concerns about factors such as bias can reduce the certainty of the evidence. Evidence may be of high certainty; moderate certainty; low certainty or very-low certainty. Cochrane has adopted the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation) for assessing certainty (or quality) of evidence. Find out more here: https://training.cochrane.org/grade-approach was very low which means it was not possible to draw any firm conclusions for or against later school start times.
So the authors concluded that they could not determine the effects of later school start times with any confidence although they did suggest there might be ‘potential benefits’. They highlighted the need for further research, for ‘RCT and rigorous quasi-experimental designs (when RCTs are not feasible) exploring the effects of standard later school start time interventions on standardized outcomes, so that a broader evidence base can be put into place.’ Great. I am sure my family would be happy to participate in any such trialClinical trials are research studies involving people who use healthcare services. They often compare a new or different treatment with the best treatment currently available. This is to test whether the new or different treatment is safe, effective and any better than what is currently used. No matter how promising a new treatment may appear during tests in a laboratory, it must go through clinical trials before its benefits and risks can really be known.. But make sure the adjusted school day begins more than a single hour later and please don’t put us in the control arm…
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References may be found here.
Emma Plugge has nothing to disclose.