Table 2.
Study methodology among middle schools with later start time (n = 10).
| Author | Study Description and Sampling | DST | Amount of Shift (min) | Longitudinal (within) | Cross-Sectional (between) | Length of Data Collection | Methodology |
|---|---|---|---|---|---|---|---|
| Lufi et al27 | Design: Experimental, posttest only control design Sampling: Random assignment to experimental group (n = 26) and control (n = 21) | 8:30 | 60 | Experimental group compared within participant from week 1 (began at 8:30 am) to week 2 (began at 7:30 am) | Experimental group compared between participants with control group at week 1 and week 2 | 2-week span, 5 days for each week (Saturday night– Thursday morning) | One class was randomly assigned to start school at 8:30 am during week 1 and resume at 7:30 am week 2. One class was randomly assigned to start class at 7:30 am both weeks. All participants wore an actigraph and completed sleep diaries for 2 weeks. |
| Das-Friebel et al30 | Design: Cross-sequential Sampling: Convenience | 8:00 | 20 | Two different cohorts at 3 different schools experienced a DST and were compared before and after the DST | Between participants: One cohort did not experience a DST and were compared to the 2 cohorts that did experience a DST | Before and after DST across 2013–14 and 2015–16 academic years | Data were collected twice, once before the DST and once after the DST at the end of each academic year for 2 different cohorts, including academic year 2013–14 to 2014–15 and 2014–15 to 2015–16. |
| Edwards20 | Design: Retrospective historical cross-sequential Sampling: Archival | 8:30 | 60 | Compared same students who made shift from 7:30 am to 8:30 am | Compared schools with start times ranging from 7:30 am or 8:30 am | 1999 to 2006 | Data were collected for every student in NC between 1999 and 2006 and included SST and state reading and math scores. Data was analyzed cross-sectionally and longitudinally across time. |
| Lo et al28 | Design: Prospective longitudina Sampling: Convenience | 8:15 | 45 | The same cohort of students were compared before DST, 1-month DST, and 9-month DST | Baseline (April 2016), 1-month follow-up (August 2016) and 9-month follow-up (April 2017) | Data were collected during a period of 1 month per phase data collection phase. Students completed online surveys and wore wrist actigraph for 1 week during each data collection phase. | |
| Kim et al29 | Design: Prospective longitudinal Sampling: Observational | 9:00 | 40 | The same cohort of students were compared 2-month after DST and 12-months after DST | November 2014 (2-month follow-up) and September 2015 (12-month follow-up) | Students completed questionnaires at each time point after DST. Researchers divided students into 2 groups based on whether TST increased or decreased from 2 month to 12 months. Researchers compared outcomes between the 2 different groups across time. | |
| Wolfson et al24 | Design: Cross-sectional Sampling: Random cluster selection | x | x | Compared early-starting school E (7:15 am) to late-starting school L (8:37 am) | Fall 2003 and Spring 2004 | School L and school E were from the same school district. Students at each school completed questionnaires at each data collection time point. Comparisons were made between groups across both time periods. | |
| Owens et al*17 | Design: Repeated cross-sectional Sampling: Convenience | x | x | Compared 2 different cohorts of students at the same school that advanced start time 8:00 am to 7:30 am | March 2015–June 2015 compared to March 2016–June 2016 | Students completed online surveys during the Spring term before the start time advance and after the start time advance. | |
| Lewin et al26 | Design: Retrospective case-control Sampling: Convenience | x | x | Compared 3 different SST: “earliest” (7:20–7:30), “early” (7:40–7:55), and “latest” (8:00–8:10). | 2008, 2010, 2012 annual survey | Data was collected from a publicly available data set. Survey responses were analyzed across 3 different years for 8th graders with various school start times. | |
| Temkin et al25 | Design: Cross-sectional Sampling: Convenience | x | x | Compared later SST (7:55–8:05 am for 7–8th) and earlier SST (7:20–7:25 am for 7th–12th). | Spring 2015 | Students completed online surveys and school records were obtained during the Spring 2015 term. Comparisons were made across different schools with “later” or “earlier” start times | |
| Whitaker et al18 | Design: Repeated cross-sectional Sampling: Convenience | x | x | Compared 2 different cohorts of students at the same school that advanced start time 8:00 am to 7:30 am | March 2015–June 2015 compared to March 2016–June 2016 | Students completed online surveys during the Spring term before the start time advance and after the start time advance. |
DST = delay start time, NC = North Carolina, SST = school start time, x = did not delay SST.