Effects of 13-Hour 20-Minute Work Shifts on Law Enforcement Officers' Sleep, Cognitive Abilities, Health, Quality of Life, and Work Performance: The Phoenix Study

In Bell 2015, other bias was at low risk because no other potential sources of bias were identified.

“Other bias Low risk We identified no other potential sources of bias.”

Axelsson 1998 and Bell 2015 reported sleep quality off-shift.

“Axelsson 1998 and Bell 2015 reported sleep quality off‐shift.”

Bell 2015 found that both objective and subjective sleepiness scores were significantly higher in the group working shifts of 13 hours 20 minutes compared to those working 10-hour shifts, without taking unit-of-analysis error into account.

“Without taking the unit‐of‐analysis error into account, the study authors found that both scores were significantly higher in the group working shifts of 13 hours 20 minutes compared to those working 10‐hour shifts.”

Bell 2015 found that participants in the 10-hour shift group worked significantly more overtime during the six-month study period compared with participants who worked shifts of 13 hours 20 minutes (mean 9.02 versus 6.89 hours; MD 1.22, 95% CI 0.94 to 1.50).

“Participants in the 10‐hour shift group worked significantly more overtime during the six‐month study period compared with participants who worked shifts of 13 hours 20 minutes (mean 9.02 hours versus mean 6.89 hours; MD 1.22, 95% CI 0.94 to 1.50; Analysis 4.4).”

The evidence for overtime hours in Bell 2015 was of very low certainty; downgraded for imprecision, indirectness, and insufficient statistical adjustments for confounding or cluster allocation.

“This evidence was of very low certainty; we downgraded for imprecision, indirectness, and insufficient statistical adjustments for confounding or cluster allocation.”

Bell 2015 reported that participants working shifts of 13 hours 20 minutes obtained significantly fewer hours of sleep than those working 10-hour shifts, but the study authors did not take into account unit-of-analysis error.

“Bell 2015 reported that participants working shifts of 13 hours 20 minutes obtained significantly fewer hours of sleep than those working 10‐hour shifts, but the study authors did not take into account the unit‐of‐analysis error.”

Participants in Bell 2015 also worked more overtime during the year prior to the intervention.

“The participants also worked more overtime during the year prior to the intervention.”

In Bell 2015, incomplete outcome data for sleep quality off-shift was at unclear risk because the number of participants completing the study was not clearly reported.

“Incomplete outcome data (attrition bias)
Sleep quality off‐shift Unclear risk There was a clear restriction regarding the change of the work schedule. However, the number of participants completing the study was not clearly reported.”

In Bell 2015, reliability or objectivity of measurement for sleep length and quality was at unclear risk because the PSQI is a validated instrument but objective measures such as actigraphy were not used, and it is unclear whether inclusion of objective methods would have influenced results.

“Reliable or objective measurement of outcomes
Sleep length and quality Unclear risk Sleep quality and sleep length assessed by the Pittsburgh Sleep Quality Index, which is a validated instrument. However, objective measures, such as actigraphy, were not used. It is unclear whether the inclusion of objective methods would have influenced the results.”

In Bell 2015, the intervention was at low risk of affecting data collection because there were no changes in data collection.

“Intervention unlikely to affect data collection Low risk No changes in data collection.”

Bell 2015 assessed self-reported sleep quality using the Pittsburgh Sleep Quality Index at baseline and three and six months after the shift schedule change.

“Bell 2015 assessed self‐reported sleep quality using the Pittsburgh Sleep Quality Index at baseline and three and six months after the shift schedule change.”

Bell 2015 found no significant differences in sleep quality between groups at month three (mean 1.67 points, SD 0.13, in 13-hour-20-minute shifts versus mean 1.11 points, SD 0.11, in 10-hour shifts; P = 0.512; F1,348 = 0.431).

“Bell 2015 found no significant differences between the groups at month three (mean 1.67 points (SD 0.13) in those who worked shifts of 13 hours 20 minutes versus mean 1.11 points (SD 0.11) in those who worked shifts of 10 hours; P = 0.512; F1,348 = 0.431).”

At month six, Bell 2015 reported that participants working longer shifts exhibited worse sleep quality compared to those who worked shorter shifts, but this did not take into account unit-of-analysis error due to clustering.

“At month six, Bell 2015 reported that the participants working longer shifts exhibited worse sleep quality compared to those who worked shorter shifts, but this did not take into account the unit‐of‐analysis error due to clustering of participants.”

Most included studies were almost only men and focused on a few areas of work (car manufacturing, police force, maintenance unit of an airline company, power plant, and steel industry).

“Most studies included (almost) only men, and focused on a few areas of work (i.e. car manufacturing, police force, maintenance unit of an airline company, power plant, and steel industry; Amendola 2011; Axelsson 1998; Bell 2015; Garde 2020; Knauth 1998; Totterdell 1992; Viitasalo 2008).”

Two CBA trials used cluster allocation, but did not correct for unit-of-analysis error (Bell 2015; Totterdell 1992).

“Two CBA trials used cluster allocation, but did not correct for the unit‐of‐analysis error (Bell 2015; Totterdell 1992).”

In Bell 2015, blinding of outcome assessment for objective measures was at low risk because sleepiness during shifts was assessed by an objective and validated method (3-minute PVT).

“Blinding of outcome assessment (detection bias)
Objective measures Low risk Sleepiness during shifts assessed by an objective and validated method (3‐minute version of the PVT).”

In Bell 2015, selective reporting was at low risk because outcomes were reported as stated in the methods section and no reason to suspect selective reporting was found.

“Selective reporting (reporting bias) Low risk Outcomes were reported as stated in the methods session. We found no reason to suspect selective reporting.”

In Bell 2015, blinding of participants and personnel for subjective measures was at high risk because sleep length and quality were self-reported through the PSQI.

“Blinding of participants and personnel (performance bias)
Subjective measures High risk Sleep length and quality were self‐reported through the Pittsburgh Sleep Quality Index questionnaire.”

In Bell 2015, appropriateness of statistical analysis for cluster allocation was at high risk because analyses were not adjusted for the unit of analysis issues imposed by cluster allocation.

“Appropriateness of statistical analysis (cluster allocation) High risk Analyses were not adjusted for the unit of analysis issues imposed by cluster allocation.”

In Bell 2015, recruitment bias was at unclear risk because methods for allocating clusters into intervention or control groups were not explained.

“Recruitment bias Unclear risk Methods for allocating clusters into intervention or control groups were not explained.”

In Bell 2015, baseline differences between groups were at low risk because characteristics of age, sex, number of children, number of children living in the home, age of youngest child living in the home, ethnicity, and medications taken were balanced across groups.

“Baseline differences between groups Low risk The characteristics of age, sex, number of children, number of children living in the home, age of youngest child living in the home, ethnicity, and medications taken were balanced across groups.”

In Bell 2015, incomplete outcome data for sleepiness during shifts was at unclear risk because the number of participants completing the study was not clearly reported.

“Incomplete outcome data (attrition bias)
Sleepiness during shifts Unclear risk There was a clear restriction regarding the change of the work schedule. However, the number of participants completing the study was not clearly reported.”

In Bell 2015, incomplete outcome data for sleep length off-shift was at unclear risk because the number of participants completing the study was not clearly reported.

“Incomplete outcome data (attrition bias)
Sleep length off‐shift Unclear risk There was a clear restriction regarding the change of the work schedule. However, the number of participants completing the study was not clearly reported.”

In Bell 2015, reliability or objectivity of measurement for sleepiness was at low risk because sleepiness was assessed by the 3-minute version of the PVT.

“Reliable or objective measurement of outcomes
Sleepiness Low risk Sleepiness assessed by the 3‐minute version of the PVT.”

In Bell 2015, blinding of outcome assessment for subjective measures was at high risk because sleep length and quality were self-reported through the PSQI.

“Blinding of outcome assessment (detection bias)
Subjective measures High risk Sleep length and quality were self‐reported through the Pittsburgh Sleep Quality Index questionnaire.”

In Bell 2015, blinding of participants and personnel for objective measures was at low risk because sleepiness during shifts was assessed by the 3-minute version of the PVT, an objective and validated measure.

“Blinding of participants and personnel (performance bias)
Objective measures Low risk Sleepiness during shifts assessed by the 3‐minute version of the PVT, which is an objective and validate measure.”

In Bell 2015, appropriateness of statistical analyses was at low risk because multivariate analysis of variance was conducted using baseline scores as the covariate.

“Appropriateness of statistical analyses Low risk Multivariate analysis of variance was conducted, using baseline scores as the covariate.”

In Bell 2015, the intervention was at low risk of being confounded by other changes over time because no other changes were mentioned and the follow-up period was relatively short.

“Intervention independent of other changes over time Low risk No other changes mentioned in the paper. Relatively short follow‐up period; no major changes expected.”