AMERICAN JOURNAL OF INDUSTRIAL MEDICINE 58:464–471 (2015)
Brief Report
Reduced Sleep Duration and History of Work-Related Injuries Among Washington State Adolescents with a History of Working Janessa M. Graves, PhD MPH1 and Mary E. Miller, MN RN2
Background The relationship between sleep and occupational injury risk has not been adequately explored for working adolescents. Methods Data were analyzed from the 2010 Washington State Healthy Youth Survey of 8th, 10th, and 12th grade public school students. Teens reported average school and weekend night sleep hours and history of work-related injury that received medical treatment. Multivariable logistic regression evaluated the association between sleep duration and occupational injury. Results Of 4,144 working teens, 6.4% reported ever having an occupational injury. Teens who sleep 5 hr/school night had greater odds of a history of occupational injury than those sleeping 8 hr (OR:2.91, 95% CI:1.85–4.57). No significant association was observed for weekend night sleep duration. Conclusions Reduced school night sleep was associated with increased odds of workrelated injury in adolescents. Long hours and late night schedules may contribute to decreased sleep time and potentially have other health and developmental impacts for youth. Am. J. Ind. Med. 58:464–471, 2015. ß 2015 Wiley Periodicals, Inc. KEY WORDS: adolescent; employment; sleep; injury; occupational injuries
INTRODUCTION Decreased sleep duration and altered sleep schedules have been long associated with multiple adverse outcomes, including disrupted circadian rhythms; increased daytime sleepiness; poor academic performance; heightened stress and anxiety; weight gain; mood and behavior problems; negative health behaviors, such as tobacco and alcohol use;
1
College of Nursing (Spokane), Washington State University, Spokane, Washington Washington State Department of Labor and Industries, Olympia, Washington *Correspondence to: Janessa M. Graves, PhD MPH, Washington State University, College of Nursing-Spokane, P.O. Box 1495, Spokane, WA 99210-1495. E-mail: [email protected] 2
Accepted 21 November 2014 DOI 10.1002/ajim.22416. Published online 24 February 2015 in Wiley Online Library (wileyonlinelibrary.com).
ß 2015 Wiley Periodicals, Inc.
and increased illness episodes and longer recovery [Carskadon et al., 2004; O’Brien and Mindell 2005; Cappuccio et al., 2008; Orzech et al., 2014]. Work intensity and duration contribute to reduced or disrupted sleep and day-time sleepiness [Rosa, 2002]. In addition to these impacts, lack of sleep and long work hours have been associated with increased fatigue and occupational injury risk [Lombardi et al., 2010; Arlinghaus et al., 2012; Uehli et al., 2013]. Lombardi and colleagues identified a dose-response relationship between sleep duration and the odds of work-related injury among adults in the National Health Interview Survey [Lombardi et al., 2010]. Federal child labor rules do not restrict work hours for 16- and 17-year olds (regardless of school year or summer time) and have no restrictions for any child or adolescent working in agriculture. However, a number of states have additional child labor regulations, such as Washington, that
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help ensure a balance between work, school, and other important activities for youth [Washington State Legislature, 1990, 2003]. These child labor regulations limit the hours of work for youth based on age and differ during school weeks and non-school weeks; school day versus a non-school day; and specify the number of work hours per day and per week, the number of work days per week, and how early or late teens may work. Limiting work hours also contributes toward protecting adolescent sleep needs. Research studies have illustrated the relationship between extended hours of work and decreased sleep duration in adults [Basner et al., 2007; Artazcoz et al., 2009; Nakashima et al., 2011]. Among adolescents, increased daily work duration and late night shifts negatively impact night-time sleep duration [Fischer et al., 2008]. Adolescents’ increased need for sleep [Carskadon, 2002], together with school, sports and other recreation and family activities, and part-time work, may not only interfere with the need for more sleep, but also may contribute to negative impacts, including injury. However, the relationship between sleep and occupational injury risk has not been adequately explored in adolescent workers. Recently, experts in occupational injury prevention and adolescent development have highlighted the importance of this issue and called for additional research in this area [Runyan et al., 2013]. This study evaluates the association between decreased sleep duration and lifetime occupational injury among adolescents with a history of working in Washington State.
MATERIALS AND METHODS Study Sample This cross-sectional, population-based cohort study used data collected for the 2010 state-wide Washington State Healthy Youth Survey (HYS). Using a clustered sampling design, this survey is administered to students in 6th, 8th, 10th, and 12th grade classrooms on even years. Students in the older grades take a two-form “interleaved” survey with core questions and two questionnaires that are randomly distributed. The 6th grade survey consists of a single-form, shorter version with fewer questions. This study evaluates results from the 2010 HYS Form B, a form of the questionnaire that included questions on sleep and work experience. Responses are anonymous and participation is voluntary for schools and students.
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around your home, while working for pay, have you ever been injured badly enough that you needed to go to a nurse, doctor, or hospital?” Possible responses included “Never worked for pay,” “Have worked, but never been injured enough to see a nurse or doctor,” and “Yes, I was injured at work and needed to go to a nurse, doctor or hospital.” A student was considered having ever had a work-related injury if they selected the latter response. The total number of students reported having ever worked was calculated by combining the students who reported having worked but never been injured and those who reported ever being injured at work.
Independent variables School night sleep duration was self-reported and ascertained from the question in the 2010 HYS Form B, “On an average school night, how many hours do you sleep?” Average weekend night sleep duration was estimated using this following question: “On an average weekend night (Friday or Saturday), how many hours do you sleep?” Both variables were originally categorized as “5 hr or less,” “about 6 hr,” “about 7 hr,” “about 8 hr,” and “9 hr or more;” for analyses, “about 6 hr” and “about 7 hr” were combined into a single category.
Covariates Analyses included demographic information reported by students in the 2010 HYS Form B, including grade (8th [reference], 10th, 12th), age (categorized as 12 or younger, 13–15 [reference], 16–17, and 18 or older), gender (male [reference], female), race/ethnicity (non-Hispanic White [reference], non-Hispanic Black, Hispanic or Latino/a, or other/unknown/multiple), language spoken at home (English [reference], non-English), maternal education (12 or fewer years, more than 12 years [reference], missing), living situation (with parent or guardian or elsewhere [reference], which could include the following locations: friend’s house, motel/hotel, shelter, car, campground, or on their own), and student assessment of academic performance in the previous year (“Putting them all together, what were your grades like last year?”). Models also included the following potential confounders: lifetime alcohol use (“Have you ever had more than a sip or two of beer, wine, or hard liquor?”; responses were coded as yes [reference] or no, and days per week engaged in supervised after-school activities (0 days, 1–2 days, or 3 or more days [reference]).
Measures Dependent variable
Statistical Analyses
Adolescent work-related injury was assessed from the question in the 2010 HYS Form B, “NOT counting chores
Variables were described across adolescents who reported having a work-related injury and those who did
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not; bivariate comparisons were made using chi-squared tests. We used multivariable logistic regression models to evaluate the association between average sleep duration and report of ever having a work-related injury. The covariates listed above were included in all models, except for grade, which was correlated with age. We used Stata/MP v.13.0 for all analyses, including svy commands to account for the complex survey design. Because it involves analysis of de-identified data, this study was determined to be exempt from review by the Washington State Institutional Review Board.
RESULTS The 2010 HYS was completed by 22,520 students in the state-wide sample; overall response rates were 77%, 67%, and 53% for 8th, 10th, and 12th grades respectively. The HYS Form B with questions about work injury and sleep was completed by 11,222 students in 2010. A total of 4,175 (37.2%) students responding to Form B, reported having ever worked for pay outside of the home. Students with a history of working for pay more often reported fewer school and weekend night sleep hours than students with no history of working (Fig. 1, chi2 test, P < 0.01). To construct the final study sample, we excluded students who were missing data for the independent variable
describing school night sleep duration (n ¼ 31, 0.7%). The final study sample included 4,144 students in 8th (29.7%), 10th (29.2%) and 12th (41.1%) grades (Table I). Of the study sample, 6.4% (N ¼ 265) reported ever seeking treatment from a nurse, doctor, or hospital for a work-related injury. Work-related injury history varied significantly by grade, sex, age, race/ethnicity, maternal education, living situation, academic grades, and alcohol use (chi2 tests, P < 0.01). Among adolescents with a history of working, those who reported ever seeking treatment for a work-related injury indicated sleeping for 5 or fewer hours on an average school night more frequently than their working peers without a history of injury (Table II). A similar pattern was observed for average weekend night sleep duration. Multivariable logistic regression results indicate that compared to adolescents who reported sleeping about 8 hr on a school night, those who sleep 5 or fewer hours have a 1.91 times increased odds of ever having had a work-related injury for which medical treatment was sought (OR: 2.91, 95% CI: 1.85–4.57) (Table III). Those who reported sleeping about 6–7 hr on school nights also had a higher odds of reporting a history of a work-related injury compared to students who reported sleeping 8 hr, after adjusting for covariates (OR 1.52, 95:CI: 1.03–2.23). No significant association was observed between average weekend night sleep duration and the odds of ever having had a work-related injury for which medical treatment was sought (Table III).
School and Weekend Night Sleep Duration by Student Work History 60% 53%
50% 46%
Proportion of Students
43% 40%
38%
32% 30%
27% 23%
22%
21% 20%
20%
16% 11%
12%
17%
11% 9%
10%
0% 5 hr or less
About 6-7 hr
About 8 hr
9 hr or more
5 hr or less
School night
About 6-7 hr
About 8 hr
Weekend night Never worked
Ever worked
FIGURE 1. Self-reported average school and weekend night sleep duration among students who reported a history of every working for pay and students who never worked, Washington State Healthy Youth Survey, 2010.
9 hr or more
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TABLE I. Characteristics of Adolescents by Work-Related Injury History, Washington State Healthy Youth Survey, 2010 Ever sought medical treatment for a work-related injurya Characteristic
Yes (N ¼ 265)
No (N ¼ 3879)
110 (41.5) 73 (27.6) 82 (30.9)
1121 (28.9) 1137 (29.3) 1621 (41.8)
175 (66.3) 89 (33.7)
1993 (51.4) 1885 (48.6)
3 (1.1) 156 (58.9) 68 (25.7) 38 (14.3)
11 (0.3) 1878 (48.4) 1541 (39.8) 447 (11.5)
126 (51.9) 23 (9.5) 55 (22.6) 39 (16.1)
2373 (67.0) 154 (4.4) 496 (14.0) 518 (14.6)
98 (37.6) 122 (46.7) 41 (15.7)
2077 (53.9) 1287 (33.4) 491 (12.7)
200 (74.5) 65 (24.5)
3660 (94.4) 219 (5.6)
76 (29.3) 76 (29.3) 57 (22.0) 19 (7.3) 31 (12.0)
1471 (38.3) 1350 (35.1) 740 (19.3) 184 (5.8) 99 (2.6)
62 (23.6) 201 (76.4)
1339 (34.7) 2523 (65.3)
112 (42.2) 54 (20.4) 99 (37.4)
1445 (37.4) 796 (20.6) 1620 (42.0)
b
Grade 8th 10th 12th Sexb Male Female Ageb 12 or younger 13^15 years 16^17 years 18 or older Race/Ethnicityb Non-Hispanic White Non-Hispanic Black Hispanic or Latino/a Other Maternal educationb < ¼ 12 years >12 years Data missing Living situationb With parents or guardian Elsewhere Typical gradesb Mostly A’s Mostly B’s Mostly C’s Mostly D’s Mostly F’s Ever consumed alcoholb Yes No Days per week engaged in after school activities 0 days 1^2 days 3 or more days
Values indicate N (%). a Work-related injury is characterized by respondent indicating that, while working for pay (not counting chores around their home), he/she had you ever been injured badly enough that you needed to go to a nurse, doctor, or hospital. b Chi-squared test comparing distribution of students with work-related injuries across characteristics, P < 0.01.
DISCUSSION Young workers, particularly those under age 18, are at increased risk for occupational injuries compared to their adult counterparts [Institute of Medicine and National Research Council, 1998; Miller and Kaufman, 1998; Castillo
et al., 1999; Weller et al., 2003; Salminen, 2004; Windau and Meyer 2005; Zierold and Anderson, 2006; Centers for Disease Control and Prevention, 2010; Rauscher et al., 2011; Miller 2012]. This study found that among teens with a history of working, reduced sleep duration was associated with increased odds of ever having a work-related injury.
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TABLE II. Self-Reported Sleep Duration Among Adolescents With and Without a History of a Work-Related Injury, Washington State Healthy Youth Survey, 2010 Ever sought medical treatment for a work-related injurya Yes (N ¼ 265)
No (N ¼ 3879)
b
Average school night sleep duration 5 or fewer hours 64 (24.2) About 6^7 hr 128 (48.3) About 8 hr 43 (16.2) 9 or more hours 30 (11.3) Average weekend night sleep durationb 5 or fewer hours 78 (29.8) About 6^7 hr 65 (24.8) About 8 hr 52 (19.9) 9 or more hours 67 (25.6)
414 (10.7) 2063 (53.2) 1078 (27.8) 324 (8.4) 629 (16.3) 889 (23.1) 848 (22.0) 1488 (38.6)
Values indicate N (%). a Work-relatedinjuryischaracterizedbyrespondentindicatingthat,whileworkingfor pay (not counting chores around their home),he/she had you ever been injuredbadly enough that you needed to go to a nurse, doctor, or hospital. b Chi-squared test comparing distribution of students with work-related injuries across levels of sleep, P < 0.01.
Previous research supports the relationship between engagement in work and adolescent sleep patterns [Carskadon 1990; Teixeira et al., 2004; Teixeira et al., 2006; Fischer et al., 2008]. Teixeira and colleagues’ evaluation of working students in Sao Paulo, Brazil found evidence of poorer sleep quality, chronic sleep debt, shorter sleep duration, and increased sleepiness among working students, compared to their non-working peers [Teixeira et al., 2004, 2006]. Similarly, Fischer and colleagues reported that among adolescents attending evening classes, working was significantly associated with shorter sleep duration during the week, and working 8–10 hr/day was associated with longer, rebound sleep on the weekends.[Fischer et al., 2008] Although the 2010 HYS did not ask teens about working multiple jobs, Zierold and colleagues found that those working more than one job were more likely to work past 11 p.m. and work more than 40 hr per week and were 1.6 times more likely to be injured at work [Zierold et al., 2011]. While the injury finding in Zierold et al., 2011 was not statistically significant, the possibility of working more than one job should not be excluded as a contributing factor in our results. In addition, although this study did not ask about youth working in their family’s business, previous research suggests that those working in their family’s business reported performed more hazardous work and suffered more severe injuries than teens working for other employers [Zierold et al., 2012]. While this study found a significant relationship between school night sleep duration and work-related injury
history, no relationship with weekend sleep duration was identified. It is not unusual for adolescents to report shorter sleep durations during school nights compared to weekends [Wolfson and Carskadon, 1998; Crowley and Carskadon, 2010] and it has been suggested that adolescents may sleep longer on weekends in order to compensate for insufficient sleep during the week [Fischer et al., 2008; Liu et al., 2008]. Such weekend “catch-up” sleep may reflect actual sleep needs of adolescents. Insufficient school night sleep and weekend bedtime delays are associated with daytime sleepiness and changes in function, including depressive mood and risk-taking behavior [Wolfson and Carskadon, 1998; O’Brien and Mindell, 2005]. While we were not able to assess weekend sleep schedule delays in this study, it may be possible that the relationship between weekday and weekend sleep duration could contribute to occupational injury among working teens. Many have pointed toward the injury risks associated with sleep deprivation in this population, however, to our knowledge, this is the first study to examine this relationship in adolescents. In adults, poor sleep quality, sleep problems, reduced sleep duration, and early waking hours are known risk factors for occupational injuries [Uehli et al., 2013, 2014; Chiu et al., 2014]. A recent literature review concluded that among workers aged 16–70 years, approximately 13% of work-related injuries could be attributed to sleep problems [Uehli et al., 2014]. In adolescents, however, the relationship between sleep problems and work-related injuries has thus far been inadequately explored. This study contributes to the literature by describing the potential impact of school night and weekend sleep duration on injury risk in teens. An ancillary finding of this study may warrant future investigation. Compared to older students, a higher proportion of 8th grade students reported ever having a work-related injury (Table I). This finding is alarming, given that most 8th graders would typically be below the legal age of work and their lifetime exposure to work should be less than older students. This study has several limitations. First, the reported occupational injuries among the surveyed adolescents were relatively infrequent. Accordingly, the HYS asked students to report their lifetime (“ever”) work-related injury experience. Sleep duration is reported contemporaneously. This study assumes that average sleep duration does not change over time. Given the cross-sectional nature of this study, it is only feasible to evaluate the association between sleep duration and occupational injury, not causation. It is possible that an occupational injury, such as a head injury or other injury resulting in pain or disability, could impact sleep [Kaufman et al., 2001; Pillar et al., 2003]; however, we were not able to investigate the potential directionality of the association. Second, in addition to sleep duration, sleep quality has been associated with poorer health and
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TABLE III. Association Between Self-Reported Average School and Weekend Night Sleep Duration and History of a Work-Related Injury, Washington State Healthy Youth Survey, 2010
Average school night sleep duration 5 or fewer hours About 6^7 hr About 8 hr 9 or more hours Average weekend night sleep duration 5 or fewer hours About 6^7 hr About 8 hr 9 or more hours Sex Male Female Age 12 or younger 13^15 years 16^17 years 18 or older Race/Ethnicity Non-Hispanic White Non-Hispanic Black Hispanic or Latino/a Other Maternal education < ¼ 12 years >12 years Data missing Living situation With parents or guardian Elsewhere Typical grades Mostly A’s Mostly B’s Mostly C’s Mostly D’s Mostly F’s Ever consumed alcohol Yes No Days per week engaged in after school activities 0 days 1^2 days 3 or more days
Adjusted OR (95% CI)
Adjusted OR (95% CI)
2.91 (1.85^4.57) 1.52 (1.03^2.23) Reference 1.60 (0.96^2.64)
ç ç ç ç
ç ç ç ç
1.19 (0.75^1.88) 0.95 (0.63^1.43) Reference 0.64 (0.42^1.00)
Reference 0.53 (0.38^0.74)
Reference 0.55 (0.40^0.77)
1.93 (0.40^9.29) Reference 0.56 (0.40^0.78) 0.91 (0.58^1.43)
2.32 (0.54^10.00) Reference 0.61 (0.44^0.84) 0.96 (0.63^1.48)
Reference 1.44 (0.82^2.53) 1.60 (1.09^2.33) 1.07 (0.72^1.60)
Reference 1.46 (0.81^2.61) 1.51 (1.03^2.22) 1.07 (0.71^1.60)
Reference 1.41 (1.05^1.90) 1.19 (0.76^1.86)
Reference 1.44 (1.07^1.93) 1.22 (0.77^1.91)
Reference 3.63 (2.46^5.34)
Reference 3.77 (2.56^5.54)
Reference 0.86 (0.63^1.18) 1.01 (0.67^1.53) 0.91 (0.52^1.59) 1.85 (1.01^3.39)
Reference 0.83 (0.60^1.14) 0.98 (0.65^1.49) 1.00 (0.60^1.69) 1.95 (1.04^3.67)
Reference 1.56 (1.11^2.21)
Reference 1.55 (0.59^1.13)
0.81 (0.59^1.12) 0.76 (0.48^1.19) Reference
0.81 (0.59^1.13) 0.78 (0.50^1.22) Reference
CI, confidence interval; OR, odds ratio. OR estimates were adjusted for age sex race/ethnicity maternal education living situation typical grades lifetime alcohol use and after school activities.
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academic outcomes in adolescents [Javaheri et al., 2008; Short et al., 2013] and possibly occupational injury in adults [Uehli et al., 2013]. Sleep quality was not ascertained in the HYS and therefore we cannot measure that impact in this study, however we acknowledge it may also be a contributing factor to negative impacts found in other studies. Similarly, we do not have data regarding fatigue or exhaustion, both of which can influence workrelated injury risk. The 2010 HYS did not ask students the type of job in which they were engaged when they were injured, or did it include questions on work hours or work in multiple jobs. These factors are critical and should be considered in future surveys. Finally, data gathered in any survey study, such as this one, are self-reported by the teens and not validated by another method. The anonymous and voluntary nature of the survey reduce the likelihood of fabricated or falsified responses, however, it does not preclude social desirability bias [Groves et al., 2009]. It is unlikely, however, that these effects would substantially impact the results of this study [Fan et al., 2006]. Working adolescents experience the benefits of the working world, including the opportunity to earn an income and learn skills necessary for positive career development. However, there are hazards and risks associated with work, particularly for teens. Young workers also experience deleterious outcomes of work, both directly, such as injuries [Centers for Disease Control and Prevention, 2010] and workplace violence [Rauscher, 2008], and indirectly, such as increased substance use, poor school performance [Warren and Lee, 2003; Staff et al., 2010; Osilla et al., 2013], and decreased sleep duration, as our data show. This research suggests that reduced sleep duration may be associated with work-related injuries among working teens. It is crucial to consider not only the injury risks, but also the health, well-being, and psychosocial impacts associated with adolescent work. Work schedules for youth must be kept in balance with their developmental needs and other equally important ageappropriate activities. Additional research to better understand the influence of long work hours and late night work schedules on these outcomes among adolescents is warranted. Also, existing child labor regulations that limit work hours for youth must be followed and policies should be developed to address the gaps that currently exist.
ACKNOWLEDGMENTS Authors would like to thank Lillian S. Bensley, PhD, MS at the Washington State Department of Health for her assistance in obtaining and understanding the HYS dataset. Authors have no conflicts of interest to declare, including relevant financial interests, activities, relationships, and affiliations.
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Disclosure Statement: The authors report no conflicts of interests.
Brief Report
Reduced Sleep Duration and History of Work-Related Injuries Among Washington State Adolescents with a History of Working Janessa M. Graves, PhD MPH1 and Mary E. Miller, MN RN2
Background The relationship between sleep and occupational injury risk has not been adequately explored for working adolescents. Methods Data were analyzed from the 2010 Washington State Healthy Youth Survey of 8th, 10th, and 12th grade public school students. Teens reported average school and weekend night sleep hours and history of work-related injury that received medical treatment. Multivariable logistic regression evaluated the association between sleep duration and occupational injury. Results Of 4,144 working teens, 6.4% reported ever having an occupational injury. Teens who sleep 5 hr/school night had greater odds of a history of occupational injury than those sleeping 8 hr (OR:2.91, 95% CI:1.85–4.57). No significant association was observed for weekend night sleep duration. Conclusions Reduced school night sleep was associated with increased odds of workrelated injury in adolescents. Long hours and late night schedules may contribute to decreased sleep time and potentially have other health and developmental impacts for youth. Am. J. Ind. Med. 58:464–471, 2015. ß 2015 Wiley Periodicals, Inc. KEY WORDS: adolescent; employment; sleep; injury; occupational injuries
INTRODUCTION Decreased sleep duration and altered sleep schedules have been long associated with multiple adverse outcomes, including disrupted circadian rhythms; increased daytime sleepiness; poor academic performance; heightened stress and anxiety; weight gain; mood and behavior problems; negative health behaviors, such as tobacco and alcohol use;
1
College of Nursing (Spokane), Washington State University, Spokane, Washington Washington State Department of Labor and Industries, Olympia, Washington *Correspondence to: Janessa M. Graves, PhD MPH, Washington State University, College of Nursing-Spokane, P.O. Box 1495, Spokane, WA 99210-1495. E-mail: [email protected] 2
Accepted 21 November 2014 DOI 10.1002/ajim.22416. Published online 24 February 2015 in Wiley Online Library (wileyonlinelibrary.com).
ß 2015 Wiley Periodicals, Inc.
and increased illness episodes and longer recovery [Carskadon et al., 2004; O’Brien and Mindell 2005; Cappuccio et al., 2008; Orzech et al., 2014]. Work intensity and duration contribute to reduced or disrupted sleep and day-time sleepiness [Rosa, 2002]. In addition to these impacts, lack of sleep and long work hours have been associated with increased fatigue and occupational injury risk [Lombardi et al., 2010; Arlinghaus et al., 2012; Uehli et al., 2013]. Lombardi and colleagues identified a dose-response relationship between sleep duration and the odds of work-related injury among adults in the National Health Interview Survey [Lombardi et al., 2010]. Federal child labor rules do not restrict work hours for 16- and 17-year olds (regardless of school year or summer time) and have no restrictions for any child or adolescent working in agriculture. However, a number of states have additional child labor regulations, such as Washington, that
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help ensure a balance between work, school, and other important activities for youth [Washington State Legislature, 1990, 2003]. These child labor regulations limit the hours of work for youth based on age and differ during school weeks and non-school weeks; school day versus a non-school day; and specify the number of work hours per day and per week, the number of work days per week, and how early or late teens may work. Limiting work hours also contributes toward protecting adolescent sleep needs. Research studies have illustrated the relationship between extended hours of work and decreased sleep duration in adults [Basner et al., 2007; Artazcoz et al., 2009; Nakashima et al., 2011]. Among adolescents, increased daily work duration and late night shifts negatively impact night-time sleep duration [Fischer et al., 2008]. Adolescents’ increased need for sleep [Carskadon, 2002], together with school, sports and other recreation and family activities, and part-time work, may not only interfere with the need for more sleep, but also may contribute to negative impacts, including injury. However, the relationship between sleep and occupational injury risk has not been adequately explored in adolescent workers. Recently, experts in occupational injury prevention and adolescent development have highlighted the importance of this issue and called for additional research in this area [Runyan et al., 2013]. This study evaluates the association between decreased sleep duration and lifetime occupational injury among adolescents with a history of working in Washington State.
MATERIALS AND METHODS Study Sample This cross-sectional, population-based cohort study used data collected for the 2010 state-wide Washington State Healthy Youth Survey (HYS). Using a clustered sampling design, this survey is administered to students in 6th, 8th, 10th, and 12th grade classrooms on even years. Students in the older grades take a two-form “interleaved” survey with core questions and two questionnaires that are randomly distributed. The 6th grade survey consists of a single-form, shorter version with fewer questions. This study evaluates results from the 2010 HYS Form B, a form of the questionnaire that included questions on sleep and work experience. Responses are anonymous and participation is voluntary for schools and students.
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around your home, while working for pay, have you ever been injured badly enough that you needed to go to a nurse, doctor, or hospital?” Possible responses included “Never worked for pay,” “Have worked, but never been injured enough to see a nurse or doctor,” and “Yes, I was injured at work and needed to go to a nurse, doctor or hospital.” A student was considered having ever had a work-related injury if they selected the latter response. The total number of students reported having ever worked was calculated by combining the students who reported having worked but never been injured and those who reported ever being injured at work.
Independent variables School night sleep duration was self-reported and ascertained from the question in the 2010 HYS Form B, “On an average school night, how many hours do you sleep?” Average weekend night sleep duration was estimated using this following question: “On an average weekend night (Friday or Saturday), how many hours do you sleep?” Both variables were originally categorized as “5 hr or less,” “about 6 hr,” “about 7 hr,” “about 8 hr,” and “9 hr or more;” for analyses, “about 6 hr” and “about 7 hr” were combined into a single category.
Covariates Analyses included demographic information reported by students in the 2010 HYS Form B, including grade (8th [reference], 10th, 12th), age (categorized as 12 or younger, 13–15 [reference], 16–17, and 18 or older), gender (male [reference], female), race/ethnicity (non-Hispanic White [reference], non-Hispanic Black, Hispanic or Latino/a, or other/unknown/multiple), language spoken at home (English [reference], non-English), maternal education (12 or fewer years, more than 12 years [reference], missing), living situation (with parent or guardian or elsewhere [reference], which could include the following locations: friend’s house, motel/hotel, shelter, car, campground, or on their own), and student assessment of academic performance in the previous year (“Putting them all together, what were your grades like last year?”). Models also included the following potential confounders: lifetime alcohol use (“Have you ever had more than a sip or two of beer, wine, or hard liquor?”; responses were coded as yes [reference] or no, and days per week engaged in supervised after-school activities (0 days, 1–2 days, or 3 or more days [reference]).
Measures Dependent variable
Statistical Analyses
Adolescent work-related injury was assessed from the question in the 2010 HYS Form B, “NOT counting chores
Variables were described across adolescents who reported having a work-related injury and those who did
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not; bivariate comparisons were made using chi-squared tests. We used multivariable logistic regression models to evaluate the association between average sleep duration and report of ever having a work-related injury. The covariates listed above were included in all models, except for grade, which was correlated with age. We used Stata/MP v.13.0 for all analyses, including svy commands to account for the complex survey design. Because it involves analysis of de-identified data, this study was determined to be exempt from review by the Washington State Institutional Review Board.
RESULTS The 2010 HYS was completed by 22,520 students in the state-wide sample; overall response rates were 77%, 67%, and 53% for 8th, 10th, and 12th grades respectively. The HYS Form B with questions about work injury and sleep was completed by 11,222 students in 2010. A total of 4,175 (37.2%) students responding to Form B, reported having ever worked for pay outside of the home. Students with a history of working for pay more often reported fewer school and weekend night sleep hours than students with no history of working (Fig. 1, chi2 test, P < 0.01). To construct the final study sample, we excluded students who were missing data for the independent variable
describing school night sleep duration (n ¼ 31, 0.7%). The final study sample included 4,144 students in 8th (29.7%), 10th (29.2%) and 12th (41.1%) grades (Table I). Of the study sample, 6.4% (N ¼ 265) reported ever seeking treatment from a nurse, doctor, or hospital for a work-related injury. Work-related injury history varied significantly by grade, sex, age, race/ethnicity, maternal education, living situation, academic grades, and alcohol use (chi2 tests, P < 0.01). Among adolescents with a history of working, those who reported ever seeking treatment for a work-related injury indicated sleeping for 5 or fewer hours on an average school night more frequently than their working peers without a history of injury (Table II). A similar pattern was observed for average weekend night sleep duration. Multivariable logistic regression results indicate that compared to adolescents who reported sleeping about 8 hr on a school night, those who sleep 5 or fewer hours have a 1.91 times increased odds of ever having had a work-related injury for which medical treatment was sought (OR: 2.91, 95% CI: 1.85–4.57) (Table III). Those who reported sleeping about 6–7 hr on school nights also had a higher odds of reporting a history of a work-related injury compared to students who reported sleeping 8 hr, after adjusting for covariates (OR 1.52, 95:CI: 1.03–2.23). No significant association was observed between average weekend night sleep duration and the odds of ever having had a work-related injury for which medical treatment was sought (Table III).
School and Weekend Night Sleep Duration by Student Work History 60% 53%
50% 46%
Proportion of Students
43% 40%
38%
32% 30%
27% 23%
22%
21% 20%
20%
16% 11%
12%
17%
11% 9%
10%
0% 5 hr or less
About 6-7 hr
About 8 hr
9 hr or more
5 hr or less
School night
About 6-7 hr
About 8 hr
Weekend night Never worked
Ever worked
FIGURE 1. Self-reported average school and weekend night sleep duration among students who reported a history of every working for pay and students who never worked, Washington State Healthy Youth Survey, 2010.
9 hr or more
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TABLE I. Characteristics of Adolescents by Work-Related Injury History, Washington State Healthy Youth Survey, 2010 Ever sought medical treatment for a work-related injurya Characteristic
Yes (N ¼ 265)
No (N ¼ 3879)
110 (41.5) 73 (27.6) 82 (30.9)
1121 (28.9) 1137 (29.3) 1621 (41.8)
175 (66.3) 89 (33.7)
1993 (51.4) 1885 (48.6)
3 (1.1) 156 (58.9) 68 (25.7) 38 (14.3)
11 (0.3) 1878 (48.4) 1541 (39.8) 447 (11.5)
126 (51.9) 23 (9.5) 55 (22.6) 39 (16.1)
2373 (67.0) 154 (4.4) 496 (14.0) 518 (14.6)
98 (37.6) 122 (46.7) 41 (15.7)
2077 (53.9) 1287 (33.4) 491 (12.7)
200 (74.5) 65 (24.5)
3660 (94.4) 219 (5.6)
76 (29.3) 76 (29.3) 57 (22.0) 19 (7.3) 31 (12.0)
1471 (38.3) 1350 (35.1) 740 (19.3) 184 (5.8) 99 (2.6)
62 (23.6) 201 (76.4)
1339 (34.7) 2523 (65.3)
112 (42.2) 54 (20.4) 99 (37.4)
1445 (37.4) 796 (20.6) 1620 (42.0)
b
Grade 8th 10th 12th Sexb Male Female Ageb 12 or younger 13^15 years 16^17 years 18 or older Race/Ethnicityb Non-Hispanic White Non-Hispanic Black Hispanic or Latino/a Other Maternal educationb < ¼ 12 years >12 years Data missing Living situationb With parents or guardian Elsewhere Typical gradesb Mostly A’s Mostly B’s Mostly C’s Mostly D’s Mostly F’s Ever consumed alcoholb Yes No Days per week engaged in after school activities 0 days 1^2 days 3 or more days
Values indicate N (%). a Work-related injury is characterized by respondent indicating that, while working for pay (not counting chores around their home), he/she had you ever been injured badly enough that you needed to go to a nurse, doctor, or hospital. b Chi-squared test comparing distribution of students with work-related injuries across characteristics, P < 0.01.
DISCUSSION Young workers, particularly those under age 18, are at increased risk for occupational injuries compared to their adult counterparts [Institute of Medicine and National Research Council, 1998; Miller and Kaufman, 1998; Castillo
et al., 1999; Weller et al., 2003; Salminen, 2004; Windau and Meyer 2005; Zierold and Anderson, 2006; Centers for Disease Control and Prevention, 2010; Rauscher et al., 2011; Miller 2012]. This study found that among teens with a history of working, reduced sleep duration was associated with increased odds of ever having a work-related injury.
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TABLE II. Self-Reported Sleep Duration Among Adolescents With and Without a History of a Work-Related Injury, Washington State Healthy Youth Survey, 2010 Ever sought medical treatment for a work-related injurya Yes (N ¼ 265)
No (N ¼ 3879)
b
Average school night sleep duration 5 or fewer hours 64 (24.2) About 6^7 hr 128 (48.3) About 8 hr 43 (16.2) 9 or more hours 30 (11.3) Average weekend night sleep durationb 5 or fewer hours 78 (29.8) About 6^7 hr 65 (24.8) About 8 hr 52 (19.9) 9 or more hours 67 (25.6)
414 (10.7) 2063 (53.2) 1078 (27.8) 324 (8.4) 629 (16.3) 889 (23.1) 848 (22.0) 1488 (38.6)
Values indicate N (%). a Work-relatedinjuryischaracterizedbyrespondentindicatingthat,whileworkingfor pay (not counting chores around their home),he/she had you ever been injuredbadly enough that you needed to go to a nurse, doctor, or hospital. b Chi-squared test comparing distribution of students with work-related injuries across levels of sleep, P < 0.01.
Previous research supports the relationship between engagement in work and adolescent sleep patterns [Carskadon 1990; Teixeira et al., 2004; Teixeira et al., 2006; Fischer et al., 2008]. Teixeira and colleagues’ evaluation of working students in Sao Paulo, Brazil found evidence of poorer sleep quality, chronic sleep debt, shorter sleep duration, and increased sleepiness among working students, compared to their non-working peers [Teixeira et al., 2004, 2006]. Similarly, Fischer and colleagues reported that among adolescents attending evening classes, working was significantly associated with shorter sleep duration during the week, and working 8–10 hr/day was associated with longer, rebound sleep on the weekends.[Fischer et al., 2008] Although the 2010 HYS did not ask teens about working multiple jobs, Zierold and colleagues found that those working more than one job were more likely to work past 11 p.m. and work more than 40 hr per week and were 1.6 times more likely to be injured at work [Zierold et al., 2011]. While the injury finding in Zierold et al., 2011 was not statistically significant, the possibility of working more than one job should not be excluded as a contributing factor in our results. In addition, although this study did not ask about youth working in their family’s business, previous research suggests that those working in their family’s business reported performed more hazardous work and suffered more severe injuries than teens working for other employers [Zierold et al., 2012]. While this study found a significant relationship between school night sleep duration and work-related injury
history, no relationship with weekend sleep duration was identified. It is not unusual for adolescents to report shorter sleep durations during school nights compared to weekends [Wolfson and Carskadon, 1998; Crowley and Carskadon, 2010] and it has been suggested that adolescents may sleep longer on weekends in order to compensate for insufficient sleep during the week [Fischer et al., 2008; Liu et al., 2008]. Such weekend “catch-up” sleep may reflect actual sleep needs of adolescents. Insufficient school night sleep and weekend bedtime delays are associated with daytime sleepiness and changes in function, including depressive mood and risk-taking behavior [Wolfson and Carskadon, 1998; O’Brien and Mindell, 2005]. While we were not able to assess weekend sleep schedule delays in this study, it may be possible that the relationship between weekday and weekend sleep duration could contribute to occupational injury among working teens. Many have pointed toward the injury risks associated with sleep deprivation in this population, however, to our knowledge, this is the first study to examine this relationship in adolescents. In adults, poor sleep quality, sleep problems, reduced sleep duration, and early waking hours are known risk factors for occupational injuries [Uehli et al., 2013, 2014; Chiu et al., 2014]. A recent literature review concluded that among workers aged 16–70 years, approximately 13% of work-related injuries could be attributed to sleep problems [Uehli et al., 2014]. In adolescents, however, the relationship between sleep problems and work-related injuries has thus far been inadequately explored. This study contributes to the literature by describing the potential impact of school night and weekend sleep duration on injury risk in teens. An ancillary finding of this study may warrant future investigation. Compared to older students, a higher proportion of 8th grade students reported ever having a work-related injury (Table I). This finding is alarming, given that most 8th graders would typically be below the legal age of work and their lifetime exposure to work should be less than older students. This study has several limitations. First, the reported occupational injuries among the surveyed adolescents were relatively infrequent. Accordingly, the HYS asked students to report their lifetime (“ever”) work-related injury experience. Sleep duration is reported contemporaneously. This study assumes that average sleep duration does not change over time. Given the cross-sectional nature of this study, it is only feasible to evaluate the association between sleep duration and occupational injury, not causation. It is possible that an occupational injury, such as a head injury or other injury resulting in pain or disability, could impact sleep [Kaufman et al., 2001; Pillar et al., 2003]; however, we were not able to investigate the potential directionality of the association. Second, in addition to sleep duration, sleep quality has been associated with poorer health and
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TABLE III. Association Between Self-Reported Average School and Weekend Night Sleep Duration and History of a Work-Related Injury, Washington State Healthy Youth Survey, 2010
Average school night sleep duration 5 or fewer hours About 6^7 hr About 8 hr 9 or more hours Average weekend night sleep duration 5 or fewer hours About 6^7 hr About 8 hr 9 or more hours Sex Male Female Age 12 or younger 13^15 years 16^17 years 18 or older Race/Ethnicity Non-Hispanic White Non-Hispanic Black Hispanic or Latino/a Other Maternal education < ¼ 12 years >12 years Data missing Living situation With parents or guardian Elsewhere Typical grades Mostly A’s Mostly B’s Mostly C’s Mostly D’s Mostly F’s Ever consumed alcohol Yes No Days per week engaged in after school activities 0 days 1^2 days 3 or more days
Adjusted OR (95% CI)
Adjusted OR (95% CI)
2.91 (1.85^4.57) 1.52 (1.03^2.23) Reference 1.60 (0.96^2.64)
ç ç ç ç
ç ç ç ç
1.19 (0.75^1.88) 0.95 (0.63^1.43) Reference 0.64 (0.42^1.00)
Reference 0.53 (0.38^0.74)
Reference 0.55 (0.40^0.77)
1.93 (0.40^9.29) Reference 0.56 (0.40^0.78) 0.91 (0.58^1.43)
2.32 (0.54^10.00) Reference 0.61 (0.44^0.84) 0.96 (0.63^1.48)
Reference 1.44 (0.82^2.53) 1.60 (1.09^2.33) 1.07 (0.72^1.60)
Reference 1.46 (0.81^2.61) 1.51 (1.03^2.22) 1.07 (0.71^1.60)
Reference 1.41 (1.05^1.90) 1.19 (0.76^1.86)
Reference 1.44 (1.07^1.93) 1.22 (0.77^1.91)
Reference 3.63 (2.46^5.34)
Reference 3.77 (2.56^5.54)
Reference 0.86 (0.63^1.18) 1.01 (0.67^1.53) 0.91 (0.52^1.59) 1.85 (1.01^3.39)
Reference 0.83 (0.60^1.14) 0.98 (0.65^1.49) 1.00 (0.60^1.69) 1.95 (1.04^3.67)
Reference 1.56 (1.11^2.21)
Reference 1.55 (0.59^1.13)
0.81 (0.59^1.12) 0.76 (0.48^1.19) Reference
0.81 (0.59^1.13) 0.78 (0.50^1.22) Reference
CI, confidence interval; OR, odds ratio. OR estimates were adjusted for age sex race/ethnicity maternal education living situation typical grades lifetime alcohol use and after school activities.
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academic outcomes in adolescents [Javaheri et al., 2008; Short et al., 2013] and possibly occupational injury in adults [Uehli et al., 2013]. Sleep quality was not ascertained in the HYS and therefore we cannot measure that impact in this study, however we acknowledge it may also be a contributing factor to negative impacts found in other studies. Similarly, we do not have data regarding fatigue or exhaustion, both of which can influence workrelated injury risk. The 2010 HYS did not ask students the type of job in which they were engaged when they were injured, or did it include questions on work hours or work in multiple jobs. These factors are critical and should be considered in future surveys. Finally, data gathered in any survey study, such as this one, are self-reported by the teens and not validated by another method. The anonymous and voluntary nature of the survey reduce the likelihood of fabricated or falsified responses, however, it does not preclude social desirability bias [Groves et al., 2009]. It is unlikely, however, that these effects would substantially impact the results of this study [Fan et al., 2006]. Working adolescents experience the benefits of the working world, including the opportunity to earn an income and learn skills necessary for positive career development. However, there are hazards and risks associated with work, particularly for teens. Young workers also experience deleterious outcomes of work, both directly, such as injuries [Centers for Disease Control and Prevention, 2010] and workplace violence [Rauscher, 2008], and indirectly, such as increased substance use, poor school performance [Warren and Lee, 2003; Staff et al., 2010; Osilla et al., 2013], and decreased sleep duration, as our data show. This research suggests that reduced sleep duration may be associated with work-related injuries among working teens. It is crucial to consider not only the injury risks, but also the health, well-being, and psychosocial impacts associated with adolescent work. Work schedules for youth must be kept in balance with their developmental needs and other equally important ageappropriate activities. Additional research to better understand the influence of long work hours and late night work schedules on these outcomes among adolescents is warranted. Also, existing child labor regulations that limit work hours for youth must be followed and policies should be developed to address the gaps that currently exist.
ACKNOWLEDGMENTS Authors would like to thank Lillian S. Bensley, PhD, MS at the Washington State Department of Health for her assistance in obtaining and understanding the HYS dataset. Authors have no conflicts of interest to declare, including relevant financial interests, activities, relationships, and affiliations.
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Disclosure Statement: The authors report no conflicts of interests.
