Job Demands
All variables were measured consistently at T1 and T2. Job demands were captured by perceived unfairness and discrimination. Job resources were captured by coworker and supervisor support.
Perceived Unfairness. Participants rated the level of perceived unfairness about work using a 6-item scale (Ryff et al., 2003). The items read: “(1) I feel cheated about the chances I have had to work at good jobs, (2) When I think about the work I do on my job, I feel a good deal of pride, (3) I feel that others respect the work I do on my job, (4) Most people have more rewarding jobs than I do, (5) When it comes to my work life, I’ve had opportunities that are as good as most people’s (reverse coded), and (6) It makes me discouraged that other people have much better jobs that I do.” Responses options were 1 (A lot), 2 (Some), 3 (A little), and 4 (Not at all). The response scale and certain items were reverse coded, so higher values indicated more perceived unfairness. Cronbach’s alpha was .75 at T1 and .75 at T2.
Job Discrimination. Participants rated the level of perceived job discrimination at work based on a 6-item scale (Brim et al., 2004). The items read: “(1) How often do you think you are unfairly given the jobs that no one else wanted to do?, (2) How often are you watched more closely than other workers?, (3) How often does your supervisor or boss use ethnic, racial, or sexual slurs or jokes?, (4) How often do your coworkers use ethnic, racial, or sexual slurs or jokes?, (5) How often do you feel that you are ignored or not taken seriously by your boss?, (6) How often has a coworker with less experience and qualifications gotten promoted before you?” (Ryff et al., 2004). Response options were 1 (Never), 2 (Less than once a year), 3 (A few times a year), 4 (A few times a month), and 5 (Once a week or more). Higher values indicated more job discrimination. Cronbach’s alpha was .78 at T1 and .79 at T2.
Coworker Support. Participants rated the level of coworker support at work based on a 2-item scale previously used in other studies (Ettner & Grzywacz, 2001; Grzywacz & Marks, 2000). The items read: “(1) How often do you get help and support from your coworkers? and (2) How often are your coworkers willing to listen to your work-related problems?” (Brim et al., 2004). Each question was coded as 1 (All of the time), 2 (Most of the time), 3 (Sometimes), 4 (Rarely), and 5 (Never). All items were reverse-coded, so that higher values indicated more coworker support. Cronbach’s alpha was .67 at T1 and .72 at T2.
Supervisor Support. Participants rated the level of supervisor support at work based on a 3-item scale previously used (Ettner & Grzywacz, 2001; Grzywacz & Marks, 2000). The items read: “(1) How often do you get the information you need from your supervisor or superiors?”, (2) “How often do you get help and support from your immediate supervisor?”, (3) “How often is your immediate supervisor willing to listen to your work-related problems?” Each question was coded as 1 (All of the time), 2 (Most of the time), 3 (Sometimes), 4 (Rarely), and 5 (Never). All items were reverse-coded, so that higher values indicated more supervisor support. Cronbach’s alpha was .87 at T1 and .87 at T2.
Negative Spillover. Participants rated the level of negative spillover using a 4-item scale (Grzywacz, 2000; Grzywacz & Marks, 2000). The items read: “(1) Your job reduces the effort you can give to activities at home, (2) Stress at work makes you irritable at home, (3) Your job makes you feel too tired to do the things that need attention at home, (4) Job worries or problems distract you when you are at home.” Each question was coded as 1 (All of the time), 2 (Most of the time), 3 (Sometimes), 4 (Rarely), and 5 (Never). All items were reverse-coded, so higher values indicated a higher level of negative spillover. Cronbach’s alpha was .82 at T1 and .85 at T2.
Positive Spillover. positive spillover was assessed using a 4-item scale (Grzywacz, 2000; Grzywacz & Marks, 2000). The items read: “(1) The things you do at work help you deal with personal and practical issues at home?, (2) The things you do at work make you a more interesting person at home, (3) Having a good day on your job makes you a better companion when you get home, and (4) The skills you use on your job are useful for things you have to do at home.” Each question was coded as 1 (All of the time), 2 (Most of the time), 3 (Sometimes), 4 (Rarely), and 5 (Never). All items were reverse-coded, so higher values indicated a higher level of positive spillover. Cronbach’s alpha was .72 at T1 and .73 at T2.
Sleep Health Problems. Sleep health problems were captured in two ways: (1) using individual dimension scores and (2) using a composite of 5 dimensions in Buysse’s (2014) Ru-SATED model. The model captured sleep irregularity, dissatisfaction, nap frequency (alertness), inefficiency, and suboptimal sleep duration, but could not capture timing because this information was not available in the MIDUS survey data. We created binary variables for each sleep dimension following cut-off points used in the previous literature (Lee et al., 2022; Smith et al., 2023), such that 0 represents good sleep and 1 represents poor sleep or a sleep problem.
Irregularity was defined as the absolute value difference in sleep duration between workdays and nonwork days. Irregularity was expressed as a binary variable where the absolute value difference of more than 60 minutes was coded as 1 and 60 minutes or less was coded as 0. Dissatisfaction was assessed by 4 insomnia symptoms following previous literature (Lee et al., 2022; Knutson et al., 2017): (1) Having trouble falling asleep, (2) waking up during the night, and having trouble falling back to sleep, (3) waking up early in the morning, and having trouble falling back to sleep, and (4) feeling unrested throughout the daily regardless of the duration of last night’s sleep. Respondents answered each item as either 1 (sometimes, often, or almost always) or 0 (rarely or never) on each item. The dissatisfaction variable was dichotomized by assigning 0 to responses with “Rarely or Never” on all 4 items and assigning 1 to responses with at least one “Sometimes, Often, or Almost Always'' response to 1 of the 4 items. Nap frequency (lack of alertness) was operationalized as the number of times one napped for 5 minutes or more during the week. Nap frequency was expressed as a binary variable where more than 2 naps a week was coded as 1 and 2 naps or less a week was coded as 0. MIDUS does not capture sleep timing, so this dimension of Ru-SATED was excluded. Inefficiency was defined as how long it took the respondent to fall asleep. Inefficiency was measured by sleep onset latency. We created a binary indicator with 1 equal to respondents taking more than 30 minutes to fall asleep, and 0 equal to respondents taking 30 minutes or less to fall asleep. Lastly, suboptimal sleep duration was captured by the average amount of sleep the participant received on workdays. Average sleep durations that were less than 6 hours or greater than 8 hours were coded as 1 and reported sleep between 6 to 8 hours was coded as 0. To create the composite score, all binary indicators were summed such that possible scores ranged from 0 to 5, with higher scores representing more sleep health problems.
Covariates
Fully adjusted models controlled for potentially confounding variables, which have been shown to be associated with sleep and work characteristics (Adults et al., 2012; Grandner et al., 2010). Covariates were age (in years), sex (1 = Men, 0 = Women), race (0 = Non-Hispanic White, 1 = Hispanic Whites/Person of color), education (1 = no school/some grade school to 12 = professional degrees such as Ph.D., ED.D., or MD), partnered status (0 = partnered including married and cohabitating, 1 = single including un married, separated, and divorced), the number of children living in the household, self-rated physical health (1 = Poor to 5 = Excellent), and average amount of work hours per week. We also controlled for neuroticism (1 = Less neurotic to 4 = More neurotic), as it is a known predictor of poor sleep health and may influence the perception and response to questions on workplace experiences and spillover (Duggan et al., 2014; Widiger & Oltmanns, 2017). All continuous variables were centered at the sample means. For the longitudinal analyses, all covariates, except race and sex, were measured at T2. Following Lee and colleagues (2019), we controlled for changes in partnered status over time; 4 categories were created so that those who were continuously partnered (married/cohabitating at both T1 and T2) were coded 1, single to partnered (e.g., unmarried at T1 and married at T2) were coded 2, single throughout (e.g., unmarried at both T1 and T2) were coded 3, or other change patterns (e.g., married at T1 and divorced at T2) were coded 4.
Statistical Analyses
We tested the study hypotheses cross-sectionally and prospectively. The cross-sectional analyses used data from T1, and prospective analyses used work characteristics and spillover from T1 and sleep health from T2 (see Fig. 1). For both approaches, analyses were conducted separately for each work characteristic and for positive spillover or negative spillover. Fully adjusted general linear models were first used to examine individual paths (a, b, c, and c’). Indirect effect tests were tested using PROCESS Macro (Hayes, 2017; Preacher & Hayes, 2004). All analyses were conducted in SAS v9.4 (SAS Institute, Cary NC). Statistical significance was determined if the 95% confidence interval did not include 0.
Supplemental analyses were conducted to examine 1) the cross-sectional associations between work characteristics and individual sleep dimensions, and 2) change score analyses with work characteristics from T1, the change in spillover from T1 to T2, and sleep health at T2. To test the individual sleep dimensions, we examined the continuous variables for sleep irregularity (absolute value of the difference between workday and non-workday sleep), sleep dissatisfaction (count variable of number of insomnia symptoms, Range = 0–4), average nap frequency over the week (Range = 0–12), sleep latency (time in decimal hours), and average sleep duration (time in decimal hours).