Persistence of social jetlag and sleep disruption in healthy young adults

ABSTRACT

Sleep disruption has been associated with increased risks for several major chronic diseases that develop over decades. Differences in sleep/wake timing between work and free days can result in the development of social jetlag (SJL), a chronic misalignment between a person’s preferred sleep/wake schedule and sleep/wake timing imposed by his/her work schedule. Only a few studies have examined the persistence of SJL or sleep disruption over time. This prospective investigation examined SJL and sleep characteristics over a 2-year period to evaluate whether SJL or poor sleep were chronic conditions during the study period. SJL and sleep measures (total sleep time [TST], sleep onset latency [SOL], wake after sleep onset [WASO]), and sleep efficiency [SE]), were derived from armband monitoring among 390 healthy men and women 21–35 years old. Participants wore the armband for periods of 4–10 days at 6-month intervals during the follow-up period (N = 1431 repeated observations).

The consistency of SJL or sleep disruption over time was analyzed using generalized linear mixed models (GLMMs) for repeated measures. Repeated measures latent class analysis (RMLCA) was then used to identify subgroups among the study participants with different sleep trajectories over time. Individuals in each latent group were compared using GLMMs to identify personal characteristics that differed among the latent groups.

Minor changes in mean SJL, chronotype, or TST were observed over time, whereas no statistically significant changes in SOL, WASO, or SE were observed during the study period. The RMLCA identified two groups of SJL that remained consistent throughout the study (low SJL, mean ± SE: 0.4 ± 0.04 h, 42% of the study population; and high SJL, 1.4 ± 0.03 h, 58%). Those in the SJL group with higher values tended to be employed and have an evening chronotype.

Similarly, two distinct subgroups were observed for SOL, WASO, and SE; one group with a pattern suggesting disrupted sleep over time, and another with a consistently normal sleep pattern. Analyses of TST identified three latent groups with relatively short (5.6 ± 1.0 h, 21%), intermediate (6.5 ± 1.0 h, 44%), and long (7.3 ± 1.0 h, 36%) sleep durations, all with temporally stable, linear trajectories. The results from this study suggest that sleep disturbances among young adults can persist over a 2 year period. Latent groups with poor sleep tended to be male, African American, lower income, and have an evening chronotype relative to those with more normal sleep characteristics. Characterizing the persistence of sleep disruption over time and its contributing factors could be important for understanding the role of poor sleep as a chronic disease risk factor.

KEYWORDS:

• Actigraphy
• chronotype
• social jetlag
• repeated measures latent class analysis

Acknowledgments

The authors wish to thank the study participants and the Energy Balance Study team.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Funding

J.B.B. was supported by a Dept. of Veterans Affairs Office of Research and Development grant (Merit Award: I01BX007080). J.R.H. was supported by an Established Investigator Award in Cancer Prevention and Control from the Cancer Training Branch of the National Cancer Institute (K05 CA136975). M.D.W. and J.R.H. were supported by grant number R44DK103377 [N. Shivappa and M.D.W., multiple PIs] from the National Institute of Diabetes and Digestive and Kidney Diseases. S.D.Y. was supported by an NIH grant (R01HL095799). S.N.B. has served on the scientific advisory boards of Technogym, Clarity, and Santech. He has received research funding from BodyMedia, Technogym, the U.S. Department of Defense, and the NIH; and he receives book royalties from Human Kinetics. The Energy Balance study was funded by an unrestricted grant from Coca-Cola Company. Coca-Cola representatives did not participate in the development of study protocol, data analyses, interpretation of the results, or manuscript preparation.

Additional information

Funding

J.B.B. was supported by a Dept. of Veterans Affairs Office of Research and Development grant (Merit Award: I01BX007080). J.R.H. was supported by an Established Investigator Award in Cancer Prevention and Control from the Cancer Training Branch of the National Cancer Institute (K05 CA136975). M.D.W. and J.R.H. were supported by grant number R44DK103377 [N. Shivappa and M.D.W., multiple PIs] from the National Institute of Diabetes and Digestive and Kidney Diseases. S.D.Y. was supported by an NIH grant (R01HL095799). S.N.B. has served on the scientific advisory boards of Technogym, Clarity, and Santech. He has received research funding from BodyMedia, Technogym, the U.S. Department of Defense, and the NIH; and he receives book royalties from Human Kinetics. The Energy Balance study was funded by an unrestricted grant from Coca-Cola Company. Coca-Cola representatives did not participate in the development of study protocol, data analyses, interpretation of the results, or manuscript preparation.