“Social jet lag,” the time difference experienced between sleep patterns on days off compared to work days, may have a negative impact on health, a new study suggests.
Sleep and wakefulness disorders affect an estimated 15 to 20 percent of US adults, who in turn are more likely to suffer from chronic disorders, such as depression, substance abuse, hypertension, diabetes, cancer, stroke, and all-cause mortality, according to the US Department of Health and Human Services.
The study was led by Sierra B. Forbush, a research assistant in the Sleep and Health Research Program at the University of Arizona, who completed the research with Michael A. Grandner, head of the program. Here, Forbush speaks about her research on social jet lag and sleep:
What is social jet lag and how does it relate to sleep?
Social jet lag occurs when there is a discrepancy between your body’s internal clock and your sleep schedule, exemplified by sleeping shorter times during the week and sleeping longer but staying up later during the weekend.
By measuring social jet lag, we found that sleep regularity, beyond sleep duration alone, plays a significant role in our health. This suggests that a regular sleep schedule may be an effective, relatively simple, and inexpensive preventative treatment for heart disease, as well as many other health problems.
What surprised you most about your findings and why are these results important?
The most surprising findings of the study were that each hour of social jet lag was associated with quite a pronounced increased likelihood of good and fair/poor health rather than excellent health (22.1 percent and 28.3 percent, respectively) and, more specifically, 11.1 percent increased likelihood of heart disease. Social jet lag also was associated with poorer health, worse mood, and increased sleepiness and fatigue.
It was particularly surprising that these effects were independent of age, socioeconomic status, how much sleep people got and insomnia symptoms.
How did you come about the findings?
[Michael] Grandner was the principal investigator for the community-based sleep survey known as the SHADES study (Sleep and Health Activity, Diet, Environment and Socialization), conducted in Philadelphia at the University of Pennsylvania. I analyzed the sleep responses provided by 984 adults, ages 22 to 60, from the SHADES study.
The SHADES study was funded by the National Institutes of Health to gain better understanding about sleep as it relates to health, behavior, and the physical environment, including poverty rates, crime statistics, noise, and traffic.
Social jet lag was calculated by subtracting the weekday and weekend sleep midpoint using the SHADES study Sleep Timing Questionnaire. Overall health was self-reported using a standardized scale with survey questions on sleep duration, insomnia, cardiovascular disease, fatigue, and sleepiness.
You are an undergraduate student and this research has resonated nationally. How did you become involved in sleep research and the study?
My interest in studying sleep and health came from my personal experience with headaches. As a freshman at the University of Arizona, I regularly slept in on the weekends and was forced to wake up early on Monday mornings to attend a science lab at 8 am. I consistently had migraines when Monday evening rolled around.
My first year working in Dr. Grandner’s Sleep and Health Research Program, I completed a study looking more specifically at headaches (Longitudinal Co-Occurance of Headaches and Trouble Sleeping: Data From the Kansas State Employee Wellness Program) and my project on social jet lag was an idea that I brought to Dr. Grandner to be used for my honors thesis.
It’s incredible that my work as an undergraduate student has found its way onto the computer screens and radios of people internationally.