Four Questions: How 'Social Jet Lag' Impacts Health
A UA-led study shows that people who go to bed and wake up later on weekends than they do on weekdays may be harming their health. Lead researcher Sierra Forbush discusses her findings.

By Rebecca Ruiz Hudman, UA Health Sciences
June 21, 2017

Can't sleep? For many Americans, it's a question that comes up night after night.

A team of University of Arizona researchers is working to better understand sleep and its relationship to health. Sleep and wakefulness disorders affect an estimated 15 to 20 percent of U.S. 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 U.S. Department of Health and Human Services.

To better understand sleep, UA experts are conducting research, leading clinical trials and working as interprofessional teams to assess how sleep affects memory, mental health, stress, alertness and decision-making — and how environmental factors affect sleep.

A new UA study on "social jet lag," or the time difference experienced between sleep patterns on days off compared to work days, has emerged as an important marker for health.

The study was led by Sierra B. Forbush, a research assistant in the Sleep and Health Research Program, who in May graduated from the UA Honors College with an undergraduate degree in physiology. She completed the research under the direction of Dr. Michael A. Grandner, head of the Sleep and Health Research Program. He also is assistant professor of psychiatry, psychology and medicine at the UA.

Forbush presented the findings at the annual meeting of the Associated Professional Sleep Societies, held June 3-7 in Boston. The meeting is a joint venture of the American Academy of Sleep and the Sleep Research Society, and the research abstract was published recently in an online supplement of the journal Sleep.

Q: What is social jet lag and how does it relate to sleep?

A: 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.

Q: What surprised you most about your findings and why are these results important?

A: 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.

Q: How did you come about the findings?

A: Dr. 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.  

Q: You are an undergraduate student and this research has resonated nationally. How did you become involved in UA sleep research and the study?

A: My interest in studying sleep and health came from my personal experience with headaches. As a freshman at the UA, I regularly slept in on the weekends and was forced to wake up early on Monday mornings to attend a science lab at 8 a.m. 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.