Preliminary results of a new study show that social jet lag has emerged as an important circadian marker for health outcomes.

Results show that social jet lag, which occurs when you go to bed and wake up later on weekends than during the week, is associated with poorer health, worse mood, and increased sleepiness and fatigue. Each hour of social jet lag also is associated with an 11-percent increase in the likelihood of heart disease. These effects are independent of sleep duration and insomnia symptoms, which are related to both social jet lag and health.

"These results indicate that sleep regularity, beyond sleep duration alone, plays a significant role in our health," said lead author Sierra B. Forbush, an undergraduate research assistant in the Sleep and Health Research Program at the University of Arizona in Tucson. "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."

The research team was led by senior author Michael A. Grandner, PhD, MTR, director of the Sleep and Health Research Program. They utilized data from the community-based Sleep and Healthy Activity, Diet, Environment, and Socialization (SHADES) study, analyzing survey responses from 984 adults between the ages of 22 and 60 years.

Social jet lag was assessed using the Sleep Timing Questionnaire and was calculated by subtracting weekday from weekend sleep midpoint. Overall health was self-reported using a standardized scale, and survey questions also assessed sleep duration, insomnia, cardiovascular disease, fatigue, and sleepiness.

The American Academy of Sleep Medicine recommends that adults should sleep 7 or more hours per night on a regular basis to promote optimal health. In addition to adequate duration, healthy sleep requires good quality, appropriate timing and regularity.