BOSTON — If you’re a weekday early riser, sleeping in on weekends could be hazardous to your health, researchers reported here.
Going to bed and waking up later on weekends than weekdays — the common sleep pattern recently dubbed social jet lag — was associated with a host of poor health outcomes, including chronic fatigue, poor mood and even an increased risk for heart disease in a preliminary analysis reported this week at SLEEP 2017, the joint annual meeting of the American Society of Sleep Medicine and the Sleep Research Society.
Sleeping in on weekends is a luxury that seemingly would translate to a net positive for health, rather than a negative. But Sierra B. Forbush, of the University of Arizona in Tucson, said the disruption to the body’s circadian clock caused by late-night bedtimes followed by later weekend wake times appears to be an independent risk factor for poorer health.
“These results indicate that sleep regularity, beyond sleep duration alone, may play a significant role in overall health,” she told MedPage Today, adding that keeping a regular sleep schedule throughout the week may prove to be an effective intervention for reducing cardiovascular risk and the risk of other health problems.
The misalignment of biological and social time that defines social jet lag has been suggested in earlier studies to be associated with a higher risk for substance use, especially smoking, and for obesity. But Forbush said the previous research on social jet lag has typically not controlled for shorter overall sleep and insomnia.
“Social jet lag … is caused by social responsibility,” Forbush said. “That could be your school or your work. Many people on weekdays wake up at, say, 7 a.m. to get to work by 8, but on the weekends they want to sleep in. We looked at how that shift affects your health.
Forbush and colleagues analyzed data from the NIH-funded Sleep and Healthy Activity, Diet, Environment, and Socialization (SHADES) study, which is a community-based survey of close to 1,000 adults ages 22-60, conducted by the University of Pennsylvania Center for Sleep & Circadian Neurobiology.
Social jet lag, represented in hours, was assessed using the Sleep Timing Questionnaire and calculated by subtracting weekday from weekend sleep midpoint.
A total of 984 study participants provided complete data, and insomnia. Covariates included age, sex, race/ethnicity, education, employment, income, sleep duration, and insomnia measured with the Insomnia Severity Index (ISI).
Overall health was self-reported as “excellent,” “good,” or “fair/poor.” Cardiovascular disease was assessed as history of any condition. Depression was measured with the Patient Health Questionnaire (PHQ), fatigue with the Fatigue Severity Scale (FSS), and sleepiness with the Epworth Sleepiness Scale (ESS).
Regression modeling, adjusted for all covariates, was used to examine whether social jet lag predicted any of these outcomes.
Greater social jet lag was seen among high-school graduates versus college graduates, and social jet lag was less common among African Americans, unemployed people, and those with lower incomes (compared to those with higher incomes).
Adjusted for covariates, each hour of social jet lag was associated with a 22.1% and 28.3% increased likelihood of good and fair/poor health, respectively (versus excellent health) (P<0.01).
Each hour was associated with an 11.1% increased likelihood of heart disease (P<0.05). Additionally, each hour was associated with 0.25 PHQ points, 0.19 ESS points, and 0.56 FSS points (P<0.05).
The researchers concluded that — in this community sample and after adjusting for race/ethnicity, income, education, employment, sleep duration, and insomnia — social jet lag was associated with poorer health, heart disease, worse mood, and increased sleepiness and fatigue.
With every hour of social jet lag respondents were 22% more likely to report that their overall health was “good” instead of “excellent” and 28% more likely to say their health was “fair or poor” instead of “excellent.”
“There are a lot different health outcomes that appear to be affected by shifting sleep, but we don’t fully understand [the reasons] for this,” said Forbush, an undergraduate research assistant at the University of Arizona Sleep and Health Research Program. Michael A Grandner, PhD, who directs the program, was senior author of the study.