Getting up earlier on work days may harm metabolic health, according to researchers.
Published in the Journal of Clinical Endocrinology & Metabolism, the study found that routine sleep changes - such as waking up early on weekdays - may increase the risk for metabolic conditions, such as obesity, diabetes and heart disease.
Previous research has already established that sleep disruption can pose negative health implications. For example, a study reported by Medical News Today earlier this year found that shift workers - whose circadian rhythms are frequently disrupted due to irregular working hours - are at greater risk for poor metabolic health.
However, the team involved in this latest research - including Patricia M. Wong of the University of Pittsburgh, PA - says their study is the first to show that even minor disruptions to sleep schedules among healthy, working adults can harm metabolic health.
Greater social jet lag linked to poorer metabolic health
To reach their findings, Wong and colleagues analyzed data of 447 adults aged 30-54 who were part of the Adult Health and Behavior Project Phase 2 Study. Participants worked a minimum of 25 hours weekly outside of their home.
- A 2011 sleep survey found that 43% of American adults rarely or never get a good night's sleep on weeknights
- Around 95% of those surveyed reported using some form of electronic device - such as a computer or cell phone - before bed, which can disrupt sleep
- Around 8 in 10 Americans who are getting inadequate sleep say it affects their mood.
Subjects were required to wear a wristband that measured their sleep activity and movement 24 hours a day for 1 week. They also completed a questionnaire detailing their diet and exercise habits.
Almost 85% of the participants had a later halfway point in the sleep cycle - known as mid-sleep - on non-working days than on working days, according to the researchers, indicating that these subjects awoke later on non-working days.
The researchers found that subjects who had a greater shift between their sleep schedules on working and non-working days - known as "social jet lag" - were more likely to have poor cholesterol levels, larger waist circumference, higher body mass index (BMI), higher fasting insulin levels and greater insulin resistance, compared with those who had less social jet lag.
"These metabolic changes can contribute to the development of obesity, diabetes and cardiovascular disease," notes Wong.
The team says their results remained even after accounting for participants' diet, physical activity and other sleep behaviors.
Commenting on the possible implications of their findings, Wong says:
"If future studies replicate what we found here, then we may need to consider as a society how modern work and social obligations are affecting our sleep and health.
There could be benefits to clinical interventions focused on circadian disturbances, workplace education to help employees and their families make informed decisions about structuring their schedules, and policies to encourage employers to consider these issues."