'Social jetlag' may up heart disease, diabetes risk

Routine sleep changes such as waking up early for work during the week may raise the risk of developing metabolic problems such as diabetes and heart disease, according to a new study.
Researchers have long recognised that shift work can contribute to metabolic risk because of the continual disruption to the circadian system.
Shift workers are more likely to develop metabolic syndrome, coronary heart disease and type 2 diabetes than employees with regular daytime shifts.
Sleep disruption is among the factors that have contributed to rising rates of diabetes and obesity.
"Social jetlag refers to the mismatch between an individual's biological circadian rhythm and their socially imposed sleep schedules," said Patricia M Wong, of the University of Pittsburgh in US.

This is the first study to show that even among healthy, working adults who experience a less extreme range of mismatches in their sleep schedule, social jetlag can contribute to metabolic problems, said Wong.

"These metabolic changes can contribute to the development of obesity, diabetes and cardiovascular disease," she said.
Researchers examined sleep patterns and cardiometabolic risk in a group of 447 men and women who took part in the Adult Health and Behaviour Project Phase 2 study in US.
The participants were between the ages of 30 and 54, and they worked at least 25 hours a week outside the home.

They wore a wristband that measured their movement and sleep 24 hours a day for a week. The researchers used questionnaires to assess the participants' diet and exercise habits.
Among the participants, nearly 85 per cent had a later halfway point in their sleep cycle - a measurement known as midsleep - on free days compared to work days.
The other 15 per cent had an earlier midsleep on free days than on work days.
Participants who had a greater misalignment between their sleep schedules on free and work days tended to have poorer cholesterol profiles, higher fasting insulin levels, larger waist circumference, higher body-mass index and were more resistant to insulin than those who had less social jetlag.

The association persisted even when the researchers adjusted the measurements to account for variation in other sleep measures and health behaviours such as physical activity and calorie intake.
The study was published in the Journal of Clinical Endocrinology and Metabolism.