Much as jetting across time zones can force a person to wake-up, eat and work at times that conflict with their body’s idea of what time it is, so-called social jet lag happens when social pressures like work or school cause people to be active at times that conflict with their natural internal clock.
In the study, researchers measured social jet lag by tracking the degree to which people followed one sleep schedule on work days and another on days off.
The study team found that diabetics who had social jet lag of more than 90 minutes tended to have higher blood sugar than their counterparts who didn’t experience as much variation in their bedtimes and wake-up times on work days and non-work days.
“A general piece of advice, not only for patients with diabetes but for everyone, is to try to live our lives in harmony with our circadian clock as much as possible,” said Andrew Coogan, senior author of the study and a researcher at the National University of Ireland, Maynooth.
“Unfortunately, for many this is very difficult,” Coogan said. “If we have to be at work for 8:30 am and have an hour commute, then we simply have to get up at 7 am, although at the weekend we might not wake until after 9 am.”
Some previous research has linked what’s known as an evening chronotype – or a preference for being awake later at night – with an increased risk of poor blood sugar control with diabetes, researchers note in Sleep Medicine.
All of the patients in the current study had type 2 diabetes, which is associated with obesity and aging and happens when the body can’t properly use or make enough of the hormone insulin to convert blood sugar into energy.
Almost two-thirds of the patients were obese, and one in four were had severe obesity.
Half of them had lived with diabetes for at least seven years.
At the start of the study, many of the participants had poorly controlled diabetes, based on blood tests that show the percentage of haemoglobin (a molecule on red blood cells) that is coated with sugar.
These so-called haemoglobin A1c levels reflect average blood sugar levels over about three months. Readings above 6.5 signal diabetes, and half of the patients in the study had readings of at least 6.9, which is considered poorly controlled blood sugar.
Although higher degrees of social jetlag, or circadian misalignment, were linked to poor blood sugar control, chronotype didn’t appear to directly impact blood sugar levels.
“Our findings suggest that this misalignment between our circadian clocks and our social schedule might be associated with more severe disease in patients with type 2 diabetes,” Coogan said.
The study wasn’t designed to prove whether or how sleep schedules or divergence from natural circadian rhythms might directly impact blood sugar in people with diabetes.
“We do not understand how this discrepancy between biological and societal time results in the adverse effects it is associated with, but suspect that the tension of social jetlag somehow weakens the circadian system,” Coogan said.