Study links erratic sleep schedule to metabolic disorders, cardiovascular disease

Deregulation of our circadian rhythms and our sleeping-waking schedules between the week and the weekend could lead to diabetes and cardiovascular disease. (racorn/shutterstock.com)

If possible, it is better to go to bed and get up at the same time during the week and at the weekend, says a new US study which has established a link between changes to sleeping schedules and metabolic disorders.

Difficulty in waking up on Monday morning could mean we are storing up trouble in terms of metabolic disorders and cardiovascular disease.

Scientific research has already demonstrated that shift work increases the risk of metabolic disorders. The reason is thought to be the deregulation of our internal circadian clock which drives biological rhythms over a 24-hour day-night cycle and is followed by humans and animals.

Sleep disturbance is one of the factors behind the increase in metabolic disorders such as diabetes and obesity, even in people without health problems, says this study published on November 18 in The Journal of Clinical & Endocrinology Metabolism.

A team of researchers from the University of Pittsburgh in Pennsylvania in the US analyzed the sleep schedule and the cardio-metabolic risk of 447 men and women, who were participants in phase 2 of the Adult Health and Behavior Project study.

They were aged between 20 and 54, worked at least 25 hours per week and wore wristbands measuring their movement and sleep 24 hours a day for a week. The volunteers also filled in questionnaires informing the researchers about their dietary habits and physical activity.

The team noted that almost 85 per cent of the participants had a lag in their sleep cycles, waking later on their days off than on workdays, while 15% had a shorter cycle, meaning they woke earlier at the weekend than during the week.

The volunteers with the biggest lag in their sleep schedule between working and non-working days had worse levels of cholesterol, higher insulin resistance, a larger waist measurement and greater BMI (Body Mass Index) compared to the others, the team noted.

This "social jet lag" remained, even when the scientists adjusted for other sleep and lifestyle variables, such as physical activity and caloric intake.

"Social jetlag refers to the mismatch between an individual's biological circadian rhythm and their socially imposed sleep schedules," said Patricia M.Wong, lead author of the study. "Other researchers have found that social jetlag relates to obesity and some indicators of cardiovascular function."

"However, this is the first study to extend upon that work and 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. These metabolic changes can contribute to the development of obesity, diabetes and cardiovascular disease."