By Robert Preidt
WEDNESDAY, Nov. 18, 2015 (HealthDay News) -- Waking early on workdays and sleeping in on days off may not be as restful as you think: a new study suggests that when routine sleep habits are disrupted, your risk for diabetes and heart disease rises.
The study included 447 men and women, aged 30 to 54, who worked at least 25 hours a week outside the home. They each wore a wristband that recorded their sleep and movement 24 hours a day for a week. Questionnaires were used to assess their exercise and eating habits.
Nearly 85 percent of the participants slept longer on their days off than on workdays, the investigators found. The rest woke earlier on their days off than on workdays.
Those with large differences in their sleep schedules on workdays and free days tended to have worse cholesterol and fasting insulin levels, greater insulin resistance, larger waist size, and higher body mass index (BMI), the findings showed. BMI is an estimate of body fat based on height and weight.
This link between what the researchers called "social jetlag" and the health risk factors persisted even after adjusting for other measures of sleep and lifestyle behaviors, such as physical activity and calorie intake. The study findings were published Nov. 18 in the Journal of Clinical Endocrinology & Metabolism.
"Social jetlag refers to the mismatch between an individual's biological circadian rhythm [body clock] and their socially imposed sleep schedules. Other researchers have found that social jetlag relates to obesity and some indicators of cardiovascular function," study author Patricia Wong, of the University of Pittsburgh, said in a news release from the Endocrine Society.
"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," Wong said.
But, the association seen in the study does not prove a direct cause-and-effect relationship between inconsistent sleep habits and the development of these diseases.
"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," Wong said.
"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," Wong concluded.