Working at night is a necessary part of some jobs. But working the night shift disrupts the normal sleep/wake cycle, and researchers have found it takes a physical toll, raising your risk for diabetes and heart disease. Now a study suggests working regular daytime hours and having to wake up early during the week at a time that isn’t in synch with your natural circadian rhythm may also be harmful to health.
Your circadian rhythm is your personal internal clock — a 24-hour cycle marked by periods when you need sleep and other times of alertness. It influences many other physiological processes, too. But not everyone’s internal clock ticks exactly the same. There’s variation in circadian rhythms, which explains why you might be more of a “morning person” or “evening person,” according to the National Sleep Foundation.
University of Pittsburgh researchers looked at the sleep cycles of 447 healthy adults between the ages of 30 and 54 who worked either part-time or full-time during the day to see whether sleep patterns corresponded to certain health risks. Each study participant wore a wristband that measured their activity and sleep 24 hours a day for a week. In addition, questionnaires were used to document the research subjects’ diets and exercise habits.
The results showed 15 percent of the research subjects had an earlier halfway point in their natural sleep cycles — a measurement known as midsleep — even on non-working days. So waking up early on weekdays seemed to be coordinated with their internal clock.
But nearly 85 percent of the study participants experienced a later midsleep point at night when they didn’t have to get up early, indicating their natural sleep cycle was disrupted when they were forced to wake up early to go to work — a phenomenon the researchers call social jetlag (SNL).
Those with SNL were more likely to have unhealthy cholesterol levels, higher fasting blood sugar, and obesity, all risk factors for type 2 diabetes, heart disease, and other health conditions. The association between the potential health risks persisted even when the researchers accounted for other lifestyle factors, including how much those with SNL exercised and how many calories they consumed.
"Social jetlag refers to the mismatch between an individual's biological circadian rhythm and their socially imposed sleep schedules. Other researchers have found that social jetlag relates to obesity and some indicators of cardiovascular function," said researcher Patricia M. Wong, a PhD student at the University of Pittsburgh.
"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."
In fact, sleep disruption is believed to be one of the factors contributing to the rising rates of diabetes and obesity in the U.S., according to the Endocrine Society's Endocrine Facts and Figures report. Wong suggests it could be prudent to consider how modern work schedules and social obligations affect 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,” she said.
March 21, 2016
Janet O’Dell, RN