Metabolic syndrome is a cluster of health conditions that can increase the risk of developing type 2 diabetes, stroke, heart disease, and other serious illnesses.
The researchers in the latest study looked at the relationship between variability of sleep pattern and the development of metabolic risk factors in 2,003 people aged between 45 and 84 years.
They found that for every 1 hour of day-to-day variation in bedtime or length of sleep, there was a 27% raised risk of developing metabolic risk factors.
The National Heart, Lung, and Blood Institute (NHLBI), which is part of the National Institutes of Health, funded the study, which features in the journal Diabetes Care.
"Many previous studies," says corresponding study author Tianyi Huang, who works as an epidemiologist at Brigham and Women's Hospital in Boston, MA, "have shown the link between insufficient sleep and higher risk of obesity, diabetes, and other metabolic disorders."
What these studies did not clarify, however, was whether irregularity in the pattern of bedtime and length of sleep might also be a factor.
"Our research shows that, even after considering the amount of sleep a person gets and other lifestyle factors, every 1-hour night-to-night difference in the time to bed or the duration of a night's sleep multiplies the adverse metabolic effect," Huang adds.