Stick to the Schedule.

• Position: PSYCHOLOGY

Not sticking to a regular bedtime and wake-up schedule--and getting different amounts of sleep each night--can put a person at higher risk for obesity, high cholesterol, hypertension, high blood sugar, and other metabolic disorders a study funded by the National Heart, Lung, and Blood Institute that appears in the journal Diabetes Care has found. In fact, for every hour of variability in time to bed and time asleep, a person may have up to a 27% greater chance of experiencing a metabolic abnormality.

"Many previous studies have shown the link between insufficient sleep and higher risk of obesity, diabetes, and other metabolic disorders, but we didn't know much about the impact of irregular sleep, high day-to-day variability in sleep duration, and timing," says study author Tianyi Huang, epidemiologist of the Channing Division of Network Medicine at Boston's Brigham and Women's Hospital. "Our research shows that, even after considering the amount of sleep a person gets and other lifestyle factors, every one-hour night-to-night difference in the time to bed or the duration of a night's sleep multiplies the adverse metabolic effect."

For the study, researchers followed 2,003 men and women, ages 45 to 84. The participants were studied for a median of six years to find out the associations between sleep regularity and metabolic abnormalities. To ensure objective measurement of sleep duration and quality, participants wore actigraph wrist watches to track sleep schedules closely for seven consecutive days. They also kept a sleep diary and responded to standard questionnaires about sleep habits and other lifestyle and health factors. Participants completed the actigraphy tracking between 2010-13 and were followed until 2016-17.

"Objective metrics and a big and diverse sample size are strengths of this study, as is the study's ability to look not only at current factors, but to conduct a prospective analysis that allowed us to assess whether patterns of irregular sleep could be linked to future metabolic abnormalities," says...