Go to bed at roughly the same time every night, and wake up at roughly the same time every morning.
Sleep experts say that’s one of the most important strategies to feel refreshed. But it could also be vital for the health of your metabolism — the processes that keep your body operating.
A study in the journal Diabetes Care links irregular bedtimes to a long list of metabolic conditions: including obesity, diabetes, high cholesterol, high blood pressure, and high blood sugar.
“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.” said study co-author Tianyi Huang, an epidemiologist at Brigham and Women’s Hospital, Boston, in a statement.
It’s pretty well-established that not getting enough sleep overall increases the likelihood of metabolic dysfunction. But it’s been less clear whether an irregular sleep schedule has the same effect.
To find out, Huang and her colleague Susan Redline analysed health data drawn from more than 2,000 US adults, aged between 45 and 84, participating in the ongoing Multi-Ethnic Study of Atherosclerosis.
At one point in the study, participants wore sleep-measuring devices for a week while they kept sleep diaries and completed questionnaires on their nighttime habits.
Those with a greater night-to-night variability in their sleep timing had a higher frequency of metabolic conditions at baseline, and higher odds of developing them over about six years of follow-up.
For every extra hour of variability in time to bed and time asleep, a person may have up to a 27 per cent greater chance of a metabolic abnormality, the researchers said.
The study observes a link between sleep schedules and metabolic health, but can’t prove the former directly causes the latter. However, the researchers speculated why irregular bedtimes might have such grave effects.
At the cellular level, irregular sleep could upset the clock genes that oversee the body’s processes. At the hormonal level, it could disrupt the release of cortisol and melatonin — respectively dubbed the stress and sleep hormones. At the behavioural level, it could simply mess around the rest of your schedule — changing what time you eat, which also impacts health.
A rising number of adults report having wildly inconsistent sleep schedules due to their work and studies, social lives, and technology use. That inconsistency may eventually catch up with them.
“Our results suggest that maintaining a regular sleep schedule has beneficial metabolic effects,” said Redline, a senior physician in the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital.
“This message may enrich current prevention strategies for metabolic disease that primarily focus on promoting sufficient sleep and other healthy lifestyles.”