Celebrating the weekend with late nights and lie-ins is bad for our health, according to new evidence presented at the SLEEP conference held in Boston this week.

Researchers suggest that “social jet lag”, a term coined to mean the disruption of your body clock by getting up and going to bed a certain time during the week and then pushing both back a few hours at the weekend, negatively affects our mood, energy levels, and health.

Most worryingly, though, each hour of social jet lag experienced increases our chances of developing heart disease by 11 percent.

“These results indicate that sleep regularity, beyond sleep duration alone, plays a significant role in our health," said lead author Sierra Forbush, of the Sleep and Health Research Program at the University of Arizona, in a statement. "This suggests that a regular sleep schedule may be an effective, relatively simple, and inexpensive preventative treatment for heart disease as well as many other health problems."

Forbush and colleagues studied 984 people aged 22 to 60 who took part in a community-based sleep survey, Sleep and Healthy Activity, Diet, Environment, and Socialization (SHADES), conducted at the University of Pennsylvania.

The participants took part in the Sleep Timing Questionnaire, self-reporting their week and weekend sleeping habits. The researchers calculated their jet lag hours experienced each week by comparing the midpoint of weekday and weekend sleeping hours and subtracting the weekday one. The sleep survey also had people answer questions about their overall sleep duration, insomnia, cardiovascular disease, fatigue, and sleepiness.  

The results showed that those who experienced just an hour of social jet lag a week had an 11 percent increased risk of developing cardiovascular disease. They were also 22 percent more likely to rate their overall health as good, not excellent, and 28 percent more likely to rate it as poor.

“It was particularly surprising that these effects were independent of how much sleep people got and any insomnia symptoms,” Forbush said. The National Sleep Foundation recommends adults get between 7 and 9 hours of sleep a night for optimal health benefits. 

“Physicians often tell people to think about their diet and exercise, but I think this offers an additional preventative strategy,” Forbush told New Scientist. “It’s not just about getting enough sleep, but getting regular sleep: ideally you want to be going to bed and waking up at the same time every day of the week.”

They presented their preliminary findings, the abstract of which is published in the journal Sleep, at the annual meeting of the Associated Professional Sleep Societies, a joint venture of the American Academy of Sleep and the Sleep Research Society.