If you live in the US, daylight saving time has probably thrown your sleep schedule for a loop, but the good news is that if you’re working on getting back to a regular sleep and wake time, researchers have new insights into what time you should be striving for.

Researchers from UK Biobank analyzed 88,000 volunteers and followed each patient for seven days, tracking their sleep and wake times as well as other metrics like heart rate, breathing, and sleep cycles. They then followed these patients for several years, checking up on their heart and circulatory health over an average of six years.

What they found was that a bedtime between 10 and 11 pm was linked to lower levels of cardiovascular disease. This remained true even when the researchers accounted for factors like sleep duration and sleep irregularity.

Although the researchers cannot prove cause and effect quite yet, the results of their long-term study are striking. They believe the benefits of this sleep time are linked to the fact that it allows the body to follow natural circadian rhythms. Study author Dr. David Plans said, “The riskiest time was after midnight, potentially because it may reduce the likelihood of seeing morning light, which resets the body clock.”

Source study: European Heart Journal – Accelerometer-derived sleep onset timing and cardiovascular disease incidence: a UK Biobank cohort study