Surgery can be a scary prospect. Whether you are scheduled for minor skin cancer surgery or a triple bypass on your heart, allowing yourself to go under the knife can produce understandable anxiety.

One fact that may help calm your nerves is that if you schedule your surgery in the morning, you will be at a lower risk for surgical errors than you would be if you scheduled your surgery for the afternoon, according to Duke University researchers.

There are two fundamental reasons why afternoon surgical patients are at a higher risk for surgical errors. The first is that mid-afternoon is when most surgical teams experience a shift change. As a result, your team could even change mid-surgery. Most shifts in surgical wards begin at 6:30 or 7:00 a.m. When factoring in a standard work day with a standard lunch break, mid to late afternoon surgeries are often affected by this shift.

In addition, a biological factor plays into patient safety during afternoon surgery. Between roughly 3:00 and 5:00 p.m. the human body experiences a natural dip in circadian rhythms. These rhythms affect our brain wave activity as well as our alertness. For many people, this dip results in a normal feeling of sleepiness. This circadian dip does not benefit patients being treated by sleepy doctors.

Duke researchers determined that patients are most at risk when they schedule surgeries to begin between 3:00 and 4:00 p.m. However, the safest bet may be to schedule your surgery on a day when it can be performed first thing in the morning.