research suggests there may be a “better” time of day for heart surgery, but the effect is modest and not yet definitive.
What the latest research found
- A 2026 study analyzing over 24,000 heart-surgery patients found late-morning operations (10:00–11:59 AM) had the highest risk of cardiovascular death compared with other times.
- The data showed about an 18% higher risk of heart-related death for late-morning surgeries compared with early-morning (7–10 AM) procedures.
- Early-afternoon surgeries (12–2 PM) actually showed lower predicted risk than late-morning cases.
Why timing might matter
Researchers think it’s linked to the body’s circadian rhythm (internal biological clock):
- Heart cells may tolerate stress better later in the day
- Hormones, blood pressure, and clotting ability change across the day
- Surgical team fatigue and hospital workflow may also play a role
But the science is mixed
- Some earlier reviews found no meaningful difference between morning vs afternoon surgery outcomes.
- Other studies suggested afternoon surgery might reduce complications, but results aren’t consistent across all hospitals and procedures.
Bottom line
- There may be a slight advantage to early morning or early afternoon
- Late-morning surgeries showed slightly higher risk in one large study
- However, timing is far less important than:
- surgeon experience
- hospital quality
- patient condition
- urgency of surgery
Doctors emphasize that patients shouldn’t delay necessary heart surgery just to choose a time slot — the overall care team matters much more.
