Maybe reschedule that Friday surgery for Monday

Large cohort study adds evidence for the "weekend effect"

Any self-respecting surgeon or anesthesiologist will tell you that patients undergoing surgery before the weekend receive just as high a quality of care as those operated on earlier in the week.

Is it true?

The Weekend Effect

For decades, researchers have tracked a concerning signal that patients undergoing surgery later in the week experience higher rates of complications, including death.

The latest evidence for the so-called “weekend effect” comes from a large retrospective observational cohort study in JAMA Network Open.

Ranganathan et al reviewed the outcomes for 429,691 patients undergoing commonly performed surgeries on Friday or Monday (or Tuesday after a holiday weekend) in multiple hospitals in Ontario, Canada, from 2007 to 2019. Twenty-five elective and emergency surgeries were included; about half the total cohort was in each group (pre/post weekend).

Those in the Friday group had an increased risk by 5% for the primary composite outcome of death, complications, and readmissions at 30 days, 90 days, and 1 year after their operations (adjusted odds ratio ≥1.05, statistically significant).

Their risk of death was also independently increased at 30 days, 90 days, and 1 year (adjusted odds ratios 1.09, 1.10, 1.12, all significant).

This was retrospective, observational, and based 100% on database queries, and the usual caveats of potential bias, missing data, and inability to establish cause and effect all apply.

So, no reason to blow this out of proportion, and we’ll keep you on the Friday schedule for your bunion removal at 3 pm.

Wait, what’s that you’re looking at? Don’t look at that.

More Weekend Worries

An even larger study a decade earlier had raised concerns for worse outcomes occurring after Friday surgeries.

Among over 4 million admissions for elective surgeries in the U.K. between 2008 and 2011, patients in the U.K. having elective surgery on Fridays had a 44% increased risk of death, and surgeries on Saturday or Sunday brought an 82% increased risk of death, compared to Monday surgeries. (Aylin et al BMJ 2013)

But that was in the U.K., where they have socialized medicine and constrained budgets. You can’t extrapolate that to other countries.

The Weekend Effect in Other Countries

The weekend effect has been observed in multinational studies as well.

Among almost 3 million patients at 28 hospitals in the U.S., U.K., Australia, and the Netherlands from 2009 to 2012, patients admitted for emergency surgery on the weekend had higher adjusted odds of 30-day mortality.

For elective surgeries at most U.S. and U.K. hospitals, there was a steady increase in the odds of death with each surgical day after Monday. (Ruiz et al BMJ Quality & Safety 2015)

Ten cohort studies including over 6 million patients receiving elective surgery in developed countries were then combined in a meta-analysis. The odds of death increased with the day of the week of the surgery to an odds ratio of 1.24 on Friday (95% CI=1.10–1.38) relative to Monday. (Smith et al Medical Care 2018)

But that was “most” U.S. and U.K. hospitals. We aren’t most hospitals—we adhere to all the best care practices regardless of what day it is.

Specific Care Practices Decline Over the Weekend

Among over 27,000 patients undergoing elective colorectal surgery at 362 U.S. hospitals between 2014 and 2017, attention to postoperative practices to hasten recovery (encouraging patients to get out of bed) and reduce infections (removal of urinary catheters) both significantly declined over the weekend. (Liu et al JAMA Surgery 2020)

Hospitals with lower adherence rates had more overworked nurses.

At most hospitals, weekend staffing levels decline generally for physicians, nurses, and specialty service availability (e.g., interventional radiology, cardiac catheterization, imaging, and laboratory testing).

Weekend teams are often unfamiliar with the patients, increasing the potential for care gaps and prolonging lengths of stay.

The weekend effect even persists despite surgeons’ likely tendency to avoid scheduling their highest-risk cases on Fridays.

You can’t blame this on surgeons—we don’t control the hospital. And what about non-surgical patients?

It’s Not Just Surgical Patients

The weekend effect seems to extend to all inpatients, not just surgical patients.

In a meta-analysis of 97 studies including over 51 million patients, those admitted on weekends had a higher mortality (relative risk, 1.19; 95% confidence interval, 1.14-1.23). (Pauls et al, J Hospital Medicine 2017)

Patients with myocardial infarctions admitted on the weekend also have higher mortality overall.

But surely there are studies refuting the weekend effect—can’t we throw some of those up, like chaff from a fighter plane on evasive maneuvers?

Yeah! Chaff!

Most “Refuting” Studies At Least Partially Confirm the Weekend Effect

Several studies have found no worsened outcomes with surgeries on Fridays or the weekend, but a closer look at each reduces their power as counterfactuals.

• Dubois et al (CMAJ 2017) found no increase in 30-day mortality in a previous large Ontario database analysis of elective surgical outcomes. This is the strongest evidence against a weekend effect for most elective surgeries during regular hours. Dubois et al excluded patients with surgeries after working hours or with less than a 2-day hospital stay, and did not measure complications or readmissions, rendering it less robust than Ranganathan et al.

• Sayers et al (BMC Medicine 2017) concluded weekends did not affect outcomes in hip fracture repair in the U.K. overall—but they also found that patients with operations on Sundays had increased risk.

• Aqil et al (2018) found no weekend effect in elective orthopedic surgery in the U.K., but it was a small single-center study on low-risk elective cases, not adequately powered to find real differences.

• Carr et al (JAMA Surgery 2011) found no difference in outcomes for trauma surgery over the weekend — likely because of 24/7 staffing and readiness, which itself provides indirect evidence for a weekend effect.

Don’t Health Care Professionals Deserve Weekends, Too?

The solution is simple, if you ask health system leaders like Dr. Robert Pearl, former CEO of Kaiser Permanente’s physician group: just take away healthcare workers’ weekends.

Under the “7-Day Hospital” model, health systems would run at full staffing every day of the week in all roles in all departments. Problem solved.

Besides costing additional billions of dollars annually, this solution would leave some unaddressed questions regarding recruiting, retention, burnout, and attracting future high-performing people to healthcare professions.

Conclusions

The weekend effect is real.

For surgeries, if the latest data is representative, it’s also very small in an absolute sense.

For example, the 30-day mortality for healthy patients undergoing laparoscopic cholecystectomy is less than 1 in 1,000.

For hip replacement, it’s about 2 in 1,000.

A 5% increase in these risks is still very low (E.G., a hypothetical increase from ~1 in 1,000 on Monday to 1 in 952 on Friday.)

Complicated patients with comorbid illnesses would have higher (hypothetical) risks from a weekend effect.

Absent major changes to the culture and economics of healthcare staffing and system design, the weekend effect will persist. And as multiple factors contribute, it’s impossible to predict in any given situation.

So when a patient rolls into the ICU from the O.R. on Friday at 5:30 pm, there are good reasons why it might put your nerves on edge.

References

Ranganathan S, Riveros C, Tsugawa Y, Geng M, Mundra V, Melchiode Z, Ravi B, Coburn N, Jerath A, Detsky AS, Wallis CJD, Satkunasivam R. Postoperative Outcomes Following Preweekend Surgery. JAMA Netw Open. 2025 Mar 3;8(3):e2458794. doi: 10.1001/jamanetworkopen.2024.58794. PMID: 40036038; PMCID: PMC11880952.

Aylin P, Alexandrescu R, Jen MH, Mayer EK, Bottle A. Day of week of procedure and 30 day mortality for elective surgery: retrospective analysis of hospital episode statistics. BMJ. 2013 May 28;346:f2424. doi: 10.1136/bmj.f2424. PMID: 23716356; PMCID: PMC3665889.

Ruiz M, Bottle A, Aylin PP. The Global Comparators project: international comparison of 30-day in-hospital mortality by day of the week. BMJ Quality & Safety 2015;24:492-504.

Liu JY, Merkow RP, Cohen ME, Bilimoria K, Ko CY, Sweeney JF, Sharma J. Association of Weekend Effect With Recovery After Surgery. JAMA Surg. 2020 Oct 1;155(10):988-990. doi: 10.1001/jamasurg.2020.2618. PMID: 32845300; PMCID: PMC7450403.

Pauls LA, Johnson-Paben R, McGready J, Murphy JD, Pronovost PJ, Wu CL. The Weekend Effect in Hospitalized Patients: A Meta-Analysis. J Hosp Med. 2017 Sep;12(9):760-766. doi: 10.12788/jhm.2815. PMID: 28914284.

Carr BG, Reilly PM, Schwab CW, Branas CC, Geiger J, Wiebe DJ. Weekend and night outcomes in a statewide trauma system. Arch Surg. 2011 Jul;146(7):810-7. doi: 10.1001/archsurg.2011.60. Epub 2011 Mar 21. PMID: 21422328.