Date Published: January 29, 2019
Publisher: Public Library of Science
Author(s): Lauren Lapointe-Shaw, Chaim M. Bell
Abstract: Chaim M. Bell and Lauren Lapointe-Shaw discuss the meaning of the “weekend effect” in outcomes for hospital admissions and surgeries, and comment on surprising new results published in PLOS Medicine this week.
Partial Text: Since the weekend effect was first described, many have wondered whether it results from variation in care or simply differences in the risk profiles of weekend and weekday patients [2–4]. Methods to adequately account for possible confounders between weekend care and patient outcomes are essential to attribute differences in outcomes to differences in care. Yet, most studies of the weekend effect have relied on administrative data sources and thus have been limited to readily available measures of baseline risk, such as age, sex, comorbidity counts, and previous healthcare usage. These commonly included variables offer little information on severity of illness, as they are mostly limited to health status prior to the current presentation.
Patients undergoing surgery on weekends have been found, in some cases, to experience worse outcomes than those operated on weekdays. Notably, studies of elective procedures have identified a significant weekend effect (with an odds ratio for mortality on the order of 1.8 or 1.9) [18,19], yet urgent procedures have demonstrated no such effect [20–22]. This finding is unexpected, as elective surgeries, by their planned nature, should be more likely to exhibit consistent outcomes throughout all days of the week. That the inverse occurs suggests a similar phenomenon to that observed for elective medical admissions. The large drop in elective surgical admissions and procedures on weekends may be introducing significant bias on the basis of differences in unmeasured severity of illness.
Previous research has indicated that, in many cases, weekend-admitted patients are sicker than weekday-admitted patients. Large differences in volumes and outcomes for weekend elective patients raise the possibility of confounding on the basis of patient risk profiles. The study by O’Leary and colleagues convincingly demonstrates a large weekend effect for weekend-admitted elective patients who subsequently undergo surgery. However, we need a better understanding of how elective weekend patients may be different. Otherwise, any implementation of widespread staffing or protocol changes would be premature.