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Higher weekend death rate is flawed, study finds

BMJ 2016; 353 doi: https://doi.org/10.1136/bmj.i2598 (Published 06 May 2016) Cite this as: BMJ 2016;353:i2598

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Re: Higher weekend death rate is flawed, study finds

While debate on the so called “weekend effect” is welcome, Meacock et al’s [1] conclusion that “sicker patients are admitted at weekends than during the week” explain this effect is simply not supported by their own data.

Their main premise that patients admitted at the weekend are sicker because of a higher admission threshold, especially those admitted directly, is contradicted by data presented in Table 3. The crude relative risk for direct admissions is 1.15 (2.72%/2.37%) but the adjusted relative risk is higher at 1.21 [2]: this implies that patients admitted at the weekends are actually less sick than those admitted during the week (yet still have a higher risk of death). This this can also be seen in their appendices, where not only was there a lower proportion of patients admitted aged 65 years or older, but that out of the 27 co-morbidities examined, 23 were present in lower proportions in patients admitted at the weekend compared with weekdays. Even for admissions via A&E, in Table 2, the crude relative risk is 1.05 (3.57%/3.42%), which is exactly the same as the risk-adjusted relative risk 1.05[2]: this implies there is no difference in the “sickness” of patients admitted at weekends vs. weekdays. Interestingly, we found in our original paper[3] of 2010 that patients admitted as an emergency on a weekend had a 7% higher risk of death compared with weekdays, and that risk adjustment also made no difference to this figure, suggesting again that patients admitted on a weekend were no sicker than those admitted during the week.

The use of A&E attendances as a denominator is inappropriate, given differences in the type of patients attending A&E by day of the week and the different subsets of patients attending (medical, surgical, oncology etc.). A&E attendances are not the issue, and Meacock et al’s finding that “Higher mortality rates at weekends are found only amongst the more restricted subset of patients who are admitted” is not novel – and we are not aware that anyone has published anything to the contrary.

Although the idea of sicker emergency patients admitted at the weekend explaining the so-called “weekend effect” is seductive, unfortunately Meacock et al’s evidence seems to suggest the opposite is true. Their evidence runs counter to their hypothesised higher admission threshold at the weekend. In addition, their supposition does not explain the increasing body of UK evidence suggesting a higher risk of death (and other adverse outcomes) at the weekend in yet more groups of patients and/or other datasets including elective surgery,[4] maternity [5,6] and in-hospital cardiac arrest.[7]

REFERENCES
[1] Meacock R, Anselmi L, Kristensen SR, Doran T, Sutton M. Higher mortality rates amongst emergency patients admitted to hospital at weekends reflect a lower probability of admission. J Health Serv Res Policy 2016. doi:10.1177/1355819616649630
Supplemental table at http://hsr.sagepub.com/content/suppl/2016/05/04/1355819616649630.DC1/App...

[2] Grant R. Converting an odds ratio to a range of plausible relative risks for better communication of research findings. BMJ 2014;348:f7450

[3] Aylin P, Yunus A, Bottle A, Majeed A, Bell D. Weekend mortality for emergency admissions. A large, multicentre study. Qual Saf Health Care 2010;19:213-7

[4] 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;346:f2424

[5] Palmer WL, Bottle A, Aylin P. Association between day of delivery and obstetric outcomes: observational study. BMJ 2015;351:h5774.

[6] Pasupathy D, Wood AM, Pell JP, Fleming M, Smith GC. Time of birth and risk of neonatal death at term: retrospective cohort study. BMJ 2010;341:c3498.

[7] Robinson E, Smith G, Power S, Harrison D, Nolan J, Soar J, Spearpoint K, Gwinnutt C, Rowan K. Risk-adjusted survival for adults following in-hospital cardiac arrest by day of week and time of day: observational cohort study. BMJ Qual Saf 2015. http://dx.doi.org/10.1136/bmjqs-2015-004223

Competing interests: Co-Director of Dr Foster Unit at Imperial. Previously published research suggesting a " weekend effect".

10 May 2016
Paul Aylin
Professor
Alex Bottle, Derek Bell
Imperial College London
Dept. of Primary Care and Public Health, School of Public Health, Reynolds Building, St Dunstan's Road, London W6 8RP