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Research Christmas 2013: Research

The survival time of chocolates on hospital wards: covert observational study

BMJ 2013; 347 doi: (Published 14 December 2013) Cite this as: BMJ 2013;347:f7198
  1. Parag R Gajendragadkar, cardiology specialist registrar1,
  2. Daniel J Moualed, ENT surgery specialist registrar2,
  3. Phillip L R Nicolson, haematology specialist registrar3,
  4. Felicia D Adjei, core medical trainee1,
  5. Holly E Cakebread, foundation year doctor1,
  6. Rudolf M Duehmke, cardiology specialist registrar1,
  7. Claire A Martin, cardiology specialist registrar1
  1. 1Department of Cardiology, Bedford Hospital, Bedford MK42 9DJ, UK
  2. 2Department of Ear, Nose and Throat Surgery, Great Western Hospital, Swindon, UK
  3. 3Department of Haematology, University Hospital of North Staffordshire, Stoke-on-Trent, UK
  1. Correspondence to: P R Gajendragadkar gajendragadkar{at}
  • Accepted 28 November 2013


Objective To quantify the consumption of chocolates in a hospital ward environment.

Design Multicentre, prospective, covert observational study.

Setting Four wards at three hospitals (where the authors worked) within the United Kingdom.

Participants Boxes of Quality Street (Nestlé) and Roses (Cadbury) on the ward and anyone eating these chocolates.

Intervention Observers covertly placed two 350 g boxes of Quality Street and Roses chocolates on each ward (eight boxes were used in the study containing a total of 258 individual chocolates). These boxes were kept under continuous covert surveillance, with the time recorded when each chocolate was eaten.

Main outcome measure Median survival time of a chocolate.

Results 191 out of 258 (74%) chocolates were observed being eaten. The mean total observation period was 254 minutes (95% confidence interval 179 to 329). The median survival time of a chocolate was 51 minutes (39 to 63). The model of chocolate consumption was non-linear, with an initial rapid rate of consumption that slowed with time. An exponential decay model best fitted these findings (model R2=0.844, P<0.001), with a survival half life (time taken for 50% of the chocolates to be eaten) of 99 minutes. The mean time taken to open a box of chocolates from first appearance on the ward was 12 minutes (95% confidence interval 0 to 24). Quality Street chocolates survived longer than Roses chocolates (hazard ratio for survival of Roses v Quality Street 0.70, 95% confidence interval 0.53 to 0.93, P=0.014). The highest percentages of chocolates were consumed by healthcare assistants (28%) and nurses (28%), followed by doctors (15%).

Conclusions From our observational study, chocolate survival in a hospital ward was relatively short, and was modelled well by an exponential decay model. Roses chocolates were preferentially consumed to Quality Street chocolates in a ward setting. Chocolates were consumed primarily by healthcare assistants and nurses, followed by doctors. Further practical studies are needed.


  • We thank the participating staff on the wards. The observers would like to apologise to anyone who received a less than truthful answer to the question: “What are you doing here?”

  • Contributors: PRG conceived the study, wrote the initial protocol, analysed the data, and wrote the first draft of the manuscript. He is the guarantor for the study. DJM developed the protocol, conducted experiments, collected data, and critically revised the final manuscript. PLRN collected pilot data, developed the protocol, conducted experiments, collected data, and critically revised the final manuscript. FDA and HEC conducted experiments, collected data, aided in data interpretation, and critically revised the final manuscript. RDM and CAM developed the protocol, and critically revised the final manuscript. All authors had access to the full dataset, take responsibility for the integrity of the data and the accuracy of the dataset, and gave final approval for the submission of this version for consideration of publication.

  • Funding: This study received no external funding. The costs of the study were borne equally by the authors. No sponsorship was obtained.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years. Other non-financial relevant interests: PRG is particularly sentimental about, and incredibly fond of, Lindt Lindor white chocolate truffles; DJM advocates abstinence as the only effective way to avoid chocolate over-consumption; PLRN is influenced by the intoxicating smells emanating from the Cadbury’s chocolate factory at Bournville near his home; FDA supports her native Ghana’s cocoa exports by eating a single Heroes chocolate (Cadbury) every night; HEC declares an interest in polishing off leftover Bounty chocolates (Mars); RDM’s Germanic background means that he is hard-wired, like his brethren, to love all milk chocolate; and CAM reports a preference for Milkybar buttons (Nestlé).

  • Ethical approval: Not sought.

  • Data sharing: A full dataset is available from the corresponding author on request.

  • Transparency: PRG (guarantor) affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned have been explained.

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