Intended for healthcare professionals


Tom Nolan’s research reviews—16 June 2022

BMJ 2022; 377 doi: (Published 16 June 2022) Cite this as: BMJ 2022;377:o1447
  1. Tom Nolan, clinical editor; sessional GP, Surrey
  1. The BMJ, London

No thanks, I’m sweet enough

I wonder how much coffee gets drunk by academics as they try to grind out another research paper? Should author coffee consumption—or addiction—be disclosed on research papers about the health benefits of coffee? This prospective cohort study, where no coffee drinking interests were declared, finds moderate consumption of unsweetened and sugar sweetened coffee was associated with a lower risk of death over a median follow-up period of seven years. Data from the UK Biobank was used, which meant the authors could adjust for possible confounders such as education level, deprivation, physical activity, and even tea and milk consumption. But residual confounding and other methodological limitations mean this study still can’t prove that it’s all down to the coffee. Perhaps a randomised control trial is needed, but I’m not sure it’s ethical to make people drink sugary coffee, let alone coffee with artificial sweetener—which in the current study wasn’t associated with the same survival benefit.

Ann Intern Med doi:10.7326/M21-2977

Worrying stats for sats

A retrospective cohort study based in the US sheds further light on pulse oximeter bias associated with race and ethnicity, this time in patients hospitalised with covid-19. Occult hypoxaemia is when the true arterial blood oxygen saturation levels are less than 88%, but the pulse oximeter is still giving a reading of 92-96%. In the 1216 patients who had concurrent pulse oximeter and arterial oxygen levels measured, occult hypoxaemia was identified in 3.7% of samples from black and Asian patients, versus 1.7% of samples from white patients. The chances of patients having at least one incidence of occult hypoxaemia during their admission were remarkably high: 30.2% in Asian patients, 28.5% in black patients, and 17.2% in white patients. An accompanying editorial says that this is a fixable problem—the technology exists to make more accurate, non-racist pulse oximeters—but, unless practitioners and those responsible for healthcare systems push for change, things will likely stay as they are.

JAMA Intern Med doi:10.1001/jamainternmed.2022.1906

(CAR) T blanche

The New England Journal of Medicine has enthusiastically kicked off a new article series called “Science behind the Study,” declaring that few things are more exciting than a potential new treatment for an incurable illness. Reading through the first article in the series reminded me that there are few things I find more difficult to understand than gene therapy. The new treatment is chimeric antigen receptor (CAR) T cell therapy, which was used in two patients with metastatic prostate cancer, leading to a response in one: a partial regression of visceral metastasis that was sustained at six months.

N Engl J Med doi:10.1056/NEJMoa2119662

Blocking programmed death

Next on the journal’s new treatments round-up comes an immunotherapy for rectal cancer that works by the promisingly named mechanism of programmed death 1 (PD-1) blockade. Around 5-10% of rectal adenocarcinomas lack DNA mismatch repair enzymes, and are therefore less responsive to chemotherapy and radiotherapy. However, PD-1 blockade has previously shown promising results in those with mismatch repair-deficient metastatic disease. This new phase 2 study recruited 12 patients with mismatch repair-deficient stage II or stage III rectal cancer and gave them dostarlimab, an anti-PD-1 monoclonal antibody, every three weeks for six months. All 12 patients had complete remission, sustained at follow-up, between six and 25 months later: no evidence of tumour was found on magnetic resonance imaging, positron emission tomography, endoscopy, biopsy, or digital rectal examination. None of the patients has needed chemotherapy, radiotherapy, or surgery, and none has experienced severe adverse events. This is only a small study from a single site, with relatively short follow-up, but, with such dramatic results, it’s not surprising that this study made the headlines.

N Engl J Med doi:10.1056/NEJMoa2201445

Bariatric surgery and cancer risk

A retrospective cohort study of over 30 000 patients with a body mass index of over 35 found that those who had bariatric surgery had a lower risk of obesity associated cancers and cancer related mortality. After 10 years, 2.9% of those who had bariatric surgery and 4.9% of matched controls had a diagnosis of obesity associated cancer: that gives a hazard ratio of 0.68. Possible selection bias (differences in those who come forward for or who could access bariatric surgery) and healthy user bias (healthier lifestyles during the follow-up period in those who undergo surgery) seem to raise big question marks over the degree to which bariatric surgery itself lowers these risks. It seems that—as with coffee drinking—we may need further evidence from randomised trials.

JAMA doi:10.1001/jama.2022.9009


  • Competing interests: None declared

  • Provenance and peer review: Not commissioned, not peer reviewed.