Ann Robinson’s research reviews—25 September 2020

Ann Robinson reviews the latest research from the top medical journals

On-scene resuscitation beats hospital transfer

If you have a cardiac arrest in the street, your chances of survival are substantially better if resuscitation is continued on the scene rather than while you are transported to hospital, according to this Canadian cohort study. However, given the observational study design, there is potential for confounding factors. Ideally, a trial that randomises people to on-scene resuscitation or transport to hospital at a prespecified time would offer stronger evidence. But it’s notable that the intra-arrest group tended to have more favourable characteristics but still fared worse than the group treated on the scene. And most survivors who did undergo intra-arrest transport had already been stabilised (measured by return of spontaneous circulation) before they arrived in hospital.

JAMA doi:10.1001/jama.2020.14185

The genetics of stillbirth

Most cases of stillbirth remain unexplained even after extensive investigation. Around 10-20% are attributed to chromosomal abnormalities, but the precise cause is rarely found. This study used exome sequencing (a genomic technique to sequence all of the protein-coding regions of genes in a genome) in 246 stillbirths (gestation >20 weeks) and found a molecular diagnosis in 6%. Identifying a monogenic disorder helps calculate recurrence risk, plan the management of future pregnancies, and identify novel targets for treatment. Around half of the stillbirths attributable to genetic causes were due to pathogenic variants known to cause disorders in infants and adults, and a similar number were due to loss of function variants critical to in utero survival but not previously known to cause stillbirth or postnatal disease. Larger studies and more widespread use of exome sequencing are needed to improve understanding and prevention of this devastating event.

N Engl J Med doi:10.1056/NEJMoa1908753

Fitbits and sleep

Sleep duration and patterns are highly variable, and people with a high body mass index (>30) tend to sleep for a slightly shorter time than non-obese people (6.62 v 6.87 hours) and show more variability in their sleep patterns, according to this research letter, which analysed anonymised data from 200 000 Fitbit wearers. This sort of study clearly cannot determine whether being obese interferes with your sleep and/or poor sleep makes you obese. The sleep measures were estimated from accelerometers/optical sensors rather than gold standard polysomnography (although other validation studies suggest that Fitbits are likely to be accurate in measuring total sleep time). People who use wearable devices are generally richer, younger, and healthier than the population at large. The measurements of body mass index are based on self reported height and weight measurements. And there’s no information about daytime naps or about other comorbidities. We already know that poor sleep is associated with obesity and poor health outcomes. I’m not sure that this study adds anything to lose sleep over.

JAMA Intern Med doi:10.1001/jamainternmed.2020.2834

Vaccinating premature babies

Is the standard schedule of infant immunisations suitable for very preterm babies? This prospective observational study found that preterm infants given the (Dutch) routine schedule developed lower IgG levels than those born at full term, but that 95% or more still achieved protective cover against diphtheria, tetanus, pertussis, pneumococcus, and hepatitis B. The exception was Haemophilus influenzae type b (Hib); only 40.6% developed protective levels of IgG after the primary immunisation schedule and 88.1% after a booster dose. Findings from this Dutch study may not apply to other countries with different vaccines and vaccine schedules for preterm infants, but the finding about Hib certainly bears further investigation.

JAMA doi:10.1001/jama.2020.12316

Ann Robinson is an NHS GP and health writer and broadcaster.