Ann Robinson’s research reviews—20 August 2021

Ann Robinson reviews the latest research from the top medical journals

US children get two thirds of their energy intake from ultra-processed foods

Here’s an unsurprising but shocking fact: US children (2-19 years old) get most of their daily calories from ultra-processed food, and that proportion is increasing. This large cross-sectional US study found that the percentage of total calories derived from ultra-processed food rose from 61.4% in 1999 to 67% in 2018. Minimally or unprocessed food (typically home cooked food) made up 28.5% of energy intake in 1999, falling to 23.5% by 2018. It’s a trend that reflects the well documented rise in childhood obesity, and it seems likely that the two are connected. Children are getting more of their energy from ready meals (increasing from 2.2% to 11.2%) and around the same percentage from sweet snacks (from 10.7% to 12.9%). They get 5.5% fewer calories from sugary drinks and 3% less from sauces and oils. The biggest increase and highest overall proportion of ultra-processed foods was among young non-Hispanic black populations, followed by Mexican Americans. The findings relied on self reported dietary recall, which can be unreliable, and the NOVA classification system of foods that some claim is over simplistic. Despite these caveats, the data are compelling, credible, and depressing.

JAMA doi:10.1001/jama.2021.10238

Prison overcrowding increases the risk of covid-19

Covid-19 thrives in crowded prisons that exceed their design capacity and have fewer single cells, according to this longitudinal ecological study (designed to study a specified group of people) of 6876 prisoners in 14 Massachusetts state prisons from April 2020 to January 2021. The mean covid-19 incidence in prisons was six times greater than in the surrounding population, and rates rose with the degree of overcrowding (14% increase in covid incidence for every 10% increase in capacity, and an 18% fall in incidence for every 10% increase in prisoners housed in single cells). There could be other unknown variables at play, and the true incidence of covid may have been higher as testing did not include asymptomatic cases. Prisoners who catch covid are more likely to die of it than the general population, so steps to mitigate the risks, such as reducing overcrowding, are urgently needed.

JAMA Intern Med doi:10.1001/jamainternmed.2021.4392

Incompletely resected polyps risk future and more advanced cancer

What happens to neoplastic colorectal polyps that are incompletely resected? This small observational cohort study of 166 patients who had a surveillance colonoscopy as part of the CARE study (Complete Adenoma REsection study 2009-12) found an increased risk of metachronous neoplasia (that is, a second primary cancer diagnosed more than six months after the first) in segments with incomplete versus complete resection (52% v 23%). Advanced cancer was more likely in segments that had incompletely resected polyps compared with fully resected ones (18% v 3%). Further work is needed, not least because of incomplete patient follow-up, which may have introduced bias, and the relatively small numbers involved.

Ann Intern Med doi:10.7326/M20-6689

Two doses of Pfizer and AstraZeneca vaccines effective against the delta variant

This useful test-negative case-control analysis found that both the Pfizer and Oxford/AstraZeneca vaccines were effective against symptomatic covid-19 due to the delta variant (now the most common variant in the UK and spreading rapidly elsewhere) and only slightly less effective against the alpha variant. After a single dose of vaccine, effectiveness against the delta variant was limited (36% estimated effectiveness with Pfizer, 30% with AZ), but two doses conferred good protection (88% effectiveness with Pfizer, 67% with AZ). The findings were observational, so need to be treated with caution. PCR testing is imperfect and may have skewed results by detecting one variant more than another, and populations at greater clinical risk may have been more likely to be given the AZ rather than Pfizer vaccine, which would have further muddied the waters.

N Engl J Med doi:10.1056/NEJMoa2108891

Hope for adults with refractory leukaemia

The ZUMA-3 phase 2 study is an international, multicentre trial of chimeric antigen receptor (CAR) T cell therapies targeting the CD19 protein for adults with relapsed or refractory B-precursor acute lymphoblastic leukaemia. Outcomes in these patients are generally poor. The researchers found that a single infusion of the novel therapy KTE-X19 produced remission (complete remission in 56%, partial remission in 71%) in a small group of patients. Median overall survival was 18.2 months, and the safety profile was described as “manageable” with no deaths due to cytokine release syndrome. The single-arm design is a potential limitation, and longer follow up of safety and efficacy are needed.

Lancet doi:10.1016/S0140-6736(21)01222-8

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