Research highlights – 29 July 2011

Research questions“Research highlights” is a weekly round-up of research papers appearing in the print BMJ. We start off with this week’s research questions, before providing more detail on some individual research papers and accompanying articles.

What are the benefits of intensive glucose lowering treatment for mortality in adults with type 2 diabetes?

As shown by the spat between the German Diabetes Association and Germany’s drug evaluation agency (BMJ 2011;343:d4609), the controversy around intensive blood glucose control for type 2 diabetes is ongoing. Now Rémy Boussageon and colleagues have carried out an updated meta-analysis to evaluate microvascular complications, cardiovascular events, and severe hypoglycaemia related to intensive glycaemic control and the level of evidence of the selected studies.

Their conclusions are not encouraging: no benefit of treatment on all cause mortality or death from cardiovascular causes; a 10% reduction in the risk of microalbuminuria, but without significant benefit on other important microvascular complications; and the favourable results on non-fatal myocardial infarction and microalbuminuria did not remain significant when the analysis was restricted to studies of high quality, whereas a 47% increase in the risk of congestive heart failure became significant. There was also a twofold increased risk of severe hypoglycaemia.
In their accompanying editorial, David Preiss and Kausik Ray write that the study “is consistent with earlier evidence that the cardiovascular benefit of intensive glucose lowering seems to be modest at best, and that glucose lowering is probably less efficacious and more difficult to achieve than lipid lowering and blood pressure control.”

Diet and diverticular disease

Diverticular disease has been called a “disease of Western civilisation” because of its high prevalence in countries like the UK and United States compared with parts of Africa. Its prevalence in the UK has been rising and is expected to increase further, owing to its association with age. Dietary factors, including consumption of fibre and meat, are also thought to play a part in diverticular disease, but supporting evidence is scarce.

Francesca Crowe and colleagues’ prospective cohort study in England and Scotland shows a reduced risk of admission to hospital or death from diverticular disease among vegetarians and people with a high intake of dietary fibre. Vegans had an even lower risk of diverticular disease, but this finding was based on small numbers. There was no significant association between the amount of meat consumed and the incidence of diverticular disease among meat eaters.

Other studies have found that vegetarian diets and high fibre intake are correlated with rapid bowel transit times and more frequent bowel movements, which suggests a possible biological mechanism for this study’s findings. In the full length paper online (doi:10.1136/bmj.d4131) the authors discuss this and other explanations, such as the possibility that vegetarians might be less likely to undergo investigations and be diagnosed with the disease.

In an editorial David Humes and Joe West say that modification of diet probably provides an opportunity for preventing diverticular disease at the population or individual level, although more evidence is needed before dietary recommendations can be made to the general public about the specific benefits discussed here. However, the findings lend support to existing public health recommendations about fibre intake.

Adjuvant chemotherapy for elderly patients with lung cancer

Lung cancer remains a leading cause of death from cancer, predominantly in elderly people. Non-small cell lung cancer at stages I to IIIA is still potentially resectable and curable, but with a rate of recurrence of 40-65% in the more advanced stage II or IIIA disease. So, evidence from clinical trials that adjuvant platinum based chemotherapy improves survival in such patients has been welcomed. 

Unfortunately, like most clinical trials, these studies have tended to exclude patients with comorbidities and have thus weeded out many elderly patients—the group with most to gain from the treatment, but also most likely to be vulnerable to the toxic effects of chemotherapy.

Using data from a nationally representative cancer registry, Juan Wisnivesky and colleagues have shown that chemotherapy was associated with improved survival in 684 patients aged over 65 with resected stages II-IIIA lung cancer.  However, the beneficial effects did not extend to the relatively few patients aged 80 or over, nor did the study look at patients’ quality of life. 

The accompanying editorial by Béatrice Fervers discusses the results further, but the basic message for treating clinicians seems to be that although their concerns about adverse effects of adjuvant chemotherapy in elderly patients are not unfounded, they can afford to raise the cut-off point for age.

Effect of pregnancy planning and fertility treatment on cognitive outcomes in children at ages 3 and 5

C Carson and colleagues’ UK cohort study showed no adverse effect of planned pregnancy, subfertility, or assisted reproduction on children’s cognitive development (doi:10.1136/bmj.d4473).

Patients’ and family members’ views on how clinicians enact and how they should enact incident disclosure In this qualitative study, Rick Iedema and colleagues investigated perceptions and experiences of how doctors communicate about serious healthcare incidents, and how the situation might be improved(doi:10.1136/bmj.d4423).