Research highlights – 10 September 2010

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.

Eat your greens

Patrice Carter and colleagues’ systematic review of studies on the effects of fruit and vegetables on incidence of type 2 diabetes looked at six eligible prospective cohort studies that assessed the diet of more than 220, 000 adults. Increased consumption of green leafy vegetables was associated with a significantly lower risk of diabetes, but no link was found with eating more fruit or (unspecified) vegetables, or both.

In the linked editorial Jim Mann and Dagfinn Aune highlight the authors’ recommendation that an extra portion and a half of spinach or other greens a day can cut the risk of diabetes by 14%, independently of any effect of weight loss. But they are worried that this message is too narrow and might undermine efforts to get everyone eating five portions of fruit and veg a day.

Oral bisphosphonates and risk of oesophageal cancer

Hot on the heels of the recent meta-analysis by Mark Bolland and colleagues on the cardiovascular risks associated with taking calcium supplements comes Jane Green and colleagues’ study about the risk of cancer when taking oral bisphosphonates. This nested case-control analysis of 6 million people in the UK General Practice Research Database—including nearly 3000 people aged 40 or older with oesophageal cancer, around 2000 with gastric cancer, and more than 10,000 with colorectal cancer—found that those prescribed oral bisphosphonates 10 or more times, or for about five years, had a significantly raised relative risk of oesophageal cancer. In Europe or the United States this equates to an increase in cancer incidence from about one case per 1000 population over five years to about two cases per 1000 people with five years’ use of oral bisphosphonates at age 60-79.

What should patients wanting to avoid or treat osteoporosis make of such studies? Editorialist Diane Wysowski argues that this latest evidence on oral bisphosphonates is inconclusive and that any risk of cancer must be small, but gives practical advice on minimising oesophageal irritation from these pills.

Leap in surgery for obesity

No one needs reminding what a big issue obesity is. The NHS (and the independent sector) is taking the problem seriously, judging by the results of Elaine Burns and colleagues’ observational population cohort study on the provision of surgery for obesity.

The number of bariatric surgery procedures carried out in England increased tenfold in eight years—from 238 in 2000-1 to 2543 in 2007-8—with the proportion performed using minimally invasive laparoscopic techniques increasing from 28% to 74.5%. This increase didn’t have any effect on safety though: there was no variation over the study period in postoperative mortality, mortality at one year, or readmissions.

The authors suggest the number of procedures could well continue to increase. Coauthor Omar Faiz told Associated Press: “We don’t know whether we’ve seen the summit of the peak, but the trend still looks to be going upwards.”

Research online: For these and other new research articles see

Isoniazid resistance and death from tuberculous meningitis

In this retrospective cohort study, Christopher Vinnard and colleagues looked at the relation between isoniazid resistance and subsequent death in patients with tuberculous meningitis, the most devastating form of tuberculosis. Isoniazid is the only first line antituberculous drug that has bactericidal activity throughout treatment and freely penetrates the blood-brain barrier, properties that are relevant for clinical cure in other types of bacterial meningitis. Clinicians therefore suspected that isoniazid resistance could affect the outcome of tuberculous meningitis to an extent not seen in pulmonary tuberculosis.

This assessment, which included 1896 patients treated for an initial episode of tuberculous meningitis in the United States, did indeed show an association between initial isoniazid resistance and subsequent death in those with cerebrospinal fluid cultures positive for Mycobacterium tuberculosis.

In an accompanying editorial, Bjørn Blomberg and Nina Langeland say that the findings emphasise the importance of actions to contain drug resistance, firstly by prudent use of antituberculous drugs.