“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.
- Are white matter hyperintensities on brain magnetic resonance images associated with risk of stroke, cognitive decline, dementia, and death?
- Do calcium supplements (without coadministered vitamin D) affect the risk of cardiovascular events?
- Is there an association between genus β human papillomaviruses and incidence of non-melanocytic skin cancer in the general population?
- How much inequality exists in premature mortality in Britain?
Calcium supplements and myocardial infarction
Two years ago Mark J Bolland and colleagues investigated, in a secondary analysis of their own randomised controlled trial in postmenopausal women, the association between calcium supplementation and cardiovascular outcomes. They found that the number of women needed to treat (NNT) for five years to prevent one symptomatic fracture was 50 but the corresponding number to cause one myocardial infarction was 44, to cause one stroke was 56, and to cause one cardiovascular event was 29. This proved highly controversial, as the many Rapid Responses attest.
Now the same authors’ meta-analysis of trials including around 12,000 men and women reports a modestly increased risk of myocardial infarction that was consistent across trials and was independent of age, sex, and type of supplement. They acknowledge the limitations that the trials were not of combined calcium and vitamin D and none had cardiovascular events as primary endpoints, but they call for a closer look at the effectiveness and risks of calcium supplementation. Editorialist John Cleland wonders why calcium might damage vasculature when you’d expect it to improve blood pressure and lipid profiles, and suggests that calcium supplements might simply be causing gastrointestinal symptoms that could be misdiagnosed as cardiac chest pain. Nonetheless, he concludes that patients with osteoporosis should generally not take calcium supplements, either alone or combined with vitamin D, unless they are also taking an effective treatment for osteoporosis for a recognised indication.
β human papillomaviruses and squamous cell carcinoma
Margaret R Karagas and colleagues helpfully remind us in the full version of their paper that “papillomaviruses are epitheliotropic, non-enveloped, double stranded DNA viruses, of which more than 100 different types have been identified” (BMJ 2010;341:c2986). Many cause cancer, but although type 16 genus β human papillomavirus (HPV) is associated with skin cancer in high risk patients, the evidence for this in the general population was shaky. Now their large population based case control study in New Hampshire finds a significant association between this type of HPV and squamous cell carcinoma in adults. This finding was regardless of age, level of education, smoking status, skin sensitivity to the sun, or number of painful sunburn episodes.
Mind the mortality gap
In his speech as incoming president of the BMA this summer Michael Marmot cited stark evidence from his team’s recent report Fair Society Healthy Lives (www.marmotreview.org), saying “if everyone over 30 had the mortality rate as low as those with university education we could prevent 202,000 premature deaths, EACH YEAR” and “When I last looked we had found $9 trillion to bail out the banks. For one ninetieth of the money we found to bail out the banks every urban dweller could have clean running water” (BMJ 2010;341:c3617).
Bethan Thomas and colleagues add further gloomy evidence, finding in their study of individual mortality data between 1921 and 2007 that the gap in life expectancy between rich and poor in Britain continues to widen. They dedicate their paper to epidemiologist and social campaigner Jerry Morris, who died last year and who was famous for—among many other things—identifying the relation between deprivation and infant mortality, the minimum income for older people to stay healthy, and the evidence that (in bus conductors and postmen) exercise prevents heart attacks (BMJ 2009;339:b4679).
For these and other new research articles see www.bmj.com/channels/research.dtl
Don’t dismiss diet in diabetes
Recently we published online a paper reporting the success of an intensive dietary intervention at improving glycaemic control and anthropometric measures in patients with type 2 diabetes (doi:10.1136/bmj.c3337). The research has attracted comments from several advocates of lifestyle interventions for diabetes. Dario Giugliano and Katherine Esposito from Naples, Italy, criticise the “drug intensive style of medicine fuelled by the current medical literature,” whereas Rachel Taylor, a patient with type 2 diabetes from New Zealand, describes how lifestyle changes helped lower her glycated haemoglobin concentration from 8.4% to 6% in six months.