“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

• Is there an association between enterovirus infection and autoimmunity or type 1 diabetes?
• How effective was a programme for cardiovascular health promotion and disease prevention aimed at older adults?
• Is early exposure to diagnostic radiography or ultrasound scans associated with childhood cancer?
• Is there a “north-south divide” in mortality in England?
• Is concentration of C reactive protein causally relevant to coronary heart disease?
  Type 1 diabetes: an infectious link?

This week’s Practice and Clinical Review sections focus on the diagnosis and treatment of type 1 diabetes, but what causes the condition in the first place? While genetics are probably involved, infection—specifically, with enteroviruses— is also strongly suspected to play a part. But studies aiming to pin down such a link have had mixed results.

Wing-Chi G Yeung and colleagues reviewed the evidence for a link between enterovirus infection and type 1 diabetes/autoimmunity through a meta-analysis. Unlike a previous review (which found no association) they looked at studies that used molecular methods of viral detection, which is now the standard for diagnosis of current infection.  The included studies were observational and varied in nature, but the results suggest that a clinically significant association does exist.

The analysis couldn’t establish, however, whether entoviruses actually cause diabetes. Editorialists Didier Hober and Famara Sane say that prospective studies suggest an association between enterovirus infections and subsequent production of autoantibodies against pancreatic beta cells, but there’s also evidence that viruses may have a protective effect. The complexities of the viral link remain to be teased out.

It’s grim up north
The concept of a “north-south divide” in health and wealth in England—with southerners healthier and better off than their northern counterparts—has existed since as far back as 1066. Plenty has changed healthwise since the Normans conquered the country, yet this divide still persists today. But have medical advances and improvements in quality of life lessened the disparity in recent years?

John Hacking and colleagues have looked at more than 40 years of all cause mortality data to see whether this well established trend has changed since the 1960s. Having divided England into two parts with a boundary between the Wash and the Severn Estuary, they examined specific mortality rates for each year from 1965 to 2008 by age, sex, and region (north v south).

Over the past four decades (and five governments), the percentage excess deaths in the north compared with the south, the so called “northern excess mortality,” averaged 13.8% and was significantly larger for males than for females (14.9% v 12.7%). Worse, although the inequality decreased from the early 1980s to the late 1990s for both sexes, it increased significantly from 2000 to 2008. The increase was most marked among people aged 20-34, changing from no significant northern excess for 1965 to 1995 to 22.2% for 1996 to 2008. In addition, people in the north were a fifth more likely to die before the age of 75 than were people in the south.

Writing in a linked editorial, Margaret Whitehead and Tim Doran suggest that the coming government spending cuts and the switch from primary care trusts to general practice consortiums will only serve to widen the divide. “Future prospects,” they say, “look grim.”

Radiation in early life
Earlier reports suggest an association between in utero exposure to radiation from diagnostic radiography and an increased risk of childhood cancer, but do these procedures pose a risk when done in early infancy? The results of Preetha Rajaraman and colleagues’ case-control study suggest so—data from medical records showed that exposure to diagnostic radiography in the first 100 days of life was associated with a small increase in risk of all childhood cancer and leukaemia, and a significant increase in lymphoma. The possible risks were seen with radiation at doses lower than those associated with commonly used procedures such as computed tomography, indicating that such methods should be used cautiously when investigating a very young child or a pregnant woman’s abdomen or pelvis. However, no excess risk of childhood cancer was seen with in utero exposure to ultrasound scans.