Spotlight on viruses and diabetes

The possible role of viruses in the development of diabetes was analyzed by two recent studies.

Researchers in Australia calculated the incidence of type 1 diabetes among children under age 15 between 1985 and 2010. Overall incidence of the disease increased by an average of 2.3% per year, with a mean incidence of 18.1 per 100,000 person-years. But the study also found a sinusoidal cyclical variation; there appeared to be a five-year cycle of peaks and troughs in diabetes incidence. This cycle closely matches one that was previously observed in Northeast England, the researchers noted.

The cycles support the idea that environmental factors could play a role in type 1 diabetes development, according to the brief report of the study, which was published online by Diabetes Care in July. Viral infections are one likely factor, although climate effects on lifestyle or other risk factors could be an alternative explanation, the study authors said. They called for future research to identify the causative factors.

Viral infection has been previously suspected as a contributor to type 1 diabetes, but another recent study suggests that cytomegalovirus (CMV) might also be a risk factor for type 2 diabetes in elderly patients. Researchers in the Netherlands compared rates of type 2 diabetes and CMV infection among 600 people age 85 or older. Of the participants who were seropositive for CMV, 17.2% had diabetes, compared to 7.9% of negative participants (P=0.016). The positive group also had higher hemoglobin A1c and nonfasting glucose, according to results published by Immunity and Ageing on Aug. 28.

The authors suggested a number of ways in which the viral infection could accelerate pancreatic failure, including directly affecting the pancreatic cells or creating a pro-inflammatory environment in the immune system generally. They noted that a significant association between CMV and type 2 diabetes had not been found in previous studies of younger patients, and that it's possible CMV could be a result instead of a cause of diabetes. However, CMV is often acquired during childhood, so that's unlikely to fully explain the association. The authors called for more research on the causality of their findings.