Critical appraisal of the recent data published on the link between insulin and cancer

Recent publications indicate a possible association between newer analogue insulin Glargine and cancer. However all these data were observational in nature and subject to lot of methodological errors. It is practically impossible to derive at a cause and effect relationship based on these observational studies. There are several confounding factors like hyperinsulinemia, obesity and smoking, which independently can be associated with cancer risk. This review looks into the recently published observational studies from the methodological point of view and whether such a negative association can indeed be drawn as a conclusion. Several methodological defects were identified in the process of scrutiny and we concluded it is not possible to conclude that there is an association between Glargine use and cancer. However long-term prospective data is required to come to definite conclusion.