Objective: To evaluate diabetes mellitus as a risk factor for pancreatic cancer with the consideration that diabetes may also be a consequence of pancreatic cancer.
Data sources: Pertinent studies of diabetes mellitus and pancreatic cancer published between 1975 and 1994 were identified from a MEDLINE search and from citations in articles and books.
Study selection: Twenty of a total of 30 case-control and cohort studies met the two inclusion criteria: cases with a duration of diabetes of at least 1 year prior to either pancreatic cancer diagnosis or death and the ability to calculate an appropriate relative risk (RR) estimate and variance.
Data extraction and synthesis: The pooled RR and 95% confidence interval (CI) of pancreatic cancer for diabetics relative to nondiabetics was 2.1 (1.6 to 2.8). There was a tendency for a higher RR for the nine cohort studies (RR, 2.6; 95% CI, 1.6 to 4.1) than for the 11 case-control studies (RR, 1.8; 95% CI, 1.1 to 2.7). Requiring diabetes duration of at least 5 years resulted in an RR of 2.0 (95% CI, 1.2 to 3.2).
Conclusion: Pancreatic cancer occurs with increased frequency among persons with long-standing diabetes.