Relationship between changes in haemoglobin A(1C) and prostate-specific antigen in healthy men

Background: Although many studies have shown an inverse relationship between diabetes and prostate cancer, it still remains unclear why diabetes may reduce the risk of prostate cancer. An inverse association between haemoglobin A(1C) (HbA(1C)) and prostate-specific antigen (PSA) also has been reported in previous studies that assessed the association cross-sectionally. To fully understand the relationship between diabetes and prostate cancer, it is essential to examine the association in a longitudinal design. The effect of plasma volume should also be considered in examining the PSA level. The aim of this study was to determine whether changes in HbA(1C) were associated with PSA levels, independent of plasma volume changes, as indicated by haematocrit and weight. Methods: We investigated 5917 Japanese men aged 50 and over who visited St. Luke's International Hospital, Tokyo for routine health check-ups in 2006 and 2007. We performed a multiple linear regression analysis to examine any association between changes in HbA(1C) and PSA over 1 year. Results: Adjusting for age, body mass index at baseline and changes in weight and haematocrit, the increases in HbA(1C) and PSA were concordant (5.7% increase per 1-unit HbA(1C) change; 95% confidence interval, 2.8-8.5%; p <0.001). Conclusions: In contrast to previous cross-sectional observations showing an inverse association between HbA(1C) and PSA, longitudinal observations suggest a positive association between the two. Further studies are needed to investigate the association between diabetes and prostate cancer. (C) 2010 Elsevier Ltd. All rights reserved.