Relationship between changes in haemoglobin A1C and prostate-specific antigen in healthy men

BackgroundAlthough 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 A1C (HbA1C) 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 HbA1C were associated with PSA levels, independent of plasma volume changes, as indicated by haematocrit and weight.MethodsWe 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 HbA1C and PSA over 1 year.ResultsAdjusting for age, body mass index at baseline and changes in weight and haematocrit, the increases in HbA1C and PSA were concordant (5.7% increase per 1-unit HbA1C change; 95% confidence interval, 2.8–8.5%; p < 0.001).ConclusionsIn contrast to previous cross-sectional observations showing an inverse association between HbA1C and PSA, longitudinal observations suggest a positive association between the two. Further studies are needed to investigate the association between diabetes and prostate cancer.