The influence of age and gender on niacin skin test results - implications for the use as a biochemical marker in schizophrenia.

Investigation of abnormal skin response to niacin (vitamin B3) stimulation has gained increasing interest in schizophrenia research during last years. However, current efforts to implement niacin tests in routine diagnostics are jeopardised by wide inter-individual variations of skin response. We investigated age and gender as potential factors of influence on niacin sensitivity in 117 healthy subjects (63 male, 54 female). Niacin was applied in three dilution steps (0.1, 0.01, 0.001 M) onto the inner forearm skin. Skin reaction was assessed in three minute intervals over 15 min using optical reflection spectroscopy. Males displayed a significantly weaker flush response than females. The rate of non-responders at the lowest concentration was about twice as high in men than women. Significant negative correlations between age and niacin sensitivity were revealed for both sexes. Age and gender considerably influence niacin sensitivity, possibly due to the effects of sex hormones on vasomotor function and prostaglandin metabolism. Consideration of gender and age is strongly recommended for further clinical niacin studies.