[The effect of the interval from dinner until retiring on the concentration of lithogenic substances during sleep]

The relationship between the interval from dinner until retiring and the concentration of various substances secreted into the urine during sleep was studied in 69 healthy men who had eaten the same meal. The specific gravity and the concentrations of creatinine, uric acid and magnesium in the morning spot urine were highest in subjects who had retired within 2 hours after dinner. The concentrations of calcium and oxalate in the morning spot urine were highest in those who had retired between 2 and 4 hours. The specific gravity and urinary concentrations of creatinine, uric acid and oxalate were markedly higher in those with the interval less than 4 hours than in those 4 hours or longer. The concentrations of calcium, magnesium and citrate were not significantly different between the two groups. From these results, we recommend that the interval from dinner until retiring be prolonged and fluid be drunk before going to bed to decrease the concentration of lithogenic substances during sleep.