Most people experience a gradual decline in kidney function as they age. Renal blood flow decreases by about 10% every 10 years after the age of 40, and is only half of that of young people by the age of 90; glomerular filtration rate decreases by about 8 ml/min every 10 years, and the decline is more pronounced after the age of 50. Increased nocturia in the elderly is one of the manifestations of declining renal tubular function, in addition to being partly caused by other diseases. Therefore, elderly people must pay attention to avoid various factors that may add to kidney damage to avoid adding to the fragile kidneys.