The occurrence of urinary stones is age-related. Different ages will produce stones with different characteristics, and the relationship between age and stones may be different in different regions, and the age characteristics of stones are also different between men and women.
In 2005, Daudon used infrared spectroscopy to analyze the sex ratio of 10,617 stones in France with a ratio of 2.20:1, pointing out that the occurrence of uric acid stones increased with age in both men and women, and found that calcium phosphate stones were higher in young women than in older women (30.8% in the 30-39 years old stage, 7.0% in the 60-69 years old stage, P<0.0001), while the difference was not obvious in male patients.
Conversely, there is a clear peak in the age distribution of infectious stones: 27.7% of female patients are aged 30-39 years and 25.2% are aged 60-69 years, and 25.2% of male patients are aged 60-69 years and 7.2% are aged 40-49 years. Among the uric acid stone patients, the proportion of male and female patients was as high as 4.53, and the distribution of male and female patients was mostly in the elderly age group, 27.4% and 25.6% were located in the age group of 60-69 years old, while only 5.2% and 4.4% were distributed in the age group of 30-39 years. Among all patients, COM and COD stones were mostly located in the middle age group of 30-60 years, although the distribution of COD stones in male patients was higher in 30-39 years (30.8%) than in 40-49 years (22.8%, P<0.001). Stones with COD as the main component decline after the age of 49, and after the age of 60, male patients decline faster than women.
Daudon reported that calcium oxalate dihydrate stones were the main component of calculi in five different age groups, and the proportion of calcium oxalate stones dihydrate in young patients was higher than that in older patients, regardless of gender differences. However, after the peak of calcium oxalate stones dihydrate in the male group of 20-29 years, the proportion of calcium oxalate stones in the male group is higher than that of women, decreasing by about 5% per decade, and calcium oxalate stones dihydrate in women (between 50 and 80 years of age) decreasing by about 3% per decade. The reason why calcium oxalate stones dihydrate decline with age after reaching their peak may be related to the decrease in urinary calcium excretion with age. In women aged 50 to 79 years, the proportion of calcium oxalate stones dihydrate decreases more slowly, probably due to menopause, calcium and vitamin D supplementation is often recommended to prevent osteoporosis, resulting in hypercalciuria in at least some patients and calcium oxalate stones dihydrate in menopausal women. The male-to-female ratio changes with the composition of the stones.
Robertson et al. reported that the peak age of urinary tract stones in the UK is between 40 and 50 years old, while the peak age of uric acid stones is more than 60 years. Japanese researchers Koide et al. reported that the peak incidence of urinary tract stones in Japan was 40 to 50 years old, and the peak incidence of calcium oxalate stones dihydrate was 30 to 40 years old. The peak incidence of uric acid stones in males and females is between the ages of 60 and 70 years, and the sex ratio is 4.6. The composition ratio of uric acid stones increases with age. Anhydrous uric acid stones have been shown to be associated with hyperuricuria, acidic urine, and oligouria, and acidic urine is predominant. The positive correlation between the proportion of anhydrous uric acid stones and age is related to the weakening of tubular ammonia with age, which can cause a progressive decrease in urinary pH.
Abate et al. reported that insulin resistance in metabolic syndrome is associated with low ammonia in the urine and low urine pH that increases the risk of uric acid stone formation. Epidemiological surveys in the United States indicate that metabolic syndrome is highly prevalent in the elderly population. Therefore, insulin resistance may be another common cause of uric acid stones in the elderly population. Ammonium urate stones occur in children in developing countries. Ammonium urate stones are associated with dietary phosphorus deficiency, and are rare in both mainland and developed countries due to a balanced diet, but are still common in children in some developing countries. Ammonium urate stones are endemic in Asia, pure AAU stones have almost been eliminated in developed countries, but they can be combined with other stones in mixed stones, ammonium urate stones are most often mixed with uric acid, followed by struvite and calcium oxalate. The incidence of metabolic syndrome increases with age, both in men and women, and can reach up to 40% in people over 60 years of age. Due to the rapid increase in the incidence of metabolic syndrome in Western countries, metabolic syndrome has become a pathogenic factor for aciduria and uric acid kidney stones in old age. From a practical point of view, screening patients with metabolic syndrome, especially those who are overweight or hypertensive, is a good clinical practice for finding uric acid stones.
The incidence of urinary tract stones in children is about 3%, which is only equivalent to 1/50 or 1/70 of the incidence rate in adults, but urinary tract stones in children are mostly accompanied by factors such as metabolic disorders or congenital malformations, and the stones grow quickly and have a high recurrence rate. In developed countries, kidney stones are more common in children, and calcium oxalate stones are more common in developing countries, and bladder stones are more common in children, and ammonium urate is mostly used in developing countries. In developed countries, the main urinary tract stones in children are upper urinary tract stones, and the proportion of lower urinary tract stones in children in the United Kingdom and Greece is not more than 10%, however, lower urinary tract stones are still common in developing countries, such as 24% in Tunisia, 31% in Pakistan, and even more than 80% in some parts of India, and the proportion of lower urinary tract stones in children in China is about 11%, which is lower than that in other developing countries. The composition of stone composition in Chinese children is similar to that reported in countries such as Pakistan, Tunisia and Armenia. The ratio of boys to girls in China is about 2.93:1, and urolithiasis is more common in young children under the age of 3, about 21% under the age of 2, and about 42% under the age of 5. In most developing countries, calcium oxalate stones remain the most common type of stone in children. Cystine stones account for 1% to 5% of childhood stones in developed and developing countries, 6% to 16% of childhood stones in developing countries, and 15% to 20% in developed countries. The proportion of children infected with stones in China is low, less than 3%. Antibiotic misuse is a common phenomenon in China, which may reduce the incidence of urinary tract infections, so the low rate of infected stones among children in China may be the result of antibiotic misuse. Ammonium urate stones in children account for about 4.52% of all stones in children in China, which is significantly lower than the data of 27.2% in Pakistan. Compared to Pakistan, Chinese children have a more balanced diet, which reduces the occurrence of ammonium urate stones. In Pakistan, nutritional deficiencies, low-protein diets, and high-carbohydrate diets contribute to the high rates of ammonium urate stones. Tables 5-10 show the composition of stone composition in children in some countries at different times. Cystine stones, the detection rate of cystine stones is 1.18%. It is concentrated in children, accounting for 9% of children's stones. Cystine stones are caused by congenital cystinuria and are inherited in an autosomal recessive manner. Cystine stones account for about 1%~2% of all urinary tract stones, which are related to amino acid transporter defects, and the precipitation of stones in an acidic environment requires a long time of treatment.