One of the important benefits of early screening for gallstone disease is that ultrasonography can detect asymptomatic cases, which results in early treatment and the prevention of serious outcomes such as acute gallstone pancreatitis and gallbladder cancer[15
]. However, few reports on the prevalence and possible etiology of gallstone disease have been published in China. In the present study, gallstone disease appeared to be common in the test population, i.e. an estimated 10.7% of the test population in Chengdu, China, had gallstone disease. The reported prevalence of gallstone disease is approximately 3.6% in Japan and 4.3%-5.0% in Taiwan[16–18
]. The apparently higher prevalence rate in our study may have been due to the Westernized lifestyle of our patients, who were of middle-to-high income class. Another possible reason for such differences has been related to the fact that this was a hospital-based study which was unlikely the population study that could represent the general population.
The present study, in accordance with reports from Western countries and other regions of Asia, showed that an older age is a significant risk factor for gallstone disease[16,18,19
]. In contrast, gallstone disease is virtually absent in children and adolescents aged 8-19 years[20
]. Long-term exposure to many risk factors, as is true for the elderly, may increase the risk of gallstone disease. At the same time, sedentary activity, which is greater in the elderly than in younger populations, may also increase the risk of gallstone disease[21,22
]. Furthermore, gallstone disease is also an acquired disease influenced by chronic environmental factors plus an aging effect[23
In concordance with the findings of previous studies, female sex was also a major risk factor for gallstone disease in the present study. The commonly perceived opinion that women are at greater risk of developing gallstone disease than men may largely be due to extraneous risk factors, such as pregnancy and sex hormones. The number of pregnancies is the main one related to the high rates of gallstone disease in women. Sex hormones are most likely to be responsible for the increased risk. Estrogen increases biliary cholesterol secretion causing cholesterol super saturation of bile. Thus, hormone replacement therapy in postmenopausal women has been described to be associated with an increased risk for gallstone disease[24,25
]. Some studies have also shown a relation between oral contraceptive use and a high prevalence of gallstone disease[26,27
Previous population studies have reported inconsistent associations of DM with gallstone disease. A study in Rome showed that DM was associated with an increased risk of gallstone disease in men and women separately[28
]. A study of Hispanic Americans found a positive association between DM and self-reported gallstone disease in women, but not in men[26
]. A study in Italy failed to find any relation between DM and gallstone disease in men and women combined[29
]. The present analyses showed a positive association between DM and gallstone disease in men, but not in women. The mechanism underlying the relation of DM with gallstone disease may be fasting hyperinsulinemia, which can overly activate the rate-limiting enzyme for cholesterol synthesis[30
] and finally leads to cholesterol saturation in the bile. Reduced motility of the gallbladder in persons with diabetes is another possible explanation[31,32
In our study, obesity only showed a positive association with gallstone disease in women. Previous studies have found disparate findings for BMI or relative weight in men with gallstone disease[29,33,34
]. However, three population screening surveys using ultrasonography failed to find a positive association between BMI and gallstone disease in men in Italy, Denmark, and the United States[26,35,36
], whereas all three showed a positive association in women. The discrepant findings for BMI in men with gallstone disease have not been fully explained. A possible reason for these findings may be that BMI is not a suitable standard of obesity in men. Waist-to-hip ratio may be a better measure of obesity. The mechanism responsible for the increased risk of gallstone disease in obese persons may be the increase in bile saturation that results from an increase in the biliary secretion of cholesterol, which likely depends on the higher synthesis rate of cholesterol in obese persons[23
The present study showed that hypertriglyceridemia was a risk factor for gallstone disease only in women. However, high total cholesterol, low HDL-C, and high LDL-C levels were negatively associated with the risk of gallstone disease in both men and women. The present finding is different from that of previous studies, which noted a positive relation between hypertriglyceridemia and gallstone disease[36
]. However, a cross-sectional study in Denmark failed to find a significant association between gallstone disease and plasma lipid levels (including triglyceride, total cholesterol, HDL-C, and LDL-C)[37
]. Further studies are needed to clarify whether elevated levels of plasma lipids are independent risk factors for gallstone disease.
A major limitation of the present study was the potential self-selection bias due to the hospital-based study design, which resulted in a sample that was not representative of the general population in western China. However, we believe that our findings are useful as background data for future studies of the epidemiology of gallstone disease in China. Second, our measurements were inadequate. Some factors that might play an important role in gallstone disease development, such as oral contraceptive use and waist-to-hip ratio, were not collected in detail. Third, measurement error and different pathogenicities may have occurred, because the measurements were only made at one time point. Therefore, future studies need to determine whether these factors affect the results of our study.
In conclusion, older age, and female sex are associated with the prevalence of gallstone disease in both men and women. Obesity and hypertriglyceridemia were positively associated with gallstone disease in women, but not in men, whereas DM (FPG ≥ 1260 mg/L) was positively associated with gallstone disease only in men.