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Risk factors
A number of factors put people at higher risk of gallstones:
Gender: The prevalence of gallstones is higher in women than in men; indeed, studies have shown that gallstone disease is common in young women but rare in young men. Women between the ages of 20 and 60 are three times more likely to develop gallstones than are men in the same age group. And by age 60, 20 percent of American women have gallstones.
One key explanation for the gender difference is that estrogen increases the concentration of cholesterol in bile, leading to an excess of cholesterol and slowed gallbladder movement. During pregnancy, women are especially vulnerable, and multiple pregnancies increase a woman's risk. The estrogen in oral contraceptives and hormone replacement therapy has the same impact on bile and gallbladder movement.
Age: The incidence of gallstone disease increases with age. Generally, young people under age 20 who suffer from gallstones have underlying conditions such as cystic fibrosis. The likelihood of developing gallstones increases after age 60.
Genetics: Family history and ethnicity are critical risk factors in development of gallstones, though no gene responsible for gallstone formation has yet been discovered.
American Indians are at particular risk, because they are known to secrete high levels of cholesterol in bile. A majority of American Indian men have gallstones by age 60, and among Pima Indian women, 70 percent will have gallstones by age 30. Hispanics and Mexican-Americans, particularly women, also have high rates of gallstone disease. And both men and women from Norway and Chile suffer increased rates of gallstone disease.
African-Americans seem to have lower rates of gallstone disease than American Indians, whites, or Hispanics.
Obesity: Obesity is a significant risk factor, particularly for women. Women with a body mass index of over 30--in the obese range--have twice the risk of gallstone disease of women who are not overweight. One explanation for the link between obesity and gallstones is that the overweight condition tends to upset the balance between cholesterol and other components of bile, either by reducing the other components relative to cholesterol or by causing excessive secretion of cholesterol into the bile. Obesity also slows down the emptying of the gallbladder.
Location of body fat: Belly fat, that spare tire around the middle, dramatically increases the chance of developing stones. One recent study of 42,000 healthy nurses showed that when women put on weight around their waists, the risk of developing gallstone disease requiring surgery nearly doubled.
Diabetes: People with diabetes often have high levels of triglycerides in their blood, and these fatty acids tend to increase the risk of gallstones.
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